1 /*
   2  * Copyright (c) 1994, 2024, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package java.lang;
  26 
  27 import java.io.BufferedInputStream;
  28 import java.io.BufferedOutputStream;
  29 import java.io.Console;
  30 import java.io.FileDescriptor;
  31 import java.io.FileInputStream;
  32 import java.io.FileOutputStream;
  33 import java.io.IOException;
  34 import java.io.InputStream;
  35 import java.io.OutputStream;
  36 import java.io.PrintStream;
  37 import java.lang.annotation.Annotation;
  38 import java.lang.foreign.MemorySegment;
  39 import java.lang.invoke.MethodHandle;
  40 import java.lang.invoke.MethodType;
  41 import java.lang.module.ModuleDescriptor;
  42 import java.lang.reflect.ClassFileFormatVersion;
  43 import java.lang.reflect.Executable;
  44 import java.lang.reflect.Method;
  45 import java.net.URI;
  46 import java.nio.channels.Channel;
  47 import java.nio.channels.spi.SelectorProvider;
  48 import java.nio.charset.CharacterCodingException;
  49 import java.nio.charset.Charset;
  50 import java.security.ProtectionDomain;
  51 import java.util.List;
  52 import java.util.Locale;
  53 import java.util.Map;
  54 import java.util.Objects;
  55 import java.util.Properties;
  56 import java.util.ResourceBundle;
  57 import java.util.Set;
  58 import java.util.concurrent.Executor;
  59 import java.util.concurrent.ScheduledExecutorService;
  60 import java.util.function.Supplier;
  61 import java.util.concurrent.ConcurrentHashMap;
  62 import java.util.stream.Stream;
  63 
  64 import jdk.internal.javac.Restricted;
  65 import jdk.internal.loader.NativeLibraries;
  66 import jdk.internal.logger.LoggerFinderLoader.TemporaryLoggerFinder;
  67 import jdk.internal.misc.Blocker;
  68 import jdk.internal.misc.CarrierThreadLocal;
  69 import jdk.internal.util.StaticProperty;
  70 import jdk.internal.module.ModuleBootstrap;
  71 import jdk.internal.module.ServicesCatalog;
  72 import jdk.internal.reflect.CallerSensitive;
  73 import jdk.internal.reflect.Reflection;
  74 import jdk.internal.access.JavaLangAccess;
  75 import jdk.internal.access.SharedSecrets;
  76 import jdk.internal.logger.LoggerFinderLoader;
  77 import jdk.internal.logger.LazyLoggers;
  78 import jdk.internal.logger.LocalizedLoggerWrapper;
  79 import jdk.internal.misc.VM;
  80 import jdk.internal.util.SystemProps;
  81 import jdk.internal.vm.Continuation;
  82 import jdk.internal.vm.ContinuationScope;
  83 import jdk.internal.vm.StackableScope;
  84 import jdk.internal.vm.ThreadContainer;
  85 import jdk.internal.vm.annotation.IntrinsicCandidate;
  86 import jdk.internal.vm.annotation.Stable;
  87 import sun.reflect.annotation.AnnotationType;
  88 import sun.nio.ch.Interruptible;
  89 import sun.nio.cs.UTF_8;
  90 
  91 /**
  92  * The {@code System} class contains several useful class fields
  93  * and methods. It cannot be instantiated.
  94  *
  95  * Among the facilities provided by the {@code System} class
  96  * are standard input, standard output, and error output streams;
  97  * access to externally defined properties and environment
  98  * variables; a means of loading files and libraries; and a utility
  99  * method for quickly copying a portion of an array.
 100  *
 101  * @since   1.0
 102  */
 103 public final class System {
 104     /* Register the natives via the static initializer.
 105      *
 106      * The VM will invoke the initPhase1 method to complete the initialization
 107      * of this class separate from <clinit>.
 108      */
 109     private static native void registerNatives();
 110     static {
 111         registerNatives();
 112     }
 113 
 114     /** Don't let anyone instantiate this class */
 115     private System() {
 116     }
 117 
 118     /**
 119      * The "standard" input stream. This stream is already
 120      * open and ready to supply input data. Typically this stream
 121      * corresponds to keyboard input or another input source specified by
 122      * the host environment or user. In case this stream is wrapped
 123      * in a {@link java.io.InputStreamReader}, {@link Console#charset()}
 124      * should be used for the charset, or consider using
 125      * {@link Console#reader()}.
 126      *
 127      * @see Console#charset()
 128      * @see Console#reader()
 129      */
 130     public static final InputStream in = null;
 131 
 132     /**
 133      * The "standard" output stream. This stream is already
 134      * open and ready to accept output data. Typically this stream
 135      * corresponds to display output or another output destination
 136      * specified by the host environment or user. The encoding used
 137      * in the conversion from characters to bytes is equivalent to
 138      * {@link ##stdout.encoding stdout.encoding}.
 139      * <p>
 140      * For simple stand-alone Java applications, a typical way to write
 141      * a line of output data is:
 142      * <blockquote><pre>
 143      *     System.out.println(data)
 144      * </pre></blockquote>
 145      * <p>
 146      * See the {@code println} methods in class {@code PrintStream}.
 147      *
 148      * @see     java.io.PrintStream#println()
 149      * @see     java.io.PrintStream#println(boolean)
 150      * @see     java.io.PrintStream#println(char)
 151      * @see     java.io.PrintStream#println(char[])
 152      * @see     java.io.PrintStream#println(double)
 153      * @see     java.io.PrintStream#println(float)
 154      * @see     java.io.PrintStream#println(int)
 155      * @see     java.io.PrintStream#println(long)
 156      * @see     java.io.PrintStream#println(java.lang.Object)
 157      * @see     java.io.PrintStream#println(java.lang.String)
 158      * @see     ##stdout.encoding stdout.encoding
 159      */
 160     public static final PrintStream out = null;
 161 
 162     /**
 163      * The "standard" error output stream. This stream is already
 164      * open and ready to accept output data.
 165      * <p>
 166      * Typically this stream corresponds to display output or another
 167      * output destination specified by the host environment or user. By
 168      * convention, this output stream is used to display error messages
 169      * or other information that should come to the immediate attention
 170      * of a user even if the principal output stream, the value of the
 171      * variable {@code out}, has been redirected to a file or other
 172      * destination that is typically not continuously monitored.
 173      * The encoding used in the conversion from characters to bytes is
 174      * equivalent to {@link ##stderr.encoding stderr.encoding}.
 175      *
 176      * @see     ##stderr.encoding stderr.encoding
 177      */
 178     public static final PrintStream err = null;
 179 
 180     // Initial values of System.in and System.err, set in initPhase1().
 181     private static @Stable InputStream initialIn;
 182     private static @Stable PrintStream initialErr;
 183 
 184     // `sun.jnu.encoding` if it is not supported. Otherwise null.
 185     // It is initialized in `initPhase1()` before any charset providers
 186     // are initialized.
 187     private static String notSupportedJnuEncoding;
 188 
 189     /**
 190      * Reassigns the "standard" input stream.
 191      *
 192      * @param in the new standard input stream.
 193      *
 194      * @since   1.1
 195      */
 196     public static void setIn(InputStream in) {
 197         setIn0(in);
 198     }
 199 
 200     /**
 201      * Reassigns the "standard" output stream.
 202      *
 203      * @param out the new standard output stream
 204      *
 205      * @since   1.1
 206      */
 207     public static void setOut(PrintStream out) {
 208         setOut0(out);
 209     }
 210 
 211     /**
 212      * Reassigns the "standard" error output stream.
 213      *
 214      * @param err the new standard error output stream.
 215      *
 216      * @since   1.1
 217      */
 218     public static void setErr(PrintStream err) {
 219         setErr0(err);
 220     }
 221 
 222     private static volatile Console cons;
 223 
 224     /**
 225      * Returns the unique {@link java.io.Console Console} object associated
 226      * with the current Java virtual machine, if any.
 227      *
 228      * @return  The system console, if any, otherwise {@code null}.
 229      *
 230      * @since   1.6
 231      */
 232      public static Console console() {
 233          Console c;
 234          if ((c = cons) == null) {
 235              synchronized (System.class) {
 236                  if ((c = cons) == null) {
 237                      cons = c = SharedSecrets.getJavaIOAccess().console();
 238                  }
 239              }
 240          }
 241          return c;
 242      }
 243 
 244     /**
 245      * Returns the channel inherited from the entity that created this
 246      * Java virtual machine.
 247      *
 248      * This method returns the channel obtained by invoking the
 249      * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
 250      * inheritedChannel} method of the system-wide default
 251      * {@link java.nio.channels.spi.SelectorProvider} object.
 252      *
 253      * <p> In addition to the network-oriented channels described in
 254      * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
 255      * inheritedChannel}, this method may return other kinds of
 256      * channels in the future.
 257      *
 258      * @return  The inherited channel, if any, otherwise {@code null}.
 259      *
 260      * @throws  IOException
 261      *          If an I/O error occurs
 262      *
 263      * @since 1.5
 264      */
 265     public static Channel inheritedChannel() throws IOException {
 266         return SelectorProvider.provider().inheritedChannel();
 267     }
 268 
 269     private static native void setIn0(InputStream in);
 270     private static native void setOut0(PrintStream out);
 271     private static native void setErr0(PrintStream err);
 272 
 273     /**
 274      * Throws {@code UnsupportedOperationException}. Setting a security manager
 275      * is not supported.
 276      *
 277      * @param  sm ignored
 278      * @throws UnsupportedOperationException always
 279      * @see #getSecurityManager
 280      * @deprecated This method originally set
 281      *       {@linkplain SecurityManager the system-wide Security Manager}.
 282      *       Setting a Security Manager is no longer supported. There is no
 283      *       replacement for the Security Manager or this method.
 284      */
 285     @Deprecated(since="17", forRemoval=true)
 286     public static void setSecurityManager(@SuppressWarnings("removal") SecurityManager sm) {
 287         throw new UnsupportedOperationException(
 288                  "Setting a Security Manager is not supported");
 289     }
 290 
 291     /**
 292      * Returns {@code null}. Setting a security manager is not supported.
 293      *
 294      * @return  {@code null}
 295      * @see     #setSecurityManager
 296      * @deprecated This method originally returned
 297      *       {@linkplain SecurityManager the system-wide Security Manager}.
 298      *       Setting a Security Manager is no longer supported. There is no
 299      *       replacement for the Security Manager or this method.
 300      */
 301     @SuppressWarnings("removal")
 302     @Deprecated(since="17", forRemoval=true)
 303     public static SecurityManager getSecurityManager() {
 304         return null;
 305     }
 306 
 307     /**
 308      * Returns the current time in milliseconds.  Note that
 309      * while the unit of time of the return value is a millisecond,
 310      * the granularity of the value depends on the underlying
 311      * operating system and may be larger.  For example, many
 312      * operating systems measure time in units of tens of
 313      * milliseconds.
 314      *
 315      * <p> See the description of the class {@code Date} for
 316      * a discussion of slight discrepancies that may arise between
 317      * "computer time" and coordinated universal time (UTC).
 318      *
 319      * @return  the difference, measured in milliseconds, between
 320      *          the current time and midnight, January 1, 1970 UTC.
 321      * @see     java.util.Date
 322      */
 323     @IntrinsicCandidate
 324     public static native long currentTimeMillis();
 325 
 326     /**
 327      * Returns the current value of the running Java Virtual Machine's
 328      * high-resolution time source, in nanoseconds.
 329      *
 330      * This method can only be used to measure elapsed time and is
 331      * not related to any other notion of system or wall-clock time.
 332      * The value returned represents nanoseconds since some fixed but
 333      * arbitrary <i>origin</i> time (perhaps in the future, so values
 334      * may be negative).  The same origin is used by all invocations of
 335      * this method in an instance of a Java virtual machine; other
 336      * virtual machine instances are likely to use a different origin.
 337      *
 338      * <p>This method provides nanosecond precision, but not necessarily
 339      * nanosecond resolution (that is, how frequently the value changes)
 340      * - no guarantees are made except that the resolution is at least as
 341      * good as that of {@link #currentTimeMillis()}.
 342      *
 343      * <p>Differences in successive calls that span greater than
 344      * approximately 292 years (2<sup>63</sup> nanoseconds) will not
 345      * correctly compute elapsed time due to numerical overflow.
 346      *
 347      * <p>The values returned by this method become meaningful only when
 348      * the difference between two such values, obtained within the same
 349      * instance of a Java virtual machine, is computed.
 350      *
 351      * <p>For example, to measure how long some code takes to execute:
 352      * <pre> {@code
 353      * long startTime = System.nanoTime();
 354      * // ... the code being measured ...
 355      * long elapsedNanos = System.nanoTime() - startTime;}</pre>
 356      *
 357      * <p>To compare elapsed time against a timeout, use <pre> {@code
 358      * if (System.nanoTime() - startTime >= timeoutNanos) ...}</pre>
 359      * instead of <pre> {@code
 360      * if (System.nanoTime() >= startTime + timeoutNanos) ...}</pre>
 361      * because of the possibility of numerical overflow.
 362      *
 363      * @return the current value of the running Java Virtual Machine's
 364      *         high-resolution time source, in nanoseconds
 365      * @since 1.5
 366      */
 367     @IntrinsicCandidate
 368     public static native long nanoTime();
 369 
 370     /**
 371      * Copies an array from the specified source array, beginning at the
 372      * specified position, to the specified position of the destination array.
 373      * A subsequence of array components are copied from the source
 374      * array referenced by {@code src} to the destination array
 375      * referenced by {@code dest}. The number of components copied is
 376      * equal to the {@code length} argument. The components at
 377      * positions {@code srcPos} through
 378      * {@code srcPos+length-1} in the source array are copied into
 379      * positions {@code destPos} through
 380      * {@code destPos+length-1}, respectively, of the destination
 381      * array.
 382      * <p>
 383      * If the {@code src} and {@code dest} arguments refer to the
 384      * same array object, then the copying is performed as if the
 385      * components at positions {@code srcPos} through
 386      * {@code srcPos+length-1} were first copied to a temporary
 387      * array with {@code length} components and then the contents of
 388      * the temporary array were copied into positions
 389      * {@code destPos} through {@code destPos+length-1} of the
 390      * destination array.
 391      * <p>
 392      * If {@code dest} is {@code null}, then a
 393      * {@code NullPointerException} is thrown.
 394      * <p>
 395      * If {@code src} is {@code null}, then a
 396      * {@code NullPointerException} is thrown and the destination
 397      * array is not modified.
 398      * <p>
 399      * Otherwise, if any of the following is true, an
 400      * {@code ArrayStoreException} is thrown and the destination is
 401      * not modified:
 402      * <ul>
 403      * <li>The {@code src} argument refers to an object that is not an
 404      *     array.
 405      * <li>The {@code dest} argument refers to an object that is not an
 406      *     array.
 407      * <li>The {@code src} argument and {@code dest} argument refer
 408      *     to arrays whose component types are different primitive types.
 409      * <li>The {@code src} argument refers to an array with a primitive
 410      *    component type and the {@code dest} argument refers to an array
 411      *     with a reference component type.
 412      * <li>The {@code src} argument refers to an array with a reference
 413      *    component type and the {@code dest} argument refers to an array
 414      *     with a primitive component type.
 415      * </ul>
 416      * <p>
 417      * Otherwise, if any of the following is true, an
 418      * {@code IndexOutOfBoundsException} is
 419      * thrown and the destination is not modified:
 420      * <ul>
 421      * <li>The {@code srcPos} argument is negative.
 422      * <li>The {@code destPos} argument is negative.
 423      * <li>The {@code length} argument is negative.
 424      * <li>{@code srcPos+length} is greater than
 425      *     {@code src.length}, the length of the source array.
 426      * <li>{@code destPos+length} is greater than
 427      *     {@code dest.length}, the length of the destination array.
 428      * </ul>
 429      * <p>
 430      * Otherwise, if any actual component of the source array from
 431      * position {@code srcPos} through
 432      * {@code srcPos+length-1} cannot be converted to the component
 433      * type of the destination array by assignment conversion, an
 434      * {@code ArrayStoreException} is thrown. In this case, let
 435      * <b><i>k</i></b> be the smallest nonnegative integer less than
 436      * length such that {@code src[srcPos+}<i>k</i>{@code ]}
 437      * cannot be converted to the component type of the destination
 438      * array; when the exception is thrown, source array components from
 439      * positions {@code srcPos} through
 440      * {@code srcPos+}<i>k</i>{@code -1}
 441      * will already have been copied to destination array positions
 442      * {@code destPos} through
 443      * {@code destPos+}<i>k</I>{@code -1} and no other
 444      * positions of the destination array will have been modified.
 445      * (Because of the restrictions already itemized, this
 446      * paragraph effectively applies only to the situation where both
 447      * arrays have component types that are reference types.)
 448      *
 449      * @param      src      the source array.
 450      * @param      srcPos   starting position in the source array.
 451      * @param      dest     the destination array.
 452      * @param      destPos  starting position in the destination data.
 453      * @param      length   the number of array elements to be copied.
 454      * @throws     IndexOutOfBoundsException  if copying would cause
 455      *             access of data outside array bounds.
 456      * @throws     ArrayStoreException  if an element in the {@code src}
 457      *             array could not be stored into the {@code dest} array
 458      *             because of a type mismatch.
 459      * @throws     NullPointerException if either {@code src} or
 460      *             {@code dest} is {@code null}.
 461      */
 462     @IntrinsicCandidate
 463     public static native void arraycopy(Object src,  int  srcPos,
 464                                         Object dest, int destPos,
 465                                         int length);
 466 
 467     /**
 468      * Returns the same hash code for the given object as
 469      * would be returned by the default method hashCode(),
 470      * whether or not the given object's class overrides
 471      * hashCode().
 472      * The hash code for the null reference is zero.
 473      *
 474      * @param x object for which the hashCode is to be calculated
 475      * @return  the hashCode
 476      * @since   1.1
 477      * @see Object#hashCode
 478      * @see java.util.Objects#hashCode(Object)
 479      */
 480     @IntrinsicCandidate
 481     public static native int identityHashCode(Object x);
 482 
 483     /**
 484      * System properties.
 485      *
 486      * See {@linkplain #getProperties getProperties} for details.
 487      */
 488     private static Properties props;
 489 
 490     /**
 491      * Determines the current system properties.
 492      * <p>
 493      * The current set of system properties for use by the
 494      * {@link #getProperty(String)} method is returned as a
 495      * {@code Properties} object. If there is no current set of
 496      * system properties, a set of system properties is first created and
 497      * initialized. This set of system properties includes a value
 498      * for each of the following keys unless the description of the associated
 499      * value indicates that the value is optional.
 500      * <table class="striped" style="text-align:left">
 501      * <caption style="display:none">Shows property keys and associated values</caption>
 502      * <thead>
 503      * <tr><th scope="col">Key</th>
 504      *     <th scope="col">Description of Associated Value</th></tr>
 505      * </thead>
 506      * <tbody>
 507      * <tr><th scope="row">{@systemProperty java.version}</th>
 508      *     <td>Java Runtime Environment version, which may be interpreted
 509      *     as a {@link Runtime.Version}</td></tr>
 510      * <tr><th scope="row">{@systemProperty java.version.date}</th>
 511      *     <td>Java Runtime Environment version date, in ISO-8601 YYYY-MM-DD
 512      *     format, which may be interpreted as a {@link
 513      *     java.time.LocalDate}</td></tr>
 514      * <tr><th scope="row">{@systemProperty java.vendor}</th>
 515      *     <td>Java Runtime Environment vendor</td></tr>
 516      * <tr><th scope="row">{@systemProperty java.vendor.url}</th>
 517      *     <td>Java vendor URL</td></tr>
 518      * <tr><th scope="row">{@systemProperty java.vendor.version}</th>
 519      *     <td>Java vendor version <em>(optional)</em> </td></tr>
 520      * <tr><th scope="row">{@systemProperty java.home}</th>
 521      *     <td>Java installation directory</td></tr>
 522      * <tr><th scope="row">{@systemProperty java.vm.specification.version}</th>
 523      *     <td>Java Virtual Machine specification version, whose value is the
 524      *     {@linkplain Runtime.Version#feature feature} element of the
 525      *     {@linkplain Runtime#version() runtime version}</td></tr>
 526      * <tr><th scope="row">{@systemProperty java.vm.specification.vendor}</th>
 527      *     <td>Java Virtual Machine specification vendor</td></tr>
 528      * <tr><th scope="row">{@systemProperty java.vm.specification.name}</th>
 529      *     <td>Java Virtual Machine specification name</td></tr>
 530      * <tr><th scope="row">{@systemProperty java.vm.version}</th>
 531      *     <td>Java Virtual Machine implementation version which may be
 532      *     interpreted as a {@link Runtime.Version}</td></tr>
 533      * <tr><th scope="row">{@systemProperty java.vm.vendor}</th>
 534      *     <td>Java Virtual Machine implementation vendor</td></tr>
 535      * <tr><th scope="row">{@systemProperty java.vm.name}</th>
 536      *     <td>Java Virtual Machine implementation name</td></tr>
 537      * <tr><th scope="row">{@systemProperty java.specification.version}</th>
 538      *     <td>Java Runtime Environment specification version, whose value is
 539      *     the {@linkplain Runtime.Version#feature feature} element of the
 540      *     {@linkplain Runtime#version() runtime version}</td></tr>
 541      * <tr><th scope="row">{@systemProperty java.specification.maintenance.version}</th>
 542      *     <td>Java Runtime Environment specification maintenance version,
 543      *     may be interpreted as a positive integer <em>(optional, see below)</em></td></tr>
 544      * <tr><th scope="row">{@systemProperty java.specification.vendor}</th>
 545      *     <td>Java Runtime Environment specification  vendor</td></tr>
 546      * <tr><th scope="row">{@systemProperty java.specification.name}</th>
 547      *     <td>Java Runtime Environment specification  name</td></tr>
 548      * <tr><th scope="row">{@systemProperty java.class.version}</th>
 549      *     <td>{@linkplain java.lang.reflect.ClassFileFormatVersion#latest() Latest}
 550      *     Java class file format version recognized by the Java runtime as {@code "MAJOR.MINOR"}
 551      *     where {@link java.lang.reflect.ClassFileFormatVersion#major() MAJOR} and {@code MINOR}
 552      *     are both formatted as decimal integers</td></tr>
 553      * <tr><th scope="row">{@systemProperty java.class.path}</th>
 554      *     <td>Java class path  (refer to
 555      *        {@link ClassLoader#getSystemClassLoader()} for details)</td></tr>
 556      * <tr><th scope="row">{@systemProperty java.library.path}</th>
 557      *     <td>List of paths to search when loading libraries</td></tr>
 558      * <tr><th scope="row">{@systemProperty java.io.tmpdir}</th>
 559      *     <td>Default temp file path</td></tr>
 560      * <tr><th scope="row">{@systemProperty os.name}</th>
 561      *     <td>Operating system name</td></tr>
 562      * <tr><th scope="row">{@systemProperty os.arch}</th>
 563      *     <td>Operating system architecture</td></tr>
 564      * <tr><th scope="row">{@systemProperty os.version}</th>
 565      *     <td>Operating system version</td></tr>
 566      * <tr><th scope="row">{@systemProperty file.separator}</th>
 567      *     <td>File separator ("/" on UNIX)</td></tr>
 568      * <tr><th scope="row">{@systemProperty path.separator}</th>
 569      *     <td>Path separator (":" on UNIX)</td></tr>
 570      * <tr><th scope="row">{@systemProperty line.separator}</th>
 571      *     <td>Line separator ("\n" on UNIX)</td></tr>
 572      * <tr><th scope="row">{@systemProperty user.name}</th>
 573      *     <td>User's account name</td></tr>
 574      * <tr><th scope="row">{@systemProperty user.home}</th>
 575      *     <td>User's home directory</td></tr>
 576      * <tr><th scope="row">{@systemProperty user.dir}</th>
 577      *     <td>User's current working directory</td></tr>
 578      * <tr><th scope="row">{@systemProperty native.encoding}</th>
 579      *     <td>Character encoding name derived from the host environment and/or
 580      *     the user's settings. Setting this system property has no effect.</td></tr>
 581      * <tr><th scope="row">{@systemProperty stdout.encoding}</th>
 582      *     <td>Character encoding name for {@link System#out System.out} and
 583      *     {@link System#console() System.console()}.
 584      *     The Java runtime can be started with the system property set to {@code UTF-8},
 585      *     starting it with the property set to another value leads to undefined behavior.
 586      * <tr><th scope="row">{@systemProperty stderr.encoding}</th>
 587      *     <td>Character encoding name for {@link System#err System.err}.
 588      *     The Java runtime can be started with the system property set to {@code UTF-8},
 589      *     starting it with the property set to another value leads to undefined behavior.
 590      * </tbody>
 591      * </table>
 592      * <p>
 593      * The {@code java.specification.maintenance.version} property is
 594      * defined if the specification implemented by this runtime at the
 595      * time of its construction had undergone a <a
 596      * href="https://jcp.org/en/procedures/jcp2#3.6.4">maintenance
 597      * release</a>. When defined, its value identifies that
 598      * maintenance release. To indicate the first maintenance release
 599      * this property will have the value {@code "1"}, to indicate the
 600      * second maintenance release this property will have the value
 601      * {@code "2"}, and so on.
 602      * <p>
 603      * Multiple paths in a system property value are separated by the path
 604      * separator character of the platform.
 605      * <p>
 606      * Additional locale-related system properties defined by the
 607      * {@link Locale##default_locale Default Locale} section in the {@code Locale}
 608      * class description may also be obtained with this method.
 609      *
 610      * @apiNote
 611      * <strong>Changing a standard system property may have unpredictable results
 612      * unless otherwise specified.</strong>
 613      * Property values may be cached during initialization or on first use.
 614      * Setting a standard property after initialization using {@link #getProperties()},
 615      * {@link #setProperties(Properties)}, {@link #setProperty(String, String)}, or
 616      * {@link #clearProperty(String)} may not have the desired effect.
 617      *
 618      * @implNote
 619      * In addition to the standard system properties, the system
 620      * properties may include the following keys:
 621      * <table class="striped">
 622      * <caption style="display:none">Shows property keys and associated values</caption>
 623      * <thead>
 624      * <tr><th scope="col">Key</th>
 625      *     <th scope="col">Description of Associated Value</th></tr>
 626      * </thead>
 627      * <tbody>
 628      * <tr><th scope="row">{@systemProperty jdk.module.path}</th>
 629      *     <td>The application module path</td></tr>
 630      * <tr><th scope="row">{@systemProperty jdk.module.upgrade.path}</th>
 631      *     <td>The upgrade module path</td></tr>
 632      * <tr><th scope="row">{@systemProperty jdk.module.main}</th>
 633      *     <td>The module name of the initial/main module</td></tr>
 634      * <tr><th scope="row">{@systemProperty jdk.module.main.class}</th>
 635      *     <td>The main class name of the initial module</td></tr>
 636      * <tr><th scope="row">{@systemProperty file.encoding}</th>
 637      *     <td>The name of the default charset, defaults to {@code UTF-8}.
 638      *     The property may be set on the command line to the value
 639      *     {@code UTF-8} or {@code COMPAT}. If set on the command line to
 640      *     the value {@code COMPAT} then the value is replaced with the
 641      *     value of the {@code native.encoding} property during startup.
 642      *     Setting the property to a value other than {@code UTF-8} or
 643      *     {@code COMPAT} leads to unspecified behavior.
 644      *     </td></tr>
 645      * </tbody>
 646      * </table>
 647      *
 648      * @return     the system properties
 649      * @see        #setProperties
 650      * @see        java.util.Properties
 651      */
 652     public static Properties getProperties() {
 653         return props;
 654     }
 655 
 656     /**
 657      * Returns the system-dependent line separator string.  It always
 658      * returns the same value - the initial value of the {@linkplain
 659      * #getProperty(String) system property} {@code line.separator}.
 660      *
 661      * <p>On UNIX systems, it returns {@code "\n"}; on Microsoft
 662      * Windows systems it returns {@code "\r\n"}.
 663      *
 664      * @return the system-dependent line separator string
 665      * @since 1.7
 666      */
 667     public static String lineSeparator() {
 668         return lineSeparator;
 669     }
 670 
 671     private static String lineSeparator;
 672 
 673     /**
 674      * Sets the system properties to the {@code Properties} argument.
 675      * <p>
 676      * The argument becomes the current set of system properties for use
 677      * by the {@link #getProperty(String)} method. If the argument is
 678      * {@code null}, then the current set of system properties is
 679      * forgotten.
 680      *
 681      * @apiNote
 682      * <strong>Changing a standard system property may have unpredictable results
 683      * unless otherwise specified</strong>.
 684      * See {@linkplain #getProperties getProperties} for details.
 685      *
 686      * @param      props   the new system properties.
 687      * @see        #getProperties
 688      * @see        java.util.Properties
 689      */
 690     public static void setProperties(Properties props) {
 691         if (props == null) {
 692             Map<String, String> tempProps = SystemProps.initProperties();
 693             VersionProps.init(tempProps);
 694             props = createProperties(tempProps);
 695         }
 696         System.props = props;
 697     }
 698 
 699     /**
 700      * Gets the system property indicated by the specified key.
 701      * <p>
 702      * If there is no current set of system properties, a set of system
 703      * properties is first created and initialized in the same manner as
 704      * for the {@code getProperties} method.
 705      *
 706      * @apiNote
 707      * <strong>Changing a standard system property may have unpredictable results
 708      * unless otherwise specified</strong>.
 709      * See {@linkplain #getProperties getProperties} for details.
 710      *
 711      * @param      key   the name of the system property.
 712      * @return     the string value of the system property,
 713      *             or {@code null} if there is no property with that key.
 714      *
 715      * @throws     NullPointerException if {@code key} is {@code null}.
 716      * @throws     IllegalArgumentException if {@code key} is empty.
 717      * @see        #setProperty
 718      * @see        java.lang.System#getProperties()
 719      */
 720     public static String getProperty(String key) {
 721         checkKey(key);
 722         return props.getProperty(key);
 723     }
 724 
 725     /**
 726      * Gets the system property indicated by the specified key.
 727      * <p>
 728      * If there is no current set of system properties, a set of system
 729      * properties is first created and initialized in the same manner as
 730      * for the {@code getProperties} method.
 731      *
 732      * @param      key   the name of the system property.
 733      * @param      def   a default value.
 734      * @return     the string value of the system property,
 735      *             or the default value if there is no property with that key.
 736      *
 737      * @throws     NullPointerException if {@code key} is {@code null}.
 738      * @throws     IllegalArgumentException if {@code key} is empty.
 739      * @see        #setProperty
 740      * @see        java.lang.System#getProperties()
 741      */
 742     public static String getProperty(String key, String def) {
 743         checkKey(key);
 744         return props.getProperty(key, def);
 745     }
 746 
 747     /**
 748      * Sets the system property indicated by the specified key.
 749      *
 750      * @apiNote
 751      * <strong>Changing a standard system property may have unpredictable results
 752      * unless otherwise specified</strong>.
 753      * See {@linkplain #getProperties getProperties} for details.
 754      *
 755      * @param      key   the name of the system property.
 756      * @param      value the value of the system property.
 757      * @return     the previous value of the system property,
 758      *             or {@code null} if it did not have one.
 759      *
 760      * @throws     NullPointerException if {@code key} or
 761      *             {@code value} is {@code null}.
 762      * @throws     IllegalArgumentException if {@code key} is empty.
 763      * @see        #getProperty
 764      * @see        java.lang.System#getProperty(java.lang.String)
 765      * @see        java.lang.System#getProperty(java.lang.String, java.lang.String)
 766      * @since      1.2
 767      */
 768     public static String setProperty(String key, String value) {
 769         checkKey(key);
 770         return (String) props.setProperty(key, value);
 771     }
 772 
 773     /**
 774      * Removes the system property indicated by the specified key.
 775      *
 776      * @apiNote
 777      * <strong>Changing a standard system property may have unpredictable results
 778      * unless otherwise specified</strong>.
 779      * See {@linkplain #getProperties getProperties} method for details.
 780      *
 781      * @param      key   the name of the system property to be removed.
 782      * @return     the previous string value of the system property,
 783      *             or {@code null} if there was no property with that key.
 784      *
 785      * @throws     NullPointerException if {@code key} is {@code null}.
 786      * @throws     IllegalArgumentException if {@code key} is empty.
 787      * @see        #getProperty
 788      * @see        #setProperty
 789      * @see        java.util.Properties
 790      * @since 1.5
 791      */
 792     public static String clearProperty(String key) {
 793         checkKey(key);
 794         return (String) props.remove(key);
 795     }
 796 
 797     private static void checkKey(String key) {
 798         if (key == null) {
 799             throw new NullPointerException("key can't be null");
 800         }
 801         if (key.isEmpty()) {
 802             throw new IllegalArgumentException("key can't be empty");
 803         }
 804     }
 805 
 806     /**
 807      * Gets the value of the specified environment variable. An
 808      * environment variable is a system-dependent external named
 809      * value.
 810      *
 811      * <p><a id="EnvironmentVSSystemProperties"><i>System
 812      * properties</i> and <i>environment variables</i></a> are both
 813      * conceptually mappings between names and values.  Both
 814      * mechanisms can be used to pass user-defined information to a
 815      * Java process.  Environment variables have a more global effect,
 816      * because they are visible to all descendants of the process
 817      * which defines them, not just the immediate Java subprocess.
 818      * They can have subtly different semantics, such as case
 819      * insensitivity, on different operating systems.  For these
 820      * reasons, environment variables are more likely to have
 821      * unintended side effects.  It is best to use system properties
 822      * where possible.  Environment variables should be used when a
 823      * global effect is desired, or when an external system interface
 824      * requires an environment variable (such as {@code PATH}).
 825      *
 826      * <p>On UNIX systems the alphabetic case of {@code name} is
 827      * typically significant, while on Microsoft Windows systems it is
 828      * typically not.  For example, the expression
 829      * {@code System.getenv("FOO").equals(System.getenv("foo"))}
 830      * is likely to be true on Microsoft Windows.
 831      *
 832      * @param  name the name of the environment variable
 833      * @return the string value of the variable, or {@code null}
 834      *         if the variable is not defined in the system environment
 835      * @throws NullPointerException if {@code name} is {@code null}
 836      * @see    #getenv()
 837      * @see    ProcessBuilder#environment()
 838      */
 839     public static String getenv(String name) {
 840         return ProcessEnvironment.getenv(name);
 841     }
 842 
 843 
 844     /**
 845      * Returns an unmodifiable string map view of the current system environment.
 846      * The environment is a system-dependent mapping from names to
 847      * values which is passed from parent to child processes.
 848      *
 849      * <p>If the system does not support environment variables, an
 850      * empty map is returned.
 851      *
 852      * <p>The returned map will never contain null keys or values.
 853      * Attempting to query the presence of a null key or value will
 854      * throw a {@link NullPointerException}.  Attempting to query
 855      * the presence of a key or value which is not of type
 856      * {@link String} will throw a {@link ClassCastException}.
 857      *
 858      * <p>The returned map and its collection views may not obey the
 859      * general contract of the {@link Object#equals} and
 860      * {@link Object#hashCode} methods.
 861      *
 862      * <p>The returned map is typically case-sensitive on all platforms.
 863      *
 864      * <p>When passing information to a Java subprocess,
 865      * <a href=#EnvironmentVSSystemProperties>system properties</a>
 866      * are generally preferred over environment variables.
 867      *
 868      * @return the environment as a map of variable names to values
 869      * @see    #getenv(String)
 870      * @see    ProcessBuilder#environment()
 871      * @since  1.5
 872      */
 873     public static java.util.Map<String,String> getenv() {
 874         return ProcessEnvironment.getenv();
 875     }
 876 
 877     /**
 878      * {@code System.Logger} instances log messages that will be
 879      * routed to the underlying logging framework the {@link System.LoggerFinder
 880      * LoggerFinder} uses.
 881      *
 882      * {@code System.Logger} instances are typically obtained from
 883      * the {@link java.lang.System System} class, by calling
 884      * {@link java.lang.System#getLogger(java.lang.String) System.getLogger(loggerName)}
 885      * or {@link java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle)
 886      * System.getLogger(loggerName, bundle)}.
 887      *
 888      * @see java.lang.System#getLogger(java.lang.String)
 889      * @see java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle)
 890      * @see java.lang.System.LoggerFinder
 891      *
 892      * @since 9
 893      */
 894     public interface Logger {
 895 
 896         /**
 897          * System {@linkplain Logger loggers} levels.
 898          *
 899          * A level has a {@linkplain #getName() name} and {@linkplain
 900          * #getSeverity() severity}.
 901          * Level values are {@link #ALL}, {@link #TRACE}, {@link #DEBUG},
 902          * {@link #INFO}, {@link #WARNING}, {@link #ERROR}, {@link #OFF},
 903          * by order of increasing severity.
 904          * <br>
 905          * {@link #ALL} and {@link #OFF}
 906          * are simple markers with severities mapped respectively to
 907          * {@link java.lang.Integer#MIN_VALUE Integer.MIN_VALUE} and
 908          * {@link java.lang.Integer#MAX_VALUE Integer.MAX_VALUE}.
 909          * <p>
 910          * <b>Severity values and Mapping to {@code java.util.logging.Level}.</b>
 911          * <p>
 912          * {@linkplain System.Logger.Level System logger levels} are mapped to
 913          * {@linkplain java.logging/java.util.logging.Level  java.util.logging levels}
 914          * of corresponding severity.
 915          * <br>The mapping is as follows:
 916          * <br><br>
 917          * <table class="striped">
 918          * <caption>System.Logger Severity Level Mapping</caption>
 919          * <thead>
 920          * <tr><th scope="col">System.Logger Levels</th>
 921          *     <th scope="col">java.util.logging Levels</th>
 922          * </thead>
 923          * <tbody>
 924          * <tr><th scope="row">{@link Logger.Level#ALL ALL}</th>
 925          *     <td>{@link java.logging/java.util.logging.Level#ALL ALL}</td>
 926          * <tr><th scope="row">{@link Logger.Level#TRACE TRACE}</th>
 927          *     <td>{@link java.logging/java.util.logging.Level#FINER FINER}</td>
 928          * <tr><th scope="row">{@link Logger.Level#DEBUG DEBUG}</th>
 929          *     <td>{@link java.logging/java.util.logging.Level#FINE FINE}</td>
 930          * <tr><th scope="row">{@link Logger.Level#INFO INFO}</th>
 931          *     <td>{@link java.logging/java.util.logging.Level#INFO INFO}</td>
 932          * <tr><th scope="row">{@link Logger.Level#WARNING WARNING}</th>
 933          *     <td>{@link java.logging/java.util.logging.Level#WARNING WARNING}</td>
 934          * <tr><th scope="row">{@link Logger.Level#ERROR ERROR}</th>
 935          *     <td>{@link java.logging/java.util.logging.Level#SEVERE SEVERE}</td>
 936          * <tr><th scope="row">{@link Logger.Level#OFF OFF}</th>
 937          *     <td>{@link java.logging/java.util.logging.Level#OFF OFF}</td>
 938          * </tbody>
 939          * </table>
 940          *
 941          * @since 9
 942          *
 943          * @see java.lang.System.LoggerFinder
 944          * @see java.lang.System.Logger
 945          */
 946         @SuppressWarnings("doclint:reference") // cross-module links
 947         public enum Level {
 948 
 949             // for convenience, we're reusing java.util.logging.Level int values
 950             // the mapping logic in sun.util.logging.PlatformLogger depends
 951             // on this.
 952             /**
 953              * A marker to indicate that all levels are enabled.
 954              * This level {@linkplain #getSeverity() severity} is
 955              * {@link Integer#MIN_VALUE}.
 956              */
 957             ALL(Integer.MIN_VALUE),  // typically mapped to/from j.u.l.Level.ALL
 958             /**
 959              * {@code TRACE} level: usually used to log diagnostic information.
 960              * This level {@linkplain #getSeverity() severity} is
 961              * {@code 400}.
 962              */
 963             TRACE(400),   // typically mapped to/from j.u.l.Level.FINER
 964             /**
 965              * {@code DEBUG} level: usually used to log debug information traces.
 966              * This level {@linkplain #getSeverity() severity} is
 967              * {@code 500}.
 968              */
 969             DEBUG(500),   // typically mapped to/from j.u.l.Level.FINEST/FINE/CONFIG
 970             /**
 971              * {@code INFO} level: usually used to log information messages.
 972              * This level {@linkplain #getSeverity() severity} is
 973              * {@code 800}.
 974              */
 975             INFO(800),    // typically mapped to/from j.u.l.Level.INFO
 976             /**
 977              * {@code WARNING} level: usually used to log warning messages.
 978              * This level {@linkplain #getSeverity() severity} is
 979              * {@code 900}.
 980              */
 981             WARNING(900), // typically mapped to/from j.u.l.Level.WARNING
 982             /**
 983              * {@code ERROR} level: usually used to log error messages.
 984              * This level {@linkplain #getSeverity() severity} is
 985              * {@code 1000}.
 986              */
 987             ERROR(1000),  // typically mapped to/from j.u.l.Level.SEVERE
 988             /**
 989              * A marker to indicate that all levels are disabled.
 990              * This level {@linkplain #getSeverity() severity} is
 991              * {@link Integer#MAX_VALUE}.
 992              */
 993             OFF(Integer.MAX_VALUE);  // typically mapped to/from j.u.l.Level.OFF
 994 
 995             private final int severity;
 996 
 997             private Level(int severity) {
 998                 this.severity = severity;
 999             }
1000 
1001             /**
1002              * Returns the name of this level.
1003              * @return this level {@linkplain #name()}.
1004              */
1005             public final String getName() {
1006                 return name();
1007             }
1008 
1009             /**
1010              * Returns the severity of this level.
1011              * A higher severity means a more severe condition.
1012              * @return this level severity.
1013              */
1014             public final int getSeverity() {
1015                 return severity;
1016             }
1017         }
1018 
1019         /**
1020          * Returns the name of this logger.
1021          *
1022          * @return the logger name.
1023          */
1024         public String getName();
1025 
1026         /**
1027          * Checks if a message of the given level would be logged by
1028          * this logger.
1029          *
1030          * @param level the log message level.
1031          * @return {@code true} if the given log message level is currently
1032          *         being logged.
1033          *
1034          * @throws NullPointerException if {@code level} is {@code null}.
1035          */
1036         public boolean isLoggable(Level level);
1037 
1038         /**
1039          * Logs a message.
1040          *
1041          * @implSpec The default implementation for this method calls
1042          * {@code this.log(level, (ResourceBundle)null, msg, (Object[])null);}
1043          *
1044          * @param level the log message level.
1045          * @param msg the string message (or a key in the message catalog, if
1046          * this logger is a {@link
1047          * LoggerFinder#getLocalizedLogger(java.lang.String,
1048          * java.util.ResourceBundle, java.lang.Module) localized logger});
1049          * can be {@code null}.
1050          *
1051          * @throws NullPointerException if {@code level} is {@code null}.
1052          */
1053         public default void log(Level level, String msg) {
1054             log(level, (ResourceBundle) null, msg, (Object[]) null);
1055         }
1056 
1057         /**
1058          * Logs a lazily supplied message.
1059          *
1060          * If the logger is currently enabled for the given log message level
1061          * then a message is logged that is the result produced by the
1062          * given supplier function.  Otherwise, the supplier is not operated on.
1063          *
1064          * @implSpec When logging is enabled for the given level, the default
1065          * implementation for this method calls
1066          * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), (Object[])null);}
1067          *
1068          * @param level the log message level.
1069          * @param msgSupplier a supplier function that produces a message.
1070          *
1071          * @throws NullPointerException if {@code level} is {@code null},
1072          *         or {@code msgSupplier} is {@code null}.
1073          */
1074         public default void log(Level level, Supplier<String> msgSupplier) {
1075             Objects.requireNonNull(msgSupplier);
1076             if (isLoggable(Objects.requireNonNull(level))) {
1077                 log(level, (ResourceBundle) null, msgSupplier.get(), (Object[]) null);
1078             }
1079         }
1080 
1081         /**
1082          * Logs a message produced from the given object.
1083          *
1084          * If the logger is currently enabled for the given log message level then
1085          * a message is logged that, by default, is the result produced from
1086          * calling  toString on the given object.
1087          * Otherwise, the object is not operated on.
1088          *
1089          * @implSpec When logging is enabled for the given level, the default
1090          * implementation for this method calls
1091          * {@code this.log(level, (ResourceBundle)null, obj.toString(), (Object[])null);}
1092          *
1093          * @param level the log message level.
1094          * @param obj the object to log.
1095          *
1096          * @throws NullPointerException if {@code level} is {@code null}, or
1097          *         {@code obj} is {@code null}.
1098          */
1099         public default void log(Level level, Object obj) {
1100             Objects.requireNonNull(obj);
1101             if (isLoggable(Objects.requireNonNull(level))) {
1102                 this.log(level, (ResourceBundle) null, obj.toString(), (Object[]) null);
1103             }
1104         }
1105 
1106         /**
1107          * Logs a message associated with a given throwable.
1108          *
1109          * @implSpec The default implementation for this method calls
1110          * {@code this.log(level, (ResourceBundle)null, msg, thrown);}
1111          *
1112          * @param level the log message level.
1113          * @param msg the string message (or a key in the message catalog, if
1114          * this logger is a {@link
1115          * LoggerFinder#getLocalizedLogger(java.lang.String,
1116          * java.util.ResourceBundle, java.lang.Module) localized logger});
1117          * can be {@code null}.
1118          * @param thrown a {@code Throwable} associated with the log message;
1119          *        can be {@code null}.
1120          *
1121          * @throws NullPointerException if {@code level} is {@code null}.
1122          */
1123         public default void log(Level level, String msg, Throwable thrown) {
1124             this.log(level, null, msg, thrown);
1125         }
1126 
1127         /**
1128          * Logs a lazily supplied message associated with a given throwable.
1129          *
1130          * If the logger is currently enabled for the given log message level
1131          * then a message is logged that is the result produced by the
1132          * given supplier function.  Otherwise, the supplier is not operated on.
1133          *
1134          * @implSpec When logging is enabled for the given level, the default
1135          * implementation for this method calls
1136          * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), thrown);}
1137          *
1138          * @param level one of the log message level identifiers.
1139          * @param msgSupplier a supplier function that produces a message.
1140          * @param thrown a {@code Throwable} associated with log message;
1141          *               can be {@code null}.
1142          *
1143          * @throws NullPointerException if {@code level} is {@code null}, or
1144          *                               {@code msgSupplier} is {@code null}.
1145          */
1146         public default void log(Level level, Supplier<String> msgSupplier,
1147                 Throwable thrown) {
1148             Objects.requireNonNull(msgSupplier);
1149             if (isLoggable(Objects.requireNonNull(level))) {
1150                 this.log(level, null, msgSupplier.get(), thrown);
1151             }
1152         }
1153 
1154         /**
1155          * Logs a message with an optional list of parameters.
1156          *
1157          * @implSpec The default implementation for this method calls
1158          * {@code this.log(level, (ResourceBundle)null, format, params);}
1159          *
1160          * @param level one of the log message level identifiers.
1161          * @param format the string message format in {@link
1162          * java.text.MessageFormat} format, (or a key in the message
1163          * catalog, if this logger is a {@link
1164          * LoggerFinder#getLocalizedLogger(java.lang.String,
1165          * java.util.ResourceBundle, java.lang.Module) localized logger});
1166          * can be {@code null}.
1167          * @param params an optional list of parameters to the message (may be
1168          * none).
1169          *
1170          * @throws NullPointerException if {@code level} is {@code null}.
1171          */
1172         public default void log(Level level, String format, Object... params) {
1173             this.log(level, null, format, params);
1174         }
1175 
1176         /**
1177          * Logs a localized message associated with a given throwable.
1178          *
1179          * If the given resource bundle is non-{@code null},  the {@code msg}
1180          * string is localized using the given resource bundle.
1181          * Otherwise the {@code msg} string is not localized.
1182          *
1183          * @param level the log message level.
1184          * @param bundle a resource bundle to localize {@code msg}; can be
1185          * {@code null}.
1186          * @param msg the string message (or a key in the message catalog,
1187          *            if {@code bundle} is not {@code null}); can be {@code null}.
1188          * @param thrown a {@code Throwable} associated with the log message;
1189          *        can be {@code null}.
1190          *
1191          * @throws NullPointerException if {@code level} is {@code null}.
1192          */
1193         public void log(Level level, ResourceBundle bundle, String msg,
1194                 Throwable thrown);
1195 
1196         /**
1197          * Logs a message with resource bundle and an optional list of
1198          * parameters.
1199          *
1200          * If the given resource bundle is non-{@code null},  the {@code format}
1201          * string is localized using the given resource bundle.
1202          * Otherwise the {@code format} string is not localized.
1203          *
1204          * @param level the log message level.
1205          * @param bundle a resource bundle to localize {@code format}; can be
1206          * {@code null}.
1207          * @param format the string message format in {@link
1208          * java.text.MessageFormat} format, (or a key in the message
1209          * catalog if {@code bundle} is not {@code null}); can be {@code null}.
1210          * @param params an optional list of parameters to the message (may be
1211          * none).
1212          *
1213          * @throws NullPointerException if {@code level} is {@code null}.
1214          */
1215         public void log(Level level, ResourceBundle bundle, String format,
1216                 Object... params);
1217     }
1218 
1219     /**
1220      * The {@code LoggerFinder} service is responsible for creating, managing,
1221      * and configuring loggers to the underlying framework it uses.
1222      *
1223      * A logger finder is a concrete implementation of this class that has a
1224      * zero-argument constructor and implements the abstract methods defined
1225      * by this class.
1226      * The loggers returned from a logger finder are capable of routing log
1227      * messages to the logging backend this provider supports.
1228      * A given invocation of the Java Runtime maintains a single
1229      * system-wide LoggerFinder instance that is loaded as follows:
1230      * <ul>
1231      *    <li>First it finds any custom {@code LoggerFinder} provider
1232      *        using the {@link java.util.ServiceLoader} facility with the
1233      *        {@linkplain ClassLoader#getSystemClassLoader() system class
1234      *        loader}.</li>
1235      *    <li>If no {@code LoggerFinder} provider is found, the system default
1236      *        {@code LoggerFinder} implementation will be used.</li>
1237      * </ul>
1238      * <p>
1239      * An application can replace the logging backend
1240      * <i>even when the java.logging module is present</i>, by simply providing
1241      * and declaring an implementation of the {@link LoggerFinder} service.
1242      * <p>
1243      * <b>Default Implementation</b>
1244      * <p>
1245      * The system default {@code LoggerFinder} implementation uses
1246      * {@code java.util.logging} as the backend framework when the
1247      * {@code java.logging} module is present.
1248      * It returns a {@linkplain System.Logger logger} instance
1249      * that will route log messages to a {@link java.logging/java.util.logging.Logger
1250      * java.util.logging.Logger}. Otherwise, if {@code java.logging} is not
1251      * present, the default implementation will return a simple logger
1252      * instance that will route log messages of {@code INFO} level and above to
1253      * the console ({@code System.err}).
1254      * <p>
1255      * <b>Logging Configuration</b>
1256      * <p>
1257      * {@linkplain Logger Logger} instances obtained from the
1258      * {@code LoggerFinder} factory methods are not directly configurable by
1259      * the application. Configuration is the responsibility of the underlying
1260      * logging backend, and usually requires using APIs specific to that backend.
1261      * <p>For the default {@code LoggerFinder} implementation
1262      * using {@code java.util.logging} as its backend, refer to
1263      * {@link java.logging/java.util.logging java.util.logging} for logging configuration.
1264      * For the default {@code LoggerFinder} implementation returning simple loggers
1265      * when the {@code java.logging} module is absent, the configuration
1266      * is implementation dependent.
1267      * <p>
1268      * Usually an application that uses a logging framework will log messages
1269      * through a logger facade defined (or supported) by that framework.
1270      * Applications that wish to use an external framework should log
1271      * through the facade associated with that framework.
1272      * <p>
1273      * A system class that needs to log messages will typically obtain
1274      * a {@link System.Logger} instance to route messages to the logging
1275      * framework selected by the application.
1276      * <p>
1277      * Libraries and classes that only need loggers to produce log messages
1278      * should not attempt to configure loggers by themselves, as that
1279      * would make them dependent from a specific implementation of the
1280      * {@code LoggerFinder} service.
1281      * <p>
1282      * <b>Message Levels and Mapping to backend levels</b>
1283      * <p>
1284      * A logger finder is responsible for mapping from a {@code
1285      * System.Logger.Level} to a level supported by the logging backend it uses.
1286      * <br>The default LoggerFinder using {@code java.util.logging} as the backend
1287      * maps {@code System.Logger} levels to
1288      * {@linkplain java.logging/java.util.logging.Level java.util.logging} levels
1289      * of corresponding severity - as described in {@link Logger.Level
1290      * Logger.Level}.
1291      *
1292      * @see java.lang.System
1293      * @see java.lang.System.Logger
1294      *
1295      * @since 9
1296      */
1297     @SuppressWarnings("doclint:reference") // cross-module links
1298     public abstract static class LoggerFinder {
1299 
1300         /**
1301          * Creates a new instance of {@code LoggerFinder}.
1302          *
1303          * @implNote It is recommended that a {@code LoggerFinder} service
1304          *   implementation does not perform any heavy initialization in its
1305          *   constructor, in order to avoid possible risks of deadlock or class
1306          *   loading cycles during the instantiation of the service provider.
1307          */
1308         protected LoggerFinder() {
1309         }
1310 
1311         /**
1312          * Returns an instance of {@link Logger Logger}
1313          * for the given {@code module}.
1314          *
1315          * @param name the name of the logger.
1316          * @param module the module for which the logger is being requested.
1317          *
1318          * @return a {@link Logger logger} suitable for use within the given
1319          *         module.
1320          * @throws NullPointerException if {@code name} is {@code null} or
1321          *        {@code module} is {@code null}.
1322          */
1323         public abstract Logger getLogger(String name, Module module);
1324 
1325         /**
1326          * Returns a localizable instance of {@link Logger Logger}
1327          * for the given {@code module}.
1328          * The returned logger will use the provided resource bundle for
1329          * message localization.
1330          *
1331          * @implSpec By default, this method calls {@link
1332          * #getLogger(java.lang.String, java.lang.Module)
1333          * this.getLogger(name, module)} to obtain a logger, then wraps that
1334          * logger in a {@link Logger} instance where all methods that do not
1335          * take a {@link ResourceBundle} as parameter are redirected to one
1336          * which does - passing the given {@code bundle} for
1337          * localization. So for instance, a call to {@link
1338          * Logger#log(Logger.Level, String) Logger.log(Level.INFO, msg)}
1339          * will end up as a call to {@link
1340          * Logger#log(Logger.Level, ResourceBundle, String, Object...)
1341          * Logger.log(Level.INFO, bundle, msg, (Object[])null)} on the wrapped
1342          * logger instance.
1343          * Note however that by default, string messages returned by {@link
1344          * java.util.function.Supplier Supplier&lt;String&gt;} will not be
1345          * localized, as it is assumed that such strings are messages which are
1346          * already constructed, rather than keys in a resource bundle.
1347          * <p>
1348          * An implementation of {@code LoggerFinder} may override this method,
1349          * for example, when the underlying logging backend provides its own
1350          * mechanism for localizing log messages, then such a
1351          * {@code LoggerFinder} would be free to return a logger
1352          * that makes direct use of the mechanism provided by the backend.
1353          *
1354          * @param name    the name of the logger.
1355          * @param bundle  a resource bundle; can be {@code null}.
1356          * @param module  the module for which the logger is being requested.
1357          * @return an instance of {@link Logger Logger}  which will use the
1358          * provided resource bundle for message localization.
1359          *
1360          * @throws NullPointerException if {@code name} is {@code null} or
1361          *         {@code module} is {@code null}.
1362          */
1363         public Logger getLocalizedLogger(String name, ResourceBundle bundle,
1364                                          Module module) {
1365             return new LocalizedLoggerWrapper<>(getLogger(name, module), bundle);
1366         }
1367 
1368         /**
1369          * Returns the {@code LoggerFinder} instance. There is one
1370          * single system-wide {@code LoggerFinder} instance in
1371          * the Java Runtime.  See the class specification of how the
1372          * {@link LoggerFinder LoggerFinder} implementation is located and
1373          * loaded.
1374          *
1375          * @return the {@link LoggerFinder LoggerFinder} instance.
1376          */
1377         public static LoggerFinder getLoggerFinder() {
1378             return accessProvider();
1379         }
1380 
1381 
1382         private static volatile LoggerFinder service;
1383         static LoggerFinder accessProvider() {
1384             // We do not need to synchronize: LoggerFinderLoader will
1385             // always return the same instance, so if we don't have it,
1386             // just fetch it again.
1387             LoggerFinder finder = service;
1388             if (finder == null) {
1389                 finder = LoggerFinderLoader.getLoggerFinder();
1390                 if (finder instanceof TemporaryLoggerFinder) return finder;
1391                 service = finder;
1392             }
1393             return finder;
1394         }
1395 
1396     }
1397 
1398 
1399     /**
1400      * Returns an instance of {@link Logger Logger} for the caller's
1401      * use.
1402      *
1403      * @implSpec
1404      * Instances returned by this method route messages to loggers
1405      * obtained by calling {@link LoggerFinder#getLogger(java.lang.String,
1406      * java.lang.Module) LoggerFinder.getLogger(name, module)}, where
1407      * {@code module} is the caller's module.
1408      * In cases where {@code System.getLogger} is called from a context where
1409      * there is no caller frame on the stack (e.g when called directly
1410      * from a JNI attached thread), {@code IllegalCallerException} is thrown.
1411      * To obtain a logger in such a context, use an auxiliary class that will
1412      * implicitly be identified as the caller, or use the system {@link
1413      * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead.
1414      * Note that doing the latter may eagerly initialize the underlying
1415      * logging system.
1416      *
1417      * @apiNote
1418      * This method may defer calling the {@link
1419      * LoggerFinder#getLogger(java.lang.String, java.lang.Module)
1420      * LoggerFinder.getLogger} method to create an actual logger supplied by
1421      * the logging backend, for instance, to allow loggers to be obtained during
1422      * the system initialization time.
1423      *
1424      * @param name the name of the logger.
1425      * @return an instance of {@link Logger} that can be used by the calling
1426      *         class.
1427      * @throws NullPointerException if {@code name} is {@code null}.
1428      * @throws IllegalCallerException if there is no Java caller frame on the
1429      *         stack.
1430      *
1431      * @since 9
1432      */
1433     @CallerSensitive
1434     public static Logger getLogger(String name) {
1435         Objects.requireNonNull(name);
1436         final Class<?> caller = Reflection.getCallerClass();
1437         if (caller == null) {
1438             throw new IllegalCallerException("no caller frame");
1439         }
1440         return LazyLoggers.getLogger(name, caller.getModule());
1441     }
1442 
1443     /**
1444      * Returns a localizable instance of {@link Logger
1445      * Logger} for the caller's use.
1446      * The returned logger will use the provided resource bundle for message
1447      * localization.
1448      *
1449      * @implSpec
1450      * The returned logger will perform message localization as specified
1451      * by {@link LoggerFinder#getLocalizedLogger(java.lang.String,
1452      * java.util.ResourceBundle, java.lang.Module)
1453      * LoggerFinder.getLocalizedLogger(name, bundle, module)}, where
1454      * {@code module} is the caller's module.
1455      * In cases where {@code System.getLogger} is called from a context where
1456      * there is no caller frame on the stack (e.g when called directly
1457      * from a JNI attached thread), {@code IllegalCallerException} is thrown.
1458      * To obtain a logger in such a context, use an auxiliary class that
1459      * will implicitly be identified as the caller, or use the system {@link
1460      * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead.
1461      * Note that doing the latter may eagerly initialize the underlying
1462      * logging system.
1463      *
1464      * @apiNote
1465      * This method is intended to be used after the system is fully initialized.
1466      * This method may trigger the immediate loading and initialization
1467      * of the {@link LoggerFinder} service, which may cause issues if the
1468      * Java Runtime is not ready to initialize the concrete service
1469      * implementation yet.
1470      * System classes which may be loaded early in the boot sequence and
1471      * need to log localized messages should create a logger using
1472      * {@link #getLogger(java.lang.String)} and then use the log methods that
1473      * take a resource bundle as parameter.
1474      *
1475      * @param name    the name of the logger.
1476      * @param bundle  a resource bundle.
1477      * @return an instance of {@link Logger} which will use the provided
1478      * resource bundle for message localization.
1479      * @throws NullPointerException if {@code name} is {@code null} or
1480      *         {@code bundle} is {@code null}.
1481      * @throws IllegalCallerException if there is no Java caller frame on the
1482      *         stack.
1483      *
1484      * @since 9
1485      */
1486     @CallerSensitive
1487     public static Logger getLogger(String name, ResourceBundle bundle) {
1488         final ResourceBundle rb = Objects.requireNonNull(bundle);
1489         Objects.requireNonNull(name);
1490         final Class<?> caller = Reflection.getCallerClass();
1491         if (caller == null) {
1492             throw new IllegalCallerException("no caller frame");
1493         }
1494         return LoggerFinder.accessProvider()
1495                 .getLocalizedLogger(name, rb, caller.getModule());
1496     }
1497 
1498     /**
1499      * Initiates the {@linkplain Runtime##shutdown shutdown sequence} of the Java Virtual
1500      * Machine. This method initiates the shutdown sequence (if it is not already initiated)
1501      * and then blocks indefinitely. This method neither returns nor throws an exception;
1502      * that is, it does not complete either normally or abruptly.
1503      * <p>
1504      * The argument serves as a status code. By convention, a nonzero status code
1505      * indicates abnormal termination.
1506      * <p>
1507      * The call {@code System.exit(n)} is effectively equivalent to the call:
1508      * {@snippet :
1509      *     Runtime.getRuntime().exit(n)
1510      * }
1511      *
1512      * @implNote
1513      * The initiation of the shutdown sequence is logged by {@link Runtime#exit(int)}.
1514      *
1515      * @param  status exit status.
1516      * @see    java.lang.Runtime#exit(int)
1517      */
1518     public static void exit(int status) {
1519         Runtime.getRuntime().exit(status);
1520     }
1521 
1522     /**
1523      * Runs the garbage collector in the Java Virtual Machine.
1524      * <p>
1525      * Calling the {@code gc} method suggests that the Java Virtual Machine
1526      * expend effort toward recycling unused objects in order to
1527      * make the memory they currently occupy available for reuse
1528      * by the Java Virtual Machine.
1529      * When control returns from the method call, the Java Virtual Machine
1530      * has made a best effort to reclaim space from all unused objects.
1531      * There is no guarantee that this effort will recycle any particular
1532      * number of unused objects, reclaim any particular amount of space, or
1533      * complete at any particular time, if at all, before the method returns or ever.
1534      * There is also no guarantee that this effort will determine
1535      * the change of reachability in any particular number of objects,
1536      * or that any particular number of {@link java.lang.ref.Reference Reference}
1537      * objects will be cleared and enqueued.
1538      *
1539      * <p>
1540      * The call {@code System.gc()} is effectively equivalent to the
1541      * call:
1542      * <blockquote><pre>
1543      * Runtime.getRuntime().gc()
1544      * </pre></blockquote>
1545      *
1546      * @see     java.lang.Runtime#gc()
1547      */
1548     public static void gc() {
1549         Runtime.getRuntime().gc();
1550     }
1551 
1552     /**
1553      * Runs the finalization methods of any objects pending finalization.
1554      *
1555      * Calling this method suggests that the Java Virtual Machine expend
1556      * effort toward running the {@code finalize} methods of objects
1557      * that have been found to be discarded but whose {@code finalize}
1558      * methods have not yet been run. When control returns from the
1559      * method call, the Java Virtual Machine has made a best effort to
1560      * complete all outstanding finalizations.
1561      * <p>
1562      * The call {@code System.runFinalization()} is effectively
1563      * equivalent to the call:
1564      * <blockquote><pre>
1565      * Runtime.getRuntime().runFinalization()
1566      * </pre></blockquote>
1567      *
1568      * @deprecated Finalization has been deprecated for removal.  See
1569      * {@link java.lang.Object#finalize} for background information and details
1570      * about migration options.
1571      * <p>
1572      * When running in a JVM in which finalization has been disabled or removed,
1573      * no objects will be pending finalization, so this method does nothing.
1574      *
1575      * @see     java.lang.Runtime#runFinalization()
1576      * @jls 12.6 Finalization of Class Instances
1577      */
1578     @Deprecated(since="18", forRemoval=true)
1579     @SuppressWarnings("removal")
1580     public static void runFinalization() {
1581         Runtime.getRuntime().runFinalization();
1582     }
1583 
1584     /**
1585      * Loads the native library specified by the filename argument.  The filename
1586      * argument must be an absolute path name.
1587      *
1588      * If the filename argument, when stripped of any platform-specific library
1589      * prefix, path, and file extension, indicates a library whose name is,
1590      * for example, L, and a native library called L is statically linked
1591      * with the VM, then the JNI_OnLoad_L function exported by the library
1592      * is invoked rather than attempting to load a dynamic library.
1593      * A filename matching the argument does not have to exist in the
1594      * file system.
1595      * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>
1596      * for more details.
1597      *
1598      * Otherwise, the filename argument is mapped to a native library image in
1599      * an implementation-dependent manner.
1600      *
1601      * <p>
1602      * The call {@code System.load(name)} is effectively equivalent
1603      * to the call:
1604      * <blockquote><pre>
1605      * Runtime.getRuntime().load(name)
1606      * </pre></blockquote>
1607      *
1608      * @param      filename   the file to load.
1609      * @throws     UnsatisfiedLinkError  if either the filename is not an
1610      *             absolute path name, the native library is not statically
1611      *             linked with the VM, or the library cannot be mapped to
1612      *             a native library image by the host system.
1613      * @throws     NullPointerException if {@code filename} is {@code null}
1614      * @throws     IllegalCallerException if the caller is in a module that
1615      *             does not have native access enabled.
1616      *
1617      * @spec jni/index.html Java Native Interface Specification
1618      * @see        java.lang.Runtime#load(java.lang.String)
1619      */
1620     @CallerSensitive
1621     @Restricted
1622     public static void load(String filename) {
1623         Class<?> caller = Reflection.getCallerClass();
1624         Reflection.ensureNativeAccess(caller, System.class, "load", false);
1625         Runtime.getRuntime().load0(caller, filename);
1626     }
1627 
1628     /**
1629      * Loads the native library specified by the {@code libname}
1630      * argument.  The {@code libname} argument must not contain any platform
1631      * specific prefix, file extension or path. If a native library
1632      * called {@code libname} is statically linked with the VM, then the
1633      * JNI_OnLoad_{@code libname} function exported by the library is invoked.
1634      * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>
1635      * for more details.
1636      *
1637      * Otherwise, the libname argument is loaded from a system library
1638      * location and mapped to a native library image in an
1639      * implementation-dependent manner.
1640      * <p>
1641      * The call {@code System.loadLibrary(name)} is effectively
1642      * equivalent to the call
1643      * <blockquote><pre>
1644      * Runtime.getRuntime().loadLibrary(name)
1645      * </pre></blockquote>
1646      *
1647      * @param      libname   the name of the library.
1648      * @throws     UnsatisfiedLinkError if either the libname argument
1649      *             contains a file path, the native library is not statically
1650      *             linked with the VM,  or the library cannot be mapped to a
1651      *             native library image by the host system.
1652      * @throws     NullPointerException if {@code libname} is {@code null}
1653      * @throws     IllegalCallerException if the caller is in a module that
1654      *             does not have native access enabled.
1655      *
1656      * @spec jni/index.html Java Native Interface Specification
1657      * @see        java.lang.Runtime#loadLibrary(java.lang.String)
1658      */
1659     @CallerSensitive
1660     @Restricted
1661     public static void loadLibrary(String libname) {
1662         Class<?> caller = Reflection.getCallerClass();
1663         Reflection.ensureNativeAccess(caller, System.class, "loadLibrary", false);
1664         Runtime.getRuntime().loadLibrary0(caller, libname);
1665     }
1666 
1667     /**
1668      * Maps a library name into a platform-specific string representing
1669      * a native library.
1670      *
1671      * @param      libname the name of the library.
1672      * @return     a platform-dependent native library name.
1673      * @throws     NullPointerException if {@code libname} is {@code null}
1674      * @see        java.lang.System#loadLibrary(java.lang.String)
1675      * @see        java.lang.ClassLoader#findLibrary(java.lang.String)
1676      * @since      1.2
1677      */
1678     public static native String mapLibraryName(String libname);
1679 
1680     /**
1681      * Create PrintStream for stdout/err based on encoding.
1682      */
1683     private static PrintStream newPrintStream(OutputStream out, String enc) {
1684         if (enc != null) {
1685             return new PrintStream(new BufferedOutputStream(out, 128), true,
1686                                    Charset.forName(enc, UTF_8.INSTANCE));
1687         }
1688         return new PrintStream(new BufferedOutputStream(out, 128), true);
1689     }
1690 
1691     /**
1692      * Logs an exception/error at initialization time to stdout or stderr.
1693      *
1694      * @param printToStderr to print to stderr rather than stdout
1695      * @param printStackTrace to print the stack trace
1696      * @param msg the message to print before the exception, can be {@code null}
1697      * @param e the exception or error
1698      */
1699     private static void logInitException(boolean printToStderr,
1700                                          boolean printStackTrace,
1701                                          String msg,
1702                                          Throwable e) {
1703         if (VM.initLevel() < 1) {
1704             throw new InternalError("system classes not initialized");
1705         }
1706         PrintStream log = (printToStderr) ? err : out;
1707         if (msg != null) {
1708             log.println(msg);
1709         }
1710         if (printStackTrace) {
1711             e.printStackTrace(log);
1712         } else {
1713             log.println(e);
1714             for (Throwable suppressed : e.getSuppressed()) {
1715                 log.println("Suppressed: " + suppressed);
1716             }
1717             Throwable cause = e.getCause();
1718             if (cause != null) {
1719                 log.println("Caused by: " + cause);
1720             }
1721         }
1722     }
1723 
1724     /**
1725      * Create the Properties object from a map - masking out system properties
1726      * that are not intended for public access.
1727      */
1728     private static Properties createProperties(Map<String, String> initialProps) {
1729         Properties properties = new Properties(initialProps.size());
1730         for (var entry : initialProps.entrySet()) {
1731             String prop = entry.getKey();
1732             switch (prop) {
1733                 // Do not add private system properties to the Properties
1734                 case "sun.nio.MaxDirectMemorySize":
1735                 case "sun.nio.PageAlignDirectMemory":
1736                     // used by java.lang.Integer.IntegerCache
1737                 case "java.lang.Integer.IntegerCache.high":
1738                     // used by sun.launcher.LauncherHelper
1739                 case "sun.java.launcher.diag":
1740                     // used by jdk.internal.loader.ClassLoaders
1741                 case "jdk.boot.class.path.append":
1742                     break;
1743                 default:
1744                     properties.put(prop, entry.getValue());
1745             }
1746         }
1747         return properties;
1748     }
1749 
1750     /**
1751      * Initialize the system class.  Called after thread initialization.
1752      */
1753     private static void initPhase1() {
1754 
1755         // register the shared secrets - do this first, since SystemProps.initProperties
1756         // might initialize CharsetDecoders that rely on it
1757         setJavaLangAccess();
1758 
1759         // VM might invoke JNU_NewStringPlatform() to set those encoding
1760         // sensitive properties (user.home, user.name, boot.class.path, etc.)
1761         // during "props" initialization.
1762         // The charset is initialized in System.c and does not depend on the Properties.
1763         Map<String, String> tempProps = SystemProps.initProperties();
1764         VersionProps.init(tempProps);
1765 
1766         // There are certain system configurations that may be controlled by
1767         // VM options such as the maximum amount of direct memory and
1768         // Integer cache size used to support the object identity semantics
1769         // of autoboxing.  Typically, the library will obtain these values
1770         // from the properties set by the VM.  If the properties are for
1771         // internal implementation use only, these properties should be
1772         // masked from the system properties.
1773         //
1774         // Save a private copy of the system properties object that
1775         // can only be accessed by the internal implementation.
1776         VM.saveProperties(tempProps);
1777         props = createProperties(tempProps);
1778 
1779         // Check if sun.jnu.encoding is supported. If not, replace it with UTF-8.
1780         var jnuEncoding = props.getProperty("sun.jnu.encoding");
1781         if (jnuEncoding == null || !Charset.isSupported(jnuEncoding)) {
1782             notSupportedJnuEncoding = jnuEncoding == null ? "null" : jnuEncoding;
1783             props.setProperty("sun.jnu.encoding", "UTF-8");
1784         }
1785 
1786         StaticProperty.javaHome();          // Load StaticProperty to cache the property values
1787 
1788         lineSeparator = props.getProperty("line.separator");
1789 
1790         FileInputStream fdIn = new In(FileDescriptor.in);
1791         FileOutputStream fdOut = new Out(FileDescriptor.out);
1792         FileOutputStream fdErr = new Out(FileDescriptor.err);
1793         initialIn = new BufferedInputStream(fdIn);
1794         setIn0(initialIn);
1795         // stdout/err.encoding are set when the VM is associated with the terminal,
1796         // thus they are equivalent to Console.charset(), otherwise the encodings
1797         // of those properties default to native.encoding
1798         setOut0(newPrintStream(fdOut, props.getProperty("stdout.encoding")));
1799         initialErr = newPrintStream(fdErr, props.getProperty("stderr.encoding"));
1800         setErr0(initialErr);
1801 
1802         // Setup Java signal handlers for HUP, TERM, and INT (where available).
1803         Terminator.setup();
1804 
1805         // Initialize any miscellaneous operating system settings that need to be
1806         // set for the class libraries. Currently this is no-op everywhere except
1807         // for Windows where the process-wide error mode is set before the java.io
1808         // classes are used.
1809         VM.initializeOSEnvironment();
1810 
1811         // start Finalizer and Reference Handler threads
1812         SharedSecrets.getJavaLangRefAccess().startThreads();
1813 
1814         // system properties, java.lang and other core classes are now initialized
1815         VM.initLevel(1);
1816     }
1817 
1818     /**
1819      * System.in.
1820      */
1821     private static class In extends FileInputStream {
1822         In(FileDescriptor fd) {
1823             super(fd);
1824         }
1825 
1826         @Override
1827         public int read() throws IOException {
1828             boolean attempted = Blocker.begin();
1829             try {
1830                 return super.read();
1831             } finally {
1832                 Blocker.end(attempted);
1833             }
1834         }
1835 
1836         @Override
1837         public int read(byte[] b) throws IOException {
1838             boolean attempted = Blocker.begin();
1839             try {
1840                 return super.read(b);
1841             } finally {
1842                 Blocker.end(attempted);
1843             }
1844         }
1845 
1846         @Override
1847         public int read(byte[] b, int off, int len) throws IOException {
1848             boolean attempted = Blocker.begin();
1849             try {
1850                 return super.read(b, off, len);
1851             } finally {
1852                 Blocker.end(attempted);
1853             }
1854         }
1855     }
1856 
1857     /**
1858      * System.out/System.err wrap this output stream.
1859      */
1860     private static class Out extends FileOutputStream {
1861         Out(FileDescriptor fd) {
1862             super(fd);
1863         }
1864 
1865         @Override
1866         public void write(int b) throws IOException {
1867             boolean attempted = Blocker.begin();
1868             try {
1869                 super.write(b);
1870             } finally {
1871                 Blocker.end(attempted);
1872             }
1873         }
1874 
1875         @Override
1876         public void write(byte[] b) throws IOException {
1877             boolean attempted = Blocker.begin();
1878             try {
1879                 super.write(b);
1880             } finally {
1881                 Blocker.end(attempted);
1882             }
1883         }
1884 
1885         @Override
1886         public void write(byte[] b, int off, int len) throws IOException {
1887             boolean attempted = Blocker.begin();
1888             try {
1889                 super.write(b, off, len);
1890             } finally {
1891                 Blocker.end(attempted);
1892             }
1893         }
1894     }
1895 
1896     // @see #initPhase2()
1897     static ModuleLayer bootLayer;
1898 
1899     /*
1900      * Invoked by VM.  Phase 2 module system initialization.
1901      * Only classes in java.base can be loaded in this phase.
1902      *
1903      * @param printToStderr print exceptions to stderr rather than stdout
1904      * @param printStackTrace print stack trace when exception occurs
1905      *
1906      * @return JNI_OK for success, JNI_ERR for failure
1907      */
1908     private static int initPhase2(boolean printToStderr, boolean printStackTrace) {
1909 
1910         try {
1911             bootLayer = ModuleBootstrap.boot();
1912         } catch (Exception | Error e) {
1913             logInitException(printToStderr, printStackTrace,
1914                              "Error occurred during initialization of boot layer", e);
1915             return -1; // JNI_ERR
1916         }
1917 
1918         // module system initialized
1919         VM.initLevel(2);
1920 
1921         return 0; // JNI_OK
1922     }
1923 
1924     /*
1925      * Invoked by VM.  Phase 3 is the final system initialization:
1926      * 1. set system class loader
1927      * 2. set TCCL
1928      *
1929      * This method must be called after the module system initialization.
1930      */
1931     private static void initPhase3() {
1932 
1933         // Emit a warning if java.io.tmpdir is set via the command line
1934         // to a directory that doesn't exist
1935         if (SystemProps.isBadIoTmpdir()) {
1936             System.err.println("WARNING: java.io.tmpdir directory does not exist");
1937         }
1938 
1939         String smProp = System.getProperty("java.security.manager");
1940         if (smProp != null) {
1941             switch (smProp) {
1942                 case "disallow":
1943                     break;
1944                 case "allow":
1945                 case "":
1946                 case "default":
1947                 default:
1948                     throw new Error("A command line option has attempted to allow or enable the Security Manager."
1949                             + " Enabling a Security Manager is not supported.");
1950             }
1951         }
1952 
1953         // Emit a warning if `sun.jnu.encoding` is not supported.
1954         if (notSupportedJnuEncoding != null) {
1955             System.err.println(
1956                     "WARNING: The encoding of the underlying platform's" +
1957                     " file system is not supported: " +
1958                     notSupportedJnuEncoding);
1959         }
1960 
1961         // initializing the system class loader
1962         VM.initLevel(3);
1963 
1964         // system class loader initialized
1965         ClassLoader scl = ClassLoader.initSystemClassLoader();
1966 
1967         // set TCCL
1968         Thread.currentThread().setContextClassLoader(scl);
1969 
1970         // system is fully initialized
1971         VM.initLevel(4);
1972     }
1973 
1974     private static void setJavaLangAccess() {
1975         // Allow privileged classes outside of java.lang
1976         SharedSecrets.setJavaLangAccess(new JavaLangAccess() {
1977             public List<Method> getDeclaredPublicMethods(Class<?> klass, String name, Class<?>... parameterTypes) {
1978                 return klass.getDeclaredPublicMethods(name, parameterTypes);
1979             }
1980             public Method findMethod(Class<?> klass, boolean publicOnly, String name, Class<?>... parameterTypes) {
1981                 return klass.findMethod(publicOnly, name, parameterTypes);
1982             }
1983             public jdk.internal.reflect.ConstantPool getConstantPool(Class<?> klass) {
1984                 return klass.getConstantPool();
1985             }
1986             public boolean casAnnotationType(Class<?> klass, AnnotationType oldType, AnnotationType newType) {
1987                 return klass.casAnnotationType(oldType, newType);
1988             }
1989             public AnnotationType getAnnotationType(Class<?> klass) {
1990                 return klass.getAnnotationType();
1991             }
1992             public Map<Class<? extends Annotation>, Annotation> getDeclaredAnnotationMap(Class<?> klass) {
1993                 return klass.getDeclaredAnnotationMap();
1994             }
1995             public byte[] getRawClassAnnotations(Class<?> klass) {
1996                 return klass.getRawAnnotations();
1997             }
1998             public byte[] getRawClassTypeAnnotations(Class<?> klass) {
1999                 return klass.getRawTypeAnnotations();
2000             }
2001             public byte[] getRawExecutableTypeAnnotations(Executable executable) {
2002                 return Class.getExecutableTypeAnnotationBytes(executable);
2003             }
2004             public <E extends Enum<E>>
2005             E[] getEnumConstantsShared(Class<E> klass) {
2006                 return klass.getEnumConstantsShared();
2007             }
2008             public void blockedOn(Interruptible b) {
2009                 Thread.currentThread().blockedOn(b);
2010             }
2011             public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) {
2012                 Shutdown.add(slot, registerShutdownInProgress, hook);
2013             }
2014             @SuppressWarnings("removal")
2015             public void invokeFinalize(Object o) throws Throwable {
2016                 o.finalize();
2017             }
2018             public ConcurrentHashMap<?, ?> createOrGetClassLoaderValueMap(ClassLoader cl) {
2019                 return cl.createOrGetClassLoaderValueMap();
2020             }
2021             public Class<?> defineClass(ClassLoader loader, String name, byte[] b, ProtectionDomain pd, String source) {
2022                 return ClassLoader.defineClass1(loader, name, b, 0, b.length, pd, source);
2023             }
2024             public Class<?> defineClass(ClassLoader loader, Class<?> lookup, String name, byte[] b, ProtectionDomain pd,
2025                                         boolean initialize, int flags, Object classData) {
2026                 return ClassLoader.defineClass0(loader, lookup, name, b, 0, b.length, pd, initialize, flags, classData);
2027             }
2028             public Class<?> findBootstrapClassOrNull(String name) {
2029                 return ClassLoader.findBootstrapClassOrNull(name);
2030             }
2031             public Package definePackage(ClassLoader cl, String name, Module module) {
2032                 return cl.definePackage(name, module);
2033             }
2034             public Module defineModule(ClassLoader loader,
2035                                        ModuleDescriptor descriptor,
2036                                        URI uri) {
2037                 return new Module(null, loader, descriptor, uri);
2038             }
2039             public Module defineUnnamedModule(ClassLoader loader) {
2040                 return new Module(loader);
2041             }
2042             public void addReads(Module m1, Module m2) {
2043                 m1.implAddReads(m2);
2044             }
2045             public void addReadsAllUnnamed(Module m) {
2046                 m.implAddReadsAllUnnamed();
2047             }
2048             public void addExports(Module m, String pn) {
2049                 m.implAddExports(pn);
2050             }
2051             public void addExports(Module m, String pn, Module other) {
2052                 m.implAddExports(pn, other);
2053             }
2054             public void addExportsToAllUnnamed(Module m, String pn) {
2055                 m.implAddExportsToAllUnnamed(pn);
2056             }
2057             public void addOpens(Module m, String pn, Module other) {
2058                 m.implAddOpens(pn, other);
2059             }
2060             public void addOpensToAllUnnamed(Module m, String pn) {
2061                 m.implAddOpensToAllUnnamed(pn);
2062             }
2063             public void addOpensToAllUnnamed(Module m, Set<String> concealedPackages, Set<String> exportedPackages) {
2064                 m.implAddOpensToAllUnnamed(concealedPackages, exportedPackages);
2065             }
2066             public void addUses(Module m, Class<?> service) {
2067                 m.implAddUses(service);
2068             }
2069             public boolean isReflectivelyExported(Module m, String pn, Module other) {
2070                 return m.isReflectivelyExported(pn, other);
2071             }
2072             public boolean isReflectivelyOpened(Module m, String pn, Module other) {
2073                 return m.isReflectivelyOpened(pn, other);
2074             }
2075             public Module addEnableNativeAccess(Module m) {
2076                 return m.implAddEnableNativeAccess();
2077             }
2078             public boolean addEnableNativeAccess(ModuleLayer layer, String name) {
2079                 return layer.addEnableNativeAccess(name);
2080             }
2081             public void addEnableNativeAccessToAllUnnamed() {
2082                 Module.implAddEnableNativeAccessToAllUnnamed();
2083             }
2084             public void ensureNativeAccess(Module m, Class<?> owner, String methodName, Class<?> currentClass, boolean jni) {
2085                 m.ensureNativeAccess(owner, methodName, currentClass, jni);
2086             }
2087             public ServicesCatalog getServicesCatalog(ModuleLayer layer) {
2088                 return layer.getServicesCatalog();
2089             }
2090             public void bindToLoader(ModuleLayer layer, ClassLoader loader) {
2091                 layer.bindToLoader(loader);
2092             }
2093             public Stream<ModuleLayer> layers(ModuleLayer layer) {
2094                 return layer.layers();
2095             }
2096             public Stream<ModuleLayer> layers(ClassLoader loader) {
2097                 return ModuleLayer.layers(loader);
2098             }
2099 
2100             public int countPositives(byte[] bytes, int offset, int length) {
2101                 return StringCoding.countPositives(bytes, offset, length);
2102             }
2103             public int countNonZeroAscii(String s) {
2104                 return StringCoding.countNonZeroAscii(s);
2105             }
2106             public String newStringNoRepl(byte[] bytes, Charset cs) throws CharacterCodingException  {
2107                 return String.newStringNoRepl(bytes, cs);
2108             }
2109             public char getUTF16Char(byte[] bytes, int index) {
2110                 return StringUTF16.getChar(bytes, index);
2111             }
2112             public void putCharUTF16(byte[] bytes, int index, int ch) {
2113                 StringUTF16.putChar(bytes, index, ch);
2114             }
2115             public byte[] getBytesNoRepl(String s, Charset cs) throws CharacterCodingException {
2116                 return String.getBytesNoRepl(s, cs);
2117             }
2118 
2119             public String newStringUTF8NoRepl(byte[] bytes, int off, int len) {
2120                 return String.newStringUTF8NoRepl(bytes, off, len, true);
2121             }
2122 
2123             public byte[] getBytesUTF8NoRepl(String s) {
2124                 return String.getBytesUTF8NoRepl(s);
2125             }
2126 
2127             public void inflateBytesToChars(byte[] src, int srcOff, char[] dst, int dstOff, int len) {
2128                 StringLatin1.inflate(src, srcOff, dst, dstOff, len);
2129             }
2130 
2131             public int decodeASCII(byte[] src, int srcOff, char[] dst, int dstOff, int len) {
2132                 return String.decodeASCII(src, srcOff, dst, dstOff, len);
2133             }
2134 
2135             public int encodeASCII(char[] src, int srcOff, byte[] dst, int dstOff, int len) {
2136                 return StringCoding.implEncodeAsciiArray(src, srcOff, dst, dstOff, len);
2137             }
2138 
2139             public InputStream initialSystemIn() {
2140                 return initialIn;
2141             }
2142 
2143             public PrintStream initialSystemErr() {
2144                 return initialErr;
2145             }
2146 
2147             public void setCause(Throwable t, Throwable cause) {
2148                 t.setCause(cause);
2149             }
2150 
2151             public ProtectionDomain protectionDomain(Class<?> c) {
2152                 return c.protectionDomain();
2153             }
2154 
2155             public MethodHandle stringConcatHelper(String name, MethodType methodType) {
2156                 return StringConcatHelper.lookupStatic(name, methodType);
2157             }
2158 
2159             public long stringConcatInitialCoder() {
2160                 return StringConcatHelper.initialCoder();
2161             }
2162 
2163             public long stringConcatMix(long lengthCoder, String constant) {
2164                 return StringConcatHelper.mix(lengthCoder, constant);
2165             }
2166 
2167             public long stringConcatMix(long lengthCoder, char value) {
2168                 return StringConcatHelper.mix(lengthCoder, value);
2169             }
2170 
2171             public Object stringConcat1(String[] constants) {
2172                 return new StringConcatHelper.Concat1(constants);
2173             }
2174 
2175             public byte stringInitCoder() {
2176                 return String.COMPACT_STRINGS ? String.LATIN1 : String.UTF16;
2177             }
2178 
2179             public byte stringCoder(String str) {
2180                 return str.coder();
2181             }
2182 
2183             public int getCharsLatin1(long i, int index, byte[] buf) {
2184                 return StringLatin1.getChars(i, index, buf);
2185             }
2186 
2187             public int getCharsUTF16(long i, int index, byte[] buf) {
2188                 return StringUTF16.getChars(i, index, buf);
2189             }
2190 
2191             public String join(String prefix, String suffix, String delimiter, String[] elements, int size) {
2192                 return String.join(prefix, suffix, delimiter, elements, size);
2193             }
2194 
2195             public String concat(String prefix, Object value, String suffix) {
2196                 return StringConcatHelper.concat(prefix, value, suffix);
2197             }
2198 
2199             public Object classData(Class<?> c) {
2200                 return c.getClassData();
2201             }
2202 
2203             @Override
2204             public NativeLibraries nativeLibrariesFor(ClassLoader loader) {
2205                 return ClassLoader.nativeLibrariesFor(loader);
2206             }
2207 
2208             @Override
2209             public void exit(int statusCode) {
2210                 Shutdown.exit(statusCode);
2211             }
2212 
2213             public Thread[] getAllThreads() {
2214                 return Thread.getAllThreads();
2215             }
2216 
2217             public ThreadContainer threadContainer(Thread thread) {
2218                 return thread.threadContainer();
2219             }
2220 
2221             public void start(Thread thread, ThreadContainer container) {
2222                 thread.start(container);
2223             }
2224 
2225             public StackableScope headStackableScope(Thread thread) {
2226                 return thread.headStackableScopes();
2227             }
2228 
2229             public void setHeadStackableScope(StackableScope scope) {
2230                 Thread.setHeadStackableScope(scope);
2231             }
2232 
2233             public Thread currentCarrierThread() {
2234                 return Thread.currentCarrierThread();
2235             }
2236 
2237             public <T> T getCarrierThreadLocal(CarrierThreadLocal<T> local) {
2238                 return ((ThreadLocal<T>)local).getCarrierThreadLocal();
2239             }
2240 
2241             public <T> void setCarrierThreadLocal(CarrierThreadLocal<T> local, T value) {
2242                 ((ThreadLocal<T>)local).setCarrierThreadLocal(value);
2243             }
2244 
2245             public void removeCarrierThreadLocal(CarrierThreadLocal<?> local) {
2246                 ((ThreadLocal<?>)local).removeCarrierThreadLocal();
2247             }
2248 
2249             public boolean isCarrierThreadLocalPresent(CarrierThreadLocal<?> local) {
2250                 return ((ThreadLocal<?>)local).isCarrierThreadLocalPresent();
2251             }
2252 
2253             public Object[] scopedValueCache() {
2254                 return Thread.scopedValueCache();
2255             }
2256 
2257             public void setScopedValueCache(Object[] cache) {
2258                 Thread.setScopedValueCache(cache);
2259             }
2260 
2261             public Object scopedValueBindings() {
2262                 return Thread.scopedValueBindings();
2263             }
2264 
2265             public Continuation getContinuation(Thread thread) {
2266                 return thread.getContinuation();
2267             }
2268 
2269             public void setContinuation(Thread thread, Continuation continuation) {
2270                 thread.setContinuation(continuation);
2271             }
2272 
2273             public ContinuationScope virtualThreadContinuationScope() {
2274                 return VirtualThread.continuationScope();
2275             }
2276 
2277             public void parkVirtualThread() {
2278                 Thread thread = Thread.currentThread();
2279                 if (thread instanceof BaseVirtualThread vthread) {
2280                     vthread.park();
2281                 } else {
2282                     throw new WrongThreadException();
2283                 }
2284             }
2285 
2286             public void parkVirtualThread(long nanos) {
2287                 Thread thread = Thread.currentThread();
2288                 if (thread instanceof BaseVirtualThread vthread) {
2289                     vthread.parkNanos(nanos);
2290                 } else {
2291                     throw new WrongThreadException();
2292                 }
2293             }
2294 
2295             public void unparkVirtualThread(Thread thread) {
2296                 if (thread instanceof BaseVirtualThread vthread) {
2297                     vthread.unpark();
2298                 } else {
2299                     throw new WrongThreadException();
2300                 }
2301             }
2302 
2303             public Executor virtualThreadDefaultScheduler() {
2304                 return VirtualThread.defaultScheduler();
2305             }
2306 
2307             public Stream<ScheduledExecutorService> virtualThreadDelayedTaskSchedulers() {
2308                 return VirtualThread.delayedTaskSchedulers();
2309             }
2310 
2311             public StackWalker newStackWalkerInstance(Set<StackWalker.Option> options,
2312                                                       ContinuationScope contScope,
2313                                                       Continuation continuation) {
2314                 return StackWalker.newInstance(options, null, contScope, continuation);
2315             }
2316 
2317             public int classFileFormatVersion(Class<?> clazz) {
2318                 return clazz.getClassFileVersion();
2319             }
2320 
2321             public String getLoaderNameID(ClassLoader loader) {
2322                 return loader != null ? loader.nameAndId() : "null";
2323             }
2324 
2325             @Override
2326             public void copyToSegmentRaw(String string, MemorySegment segment, long offset) {
2327                 string.copyToSegmentRaw(segment, offset);
2328             }
2329 
2330             @Override
2331             public boolean bytesCompatible(String string, Charset charset) {
2332                 return string.bytesCompatible(charset);
2333             }
2334         });
2335     }
2336 }