1 /*
   2  * Copyright (c) 1994, 2019, 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.PrintStream;
  36 import java.io.UnsupportedEncodingException;
  37 import java.lang.annotation.Annotation;
  38 import java.lang.module.ModuleDescriptor;
  39 import java.lang.reflect.Constructor;
  40 import java.lang.reflect.Executable;
  41 import java.lang.reflect.Method;
  42 import java.lang.reflect.Modifier;
  43 import java.net.URI;
  44 import java.nio.charset.CharacterCodingException;
  45 import java.security.AccessControlContext;
  46 import java.security.ProtectionDomain;
  47 import java.security.AccessController;
  48 import java.security.PrivilegedAction;
  49 import java.nio.channels.Channel;
  50 import java.nio.channels.spi.SelectorProvider;
  51 import java.nio.charset.Charset;
  52 import java.util.Iterator;
  53 import java.util.List;
  54 import java.util.Map;
  55 import java.util.Objects;
  56 import java.util.Properties;
  57 import java.util.PropertyPermission;
  58 import java.util.ResourceBundle;
  59 import java.util.function.Supplier;
  60 import java.util.concurrent.ConcurrentHashMap;
  61 import java.util.stream.Stream;
  62 
  63 import jdk.internal.util.StaticProperty;
  64 import jdk.internal.module.ModuleBootstrap;
  65 import jdk.internal.module.ServicesCatalog;
  66 import jdk.internal.reflect.CallerSensitive;
  67 import jdk.internal.reflect.Reflection;
  68 import jdk.internal.HotSpotIntrinsicCandidate;
  69 import jdk.internal.access.JavaLangAccess;
  70 import jdk.internal.access.SharedSecrets;
  71 import jdk.internal.misc.VM;
  72 import jdk.internal.logger.LoggerFinderLoader;
  73 import jdk.internal.logger.LazyLoggers;
  74 import jdk.internal.logger.LocalizedLoggerWrapper;
  75 import jdk.internal.util.SystemProps;
  76 import jdk.internal.vm.annotation.Stable;
  77 import sun.reflect.annotation.AnnotationType;
  78 import sun.nio.ch.Interruptible;
  79 import sun.security.util.SecurityConstants;
  80 
  81 /**
  82  * The {@code System} class contains several useful class fields
  83  * and methods. It cannot be instantiated.
  84  *
  85  * Among the facilities provided by the {@code System} class
  86  * are standard input, standard output, and error output streams;
  87  * access to externally defined properties and environment
  88  * variables; a means of loading files and libraries; and a utility
  89  * method for quickly copying a portion of an array.
  90  *
  91  * @since   1.0
  92  */
  93 public final class System {
  94     /* Register the natives via the static initializer.
  95      *
  96      * VM will invoke the initializeSystemClass method to complete
  97      * the initialization for this class separated from clinit.
  98      * Note that to use properties set by the VM, see the constraints
  99      * described in the initializeSystemClass method.
 100      */
 101     private static native void registerNatives();
 102     static {
 103         registerNatives();
 104     }
 105 
 106     /** Don't let anyone instantiate this class */
 107     private System() {
 108     }
 109 
 110     /**
 111      * The "standard" input stream. This stream is already
 112      * open and ready to supply input data. Typically this stream
 113      * corresponds to keyboard input or another input source specified by
 114      * the host environment or user.
 115      */
 116     public static final InputStream in = null;
 117 
 118     /**
 119      * The "standard" output stream. This stream is already
 120      * open and ready to accept output data. Typically this stream
 121      * corresponds to display output or another output destination
 122      * specified by the host environment or user.
 123      * <p>
 124      * For simple stand-alone Java applications, a typical way to write
 125      * a line of output data is:
 126      * <blockquote><pre>
 127      *     System.out.println(data)
 128      * </pre></blockquote>
 129      * <p>
 130      * See the {@code println} methods in class {@code PrintStream}.
 131      *
 132      * @see     java.io.PrintStream#println()
 133      * @see     java.io.PrintStream#println(boolean)
 134      * @see     java.io.PrintStream#println(char)
 135      * @see     java.io.PrintStream#println(char[])
 136      * @see     java.io.PrintStream#println(double)
 137      * @see     java.io.PrintStream#println(float)
 138      * @see     java.io.PrintStream#println(int)
 139      * @see     java.io.PrintStream#println(long)
 140      * @see     java.io.PrintStream#println(java.lang.Object)
 141      * @see     java.io.PrintStream#println(java.lang.String)
 142      */
 143     public static final PrintStream out = null;
 144 
 145     /**
 146      * The "standard" error output stream. This stream is already
 147      * open and ready to accept output data.
 148      * <p>
 149      * Typically this stream corresponds to display output or another
 150      * output destination specified by the host environment or user. By
 151      * convention, this output stream is used to display error messages
 152      * or other information that should come to the immediate attention
 153      * of a user even if the principal output stream, the value of the
 154      * variable {@code out}, has been redirected to a file or other
 155      * destination that is typically not continuously monitored.
 156      */
 157     public static final PrintStream err = null;
 158 
 159     // indicates if a security manager is possible
 160     private static final int NEVER = 1;
 161     private static final int MAYBE = 2;
 162     private static @Stable int allowSecurityManager;
 163 
 164     // current security manager
 165     private static volatile SecurityManager security;   // read by VM
 166 
 167     // return true if a security manager is allowed
 168     private static boolean allowSecurityManager() {
 169         return (allowSecurityManager != NEVER);
 170     }
 171 
 172     /**
 173      * Reassigns the "standard" input stream.
 174      *
 175      * First, if there is a security manager, its {@code checkPermission}
 176      * method is called with a {@code RuntimePermission("setIO")} permission
 177      *  to see if it's ok to reassign the "standard" input stream.
 178      *
 179      * @param in the new standard input stream.
 180      *
 181      * @throws SecurityException
 182      *        if a security manager exists and its
 183      *        {@code checkPermission} method doesn't allow
 184      *        reassigning of the standard input stream.
 185      *
 186      * @see SecurityManager#checkPermission
 187      * @see java.lang.RuntimePermission
 188      *
 189      * @since   1.1
 190      */
 191     public static void setIn(InputStream in) {
 192         checkIO();
 193         setIn0(in);
 194     }
 195 
 196     /**
 197      * Reassigns the "standard" output stream.
 198      *
 199      * First, if there is a security manager, its {@code checkPermission}
 200      * method is called with a {@code RuntimePermission("setIO")} permission
 201      *  to see if it's ok to reassign the "standard" output stream.
 202      *
 203      * @param out the new standard output stream
 204      *
 205      * @throws SecurityException
 206      *        if a security manager exists and its
 207      *        {@code checkPermission} method doesn't allow
 208      *        reassigning of the standard output stream.
 209      *
 210      * @see SecurityManager#checkPermission
 211      * @see java.lang.RuntimePermission
 212      *
 213      * @since   1.1
 214      */
 215     public static void setOut(PrintStream out) {
 216         checkIO();
 217         setOut0(out);
 218     }
 219 
 220     /**
 221      * Reassigns the "standard" error output stream.
 222      *
 223      * First, if there is a security manager, its {@code checkPermission}
 224      * method is called with a {@code RuntimePermission("setIO")} permission
 225      *  to see if it's ok to reassign the "standard" error output stream.
 226      *
 227      * @param err the new standard error output stream.
 228      *
 229      * @throws SecurityException
 230      *        if a security manager exists and its
 231      *        {@code checkPermission} method doesn't allow
 232      *        reassigning of the standard error output stream.
 233      *
 234      * @see SecurityManager#checkPermission
 235      * @see java.lang.RuntimePermission
 236      *
 237      * @since   1.1
 238      */
 239     public static void setErr(PrintStream err) {
 240         checkIO();
 241         setErr0(err);
 242     }
 243 
 244     private static volatile Console cons;
 245 
 246     /**
 247      * Returns the unique {@link java.io.Console Console} object associated
 248      * with the current Java virtual machine, if any.
 249      *
 250      * @return  The system console, if any, otherwise {@code null}.
 251      *
 252      * @since   1.6
 253      */
 254      public static Console console() {
 255          Console c;
 256          if ((c = cons) == null) {
 257              synchronized (System.class) {
 258                  if ((c = cons) == null) {
 259                      cons = c = SharedSecrets.getJavaIOAccess().console();
 260                  }
 261              }
 262          }
 263          return c;
 264      }
 265 
 266     /**
 267      * Returns the channel inherited from the entity that created this
 268      * Java virtual machine.
 269      *
 270      * This method returns the channel obtained by invoking the
 271      * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
 272      * inheritedChannel} method of the system-wide default
 273      * {@link java.nio.channels.spi.SelectorProvider} object.
 274      *
 275      * <p> In addition to the network-oriented channels described in
 276      * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
 277      * inheritedChannel}, this method may return other kinds of
 278      * channels in the future.
 279      *
 280      * @return  The inherited channel, if any, otherwise {@code null}.
 281      *
 282      * @throws  IOException
 283      *          If an I/O error occurs
 284      *
 285      * @throws  SecurityException
 286      *          If a security manager is present and it does not
 287      *          permit access to the channel.
 288      *
 289      * @since 1.5
 290      */
 291     public static Channel inheritedChannel() throws IOException {
 292         return SelectorProvider.provider().inheritedChannel();
 293     }
 294 
 295     private static void checkIO() {
 296         SecurityManager sm = getSecurityManager();
 297         if (sm != null) {
 298             sm.checkPermission(new RuntimePermission("setIO"));
 299         }
 300     }
 301 
 302     private static native void setIn0(InputStream in);
 303     private static native void setOut0(PrintStream out);
 304     private static native void setErr0(PrintStream err);
 305 
 306     /**
 307      * Sets the system-wide security manager.
 308      *
 309      * If there is a security manager already installed, this method first
 310      * calls the security manager's {@code checkPermission} method
 311      * with a {@code RuntimePermission("setSecurityManager")}
 312      * permission to ensure it's ok to replace the existing
 313      * security manager.
 314      * This may result in throwing a {@code SecurityException}.
 315      *
 316      * <p> Otherwise, the argument is established as the current
 317      * security manager. If the argument is {@code null} and no
 318      * security manager has been established, then no action is taken and
 319      * the method simply returns.
 320      *
 321      * @implNote In the JDK implementation, if the Java virtual machine is
 322      * started with the system property {@code java.security.manager} set to
 323      * the special token "{@code disallow}" then the {@code setSecurityManager}
 324      * method cannot be used to set a security manager.
 325      *
 326      * @param  sm the security manager or {@code null}
 327      * @throws SecurityException
 328      *         if the security manager has already been set and its {@code
 329      *         checkPermission} method doesn't allow it to be replaced
 330      * @throws UnsupportedOperationException
 331      *         if {@code sm} is non-null and a security manager is not allowed
 332      *         to be set dynamically
 333      * @see #getSecurityManager
 334      * @see SecurityManager#checkPermission
 335      * @see java.lang.RuntimePermission
 336      */
 337     public static void setSecurityManager(SecurityManager sm) {
 338         if (allowSecurityManager()) {
 339             if (security == null) {
 340                 // ensure image reader is initialized
 341                 Object.class.getResource("java/lang/ANY");
 342             }
 343             if (sm != null) {
 344                 try {
 345                     // pre-populates the SecurityManager.packageAccess cache
 346                     // to avoid recursive permission checking issues with custom
 347                     // SecurityManager implementations
 348                     sm.checkPackageAccess("java.lang");
 349                 } catch (Exception e) {
 350                     // no-op
 351                 }
 352             }
 353             setSecurityManager0(sm);
 354         } else {
 355             // security manager not allowed
 356             if (sm != null) {
 357                 throw new UnsupportedOperationException(
 358                     "Runtime configured to disallow security manager");
 359             }
 360         }
 361     }
 362 
 363     private static synchronized
 364     void setSecurityManager0(final SecurityManager s) {
 365         SecurityManager sm = getSecurityManager();
 366         if (sm != null) {
 367             // ask the currently installed security manager if we
 368             // can replace it.
 369             sm.checkPermission(new RuntimePermission("setSecurityManager"));
 370         }
 371 
 372         if ((s != null) && (s.getClass().getClassLoader() != null)) {
 373             // New security manager class is not on bootstrap classpath.
 374             // Force policy to get initialized before we install the new
 375             // security manager, in order to prevent infinite loops when
 376             // trying to initialize the policy (which usually involves
 377             // accessing some security and/or system properties, which in turn
 378             // calls the installed security manager's checkPermission method
 379             // which will loop infinitely if there is a non-system class
 380             // (in this case: the new security manager class) on the stack).
 381             AccessController.doPrivileged(new PrivilegedAction<>() {
 382                 public Object run() {
 383                     s.getClass().getProtectionDomain().implies
 384                         (SecurityConstants.ALL_PERMISSION);
 385                     return null;
 386                 }
 387             });
 388         }
 389 
 390         security = s;
 391     }
 392 
 393     /**
 394      * Gets the system-wide security manager.
 395      *
 396      * @return  if a security manager has already been established for the
 397      *          current application, then that security manager is returned;
 398      *          otherwise, {@code null} is returned.
 399      * @see     #setSecurityManager
 400      */
 401     public static SecurityManager getSecurityManager() {
 402         if (allowSecurityManager()) {
 403             return security;
 404         } else {
 405             return null;
 406         }
 407     }
 408 
 409     /**
 410      * Returns the current time in milliseconds.  Note that
 411      * while the unit of time of the return value is a millisecond,
 412      * the granularity of the value depends on the underlying
 413      * operating system and may be larger.  For example, many
 414      * operating systems measure time in units of tens of
 415      * milliseconds.
 416      *
 417      * <p> See the description of the class {@code Date} for
 418      * a discussion of slight discrepancies that may arise between
 419      * "computer time" and coordinated universal time (UTC).
 420      *
 421      * @return  the difference, measured in milliseconds, between
 422      *          the current time and midnight, January 1, 1970 UTC.
 423      * @see     java.util.Date
 424      */
 425     @HotSpotIntrinsicCandidate
 426     public static native long currentTimeMillis();
 427 
 428     /**
 429      * Returns the current value of the running Java Virtual Machine's
 430      * high-resolution time source, in nanoseconds.
 431      *
 432      * This method can only be used to measure elapsed time and is
 433      * not related to any other notion of system or wall-clock time.
 434      * The value returned represents nanoseconds since some fixed but
 435      * arbitrary <i>origin</i> time (perhaps in the future, so values
 436      * may be negative).  The same origin is used by all invocations of
 437      * this method in an instance of a Java virtual machine; other
 438      * virtual machine instances are likely to use a different origin.
 439      *
 440      * <p>This method provides nanosecond precision, but not necessarily
 441      * nanosecond resolution (that is, how frequently the value changes)
 442      * - no guarantees are made except that the resolution is at least as
 443      * good as that of {@link #currentTimeMillis()}.
 444      *
 445      * <p>Differences in successive calls that span greater than
 446      * approximately 292 years (2<sup>63</sup> nanoseconds) will not
 447      * correctly compute elapsed time due to numerical overflow.
 448      *
 449      * <p>The values returned by this method become meaningful only when
 450      * the difference between two such values, obtained within the same
 451      * instance of a Java virtual machine, is computed.
 452      *
 453      * <p>For example, to measure how long some code takes to execute:
 454      * <pre> {@code
 455      * long startTime = System.nanoTime();
 456      * // ... the code being measured ...
 457      * long elapsedNanos = System.nanoTime() - startTime;}</pre>
 458      *
 459      * <p>To compare elapsed time against a timeout, use <pre> {@code
 460      * if (System.nanoTime() - startTime >= timeoutNanos) ...}</pre>
 461      * instead of <pre> {@code
 462      * if (System.nanoTime() >= startTime + timeoutNanos) ...}</pre>
 463      * because of the possibility of numerical overflow.
 464      *
 465      * @return the current value of the running Java Virtual Machine's
 466      *         high-resolution time source, in nanoseconds
 467      * @since 1.5
 468      */
 469     @HotSpotIntrinsicCandidate
 470     public static native long nanoTime();
 471 
 472     /**
 473      * Copies an array from the specified source array, beginning at the
 474      * specified position, to the specified position of the destination array.
 475      * A subsequence of array components are copied from the source
 476      * array referenced by {@code src} to the destination array
 477      * referenced by {@code dest}. The number of components copied is
 478      * equal to the {@code length} argument. The components at
 479      * positions {@code srcPos} through
 480      * {@code srcPos+length-1} in the source array are copied into
 481      * positions {@code destPos} through
 482      * {@code destPos+length-1}, respectively, of the destination
 483      * array.
 484      * <p>
 485      * If the {@code src} and {@code dest} arguments refer to the
 486      * same array object, then the copying is performed as if the
 487      * components at positions {@code srcPos} through
 488      * {@code srcPos+length-1} were first copied to a temporary
 489      * array with {@code length} components and then the contents of
 490      * the temporary array were copied into positions
 491      * {@code destPos} through {@code destPos+length-1} of the
 492      * destination array.
 493      * <p>
 494      * If {@code dest} is {@code null}, then a
 495      * {@code NullPointerException} is thrown.
 496      * <p>
 497      * If {@code src} is {@code null}, then a
 498      * {@code NullPointerException} is thrown and the destination
 499      * array is not modified.
 500      * <p>
 501      * Otherwise, if any of the following is true, an
 502      * {@code ArrayStoreException} is thrown and the destination is
 503      * not modified:
 504      * <ul>
 505      * <li>The {@code src} argument refers to an object that is not an
 506      *     array.
 507      * <li>The {@code dest} argument refers to an object that is not an
 508      *     array.
 509      * <li>The {@code src} argument and {@code dest} argument refer
 510      *     to arrays whose component types are different primitive types.
 511      * <li>The {@code src} argument refers to an array with a primitive
 512      *    component type and the {@code dest} argument refers to an array
 513      *     with a reference component type.
 514      * <li>The {@code src} argument refers to an array with a reference
 515      *    component type and the {@code dest} argument refers to an array
 516      *     with a primitive component type.
 517      * </ul>
 518      * <p>
 519      * Otherwise, if any of the following is true, an
 520      * {@code IndexOutOfBoundsException} is
 521      * thrown and the destination is not modified:
 522      * <ul>
 523      * <li>The {@code srcPos} argument is negative.
 524      * <li>The {@code destPos} argument is negative.
 525      * <li>The {@code length} argument is negative.
 526      * <li>{@code srcPos+length} is greater than
 527      *     {@code src.length}, the length of the source array.
 528      * <li>{@code destPos+length} is greater than
 529      *     {@code dest.length}, the length of the destination array.
 530      * </ul>
 531      * <p>
 532      * Otherwise, if any actual component of the source array from
 533      * position {@code srcPos} through
 534      * {@code srcPos+length-1} cannot be converted to the component
 535      * type of the destination array by assignment conversion, an
 536      * {@code ArrayStoreException} is thrown. In this case, let
 537      * <b><i>k</i></b> be the smallest nonnegative integer less than
 538      * length such that {@code src[srcPos+}<i>k</i>{@code ]}
 539      * cannot be converted to the component type of the destination
 540      * array; when the exception is thrown, source array components from
 541      * positions {@code srcPos} through
 542      * {@code srcPos+}<i>k</i>{@code -1}
 543      * will already have been copied to destination array positions
 544      * {@code destPos} through
 545      * {@code destPos+}<i>k</I>{@code -1} and no other
 546      * positions of the destination array will have been modified.
 547      * (Because of the restrictions already itemized, this
 548      * paragraph effectively applies only to the situation where both
 549      * arrays have component types that are reference types.)
 550      *
 551      * @param      src      the source array.
 552      * @param      srcPos   starting position in the source array.
 553      * @param      dest     the destination array.
 554      * @param      destPos  starting position in the destination data.
 555      * @param      length   the number of array elements to be copied.
 556      * @throws     IndexOutOfBoundsException  if copying would cause
 557      *             access of data outside array bounds.
 558      * @throws     ArrayStoreException  if an element in the {@code src}
 559      *             array could not be stored into the {@code dest} array
 560      *             because of a type mismatch.
 561      * @throws     NullPointerException if either {@code src} or
 562      *             {@code dest} is {@code null}.
 563      */
 564     @HotSpotIntrinsicCandidate
 565     public static native void arraycopy(Object src,  int  srcPos,
 566                                         Object dest, int destPos,
 567                                         int length);
 568 
 569     /**
 570      * Returns the same hash code for the given object as
 571      * would be returned by the default method hashCode(),
 572      * whether or not the given object's class overrides
 573      * hashCode().
 574      * The hash code for the null reference is zero.
 575      *
 576      * @param x object for which the hashCode is to be calculated
 577      * @return  the hashCode
 578      * @since   1.1
 579      * @see Object#hashCode
 580      * @see java.util.Objects#hashCode(Object)
 581      */
 582     @HotSpotIntrinsicCandidate
 583     public static native int identityHashCode(Object x);
 584 
 585     /**
 586      * System properties. The following properties are guaranteed to be defined:
 587      * <dl>
 588      * <dt>java.version         <dd>Java version number
 589      * <dt>java.version.date    <dd>Java version date
 590      * <dt>java.vendor          <dd>Java vendor specific string
 591      * <dt>java.vendor.url      <dd>Java vendor URL
 592      * <dt>java.vendor.version  <dd>Java vendor version
 593      * <dt>java.home            <dd>Java installation directory
 594      * <dt>java.class.version   <dd>Java class version number
 595      * <dt>java.class.path      <dd>Java classpath
 596      * <dt>os.name              <dd>Operating System Name
 597      * <dt>os.arch              <dd>Operating System Architecture
 598      * <dt>os.version           <dd>Operating System Version
 599      * <dt>file.separator       <dd>File separator ("/" on Unix)
 600      * <dt>path.separator       <dd>Path separator (":" on Unix)
 601      * <dt>line.separator       <dd>Line separator ("\n" on Unix)
 602      * <dt>user.name            <dd>User account name
 603      * <dt>user.home            <dd>User home directory
 604      * <dt>user.dir             <dd>User's current working directory
 605      * </dl>
 606      */
 607 
 608     private static Properties props;
 609 
 610     /**
 611      * Determines the current system properties.
 612      *
 613      * First, if there is a security manager, its
 614      * {@code checkPropertiesAccess} method is called with no
 615      * arguments. This may result in a security exception.
 616      * <p>
 617      * The current set of system properties for use by the
 618      * {@link #getProperty(String)} method is returned as a
 619      * {@code Properties} object. If there is no current set of
 620      * system properties, a set of system properties is first created and
 621      * initialized. This set of system properties always includes values
 622      * for the following keys:
 623      * <table class="striped" style="text-align:left">
 624      * <caption style="display:none">Shows property keys and associated values</caption>
 625      * <thead>
 626      * <tr><th scope="col">Key</th>
 627      *     <th scope="col">Description of Associated Value</th></tr>
 628      * </thead>
 629      * <tbody>
 630      * <tr><th scope="row">{@systemProperty java.version}</th>
 631      *     <td>Java Runtime Environment version, which may be interpreted
 632      *     as a {@link Runtime.Version}</td></tr>
 633      * <tr><th scope="row">{@systemProperty java.version.date}</th>
 634      *     <td>Java Runtime Environment version date, in ISO-8601 YYYY-MM-DD
 635      *     format, which may be interpreted as a {@link
 636      *     java.time.LocalDate}</td></tr>
 637      * <tr><th scope="row">{@systemProperty java.vendor}</th>
 638      *     <td>Java Runtime Environment vendor</td></tr>
 639      * <tr><th scope="row">{@systemProperty java.vendor.url}</th>
 640      *     <td>Java vendor URL</td></tr>
 641      * <tr><th scope="row">{@systemProperty java.vendor.version}</th>
 642      *     <td>Java vendor version</td></tr>
 643      * <tr><th scope="row">{@systemProperty java.home}</th>
 644      *     <td>Java installation directory</td></tr>
 645      * <tr><th scope="row">{@systemProperty java.vm.specification.version}</th>
 646      *     <td>Java Virtual Machine specification version, whose value is the
 647      *     {@linkplain Runtime.Version#feature feature} element of the
 648      *     {@linkplain Runtime#version() runtime version}</td></tr>
 649      * <tr><th scope="row">{@systemProperty java.vm.specification.vendor}</th>
 650      *     <td>Java Virtual Machine specification vendor</td></tr>
 651      * <tr><th scope="row">{@systemProperty java.vm.specification.name}</th>
 652      *     <td>Java Virtual Machine specification name</td></tr>
 653      * <tr><th scope="row">{@systemProperty java.vm.version}</th>
 654      *     <td>Java Virtual Machine implementation version which may be
 655      *     interpreted as a {@link Runtime.Version}</td></tr>
 656      * <tr><th scope="row">{@systemProperty java.vm.vendor}</th>
 657      *     <td>Java Virtual Machine implementation vendor</td></tr>
 658      * <tr><th scope="row">{@systemProperty java.vm.name}</th>
 659      *     <td>Java Virtual Machine implementation name</td></tr>
 660      * <tr><th scope="row">{@systemProperty java.specification.version}</th>
 661      *     <td>Java Runtime Environment specification version, whose value is
 662      *     the {@linkplain Runtime.Version#feature feature} element of the
 663      *     {@linkplain Runtime#version() runtime version}</td></tr>
 664      * <tr><th scope="row">{@systemProperty java.specification.vendor}</th>
 665      *     <td>Java Runtime Environment specification  vendor</td></tr>
 666      * <tr><th scope="row">{@systemProperty java.specification.name}</th>
 667      *     <td>Java Runtime Environment specification  name</td></tr>
 668      * <tr><th scope="row">{@systemProperty java.class.version}</th>
 669      *     <td>Java class format version number</td></tr>
 670      * <tr><th scope="row">{@systemProperty java.class.path}</th>
 671      *     <td>Java class path  (refer to
 672      *        {@link ClassLoader#getSystemClassLoader()} for details)</td></tr>
 673      * <tr><th scope="row">{@systemProperty java.library.path}</th>
 674      *     <td>List of paths to search when loading libraries</td></tr>
 675      * <tr><th scope="row">{@systemProperty java.io.tmpdir}</th>
 676      *     <td>Default temp file path</td></tr>
 677      * <tr><th scope="row">{@systemProperty java.compiler}</th>
 678      *     <td>Name of JIT compiler to use</td></tr>
 679      * <tr><th scope="row">{@systemProperty os.name}</th>
 680      *     <td>Operating system name</td></tr>
 681      * <tr><th scope="row">{@systemProperty os.arch}</th>
 682      *     <td>Operating system architecture</td></tr>
 683      * <tr><th scope="row">{@systemProperty os.version}</th>
 684      *     <td>Operating system version</td></tr>
 685      * <tr><th scope="row">{@systemProperty file.separator}</th>
 686      *     <td>File separator ("/" on UNIX)</td></tr>
 687      * <tr><th scope="row">{@systemProperty path.separator}</th>
 688      *     <td>Path separator (":" on UNIX)</td></tr>
 689      * <tr><th scope="row">{@systemProperty line.separator}</th>
 690      *     <td>Line separator ("\n" on UNIX)</td></tr>
 691      * <tr><th scope="row">{@systemProperty user.name}</th>
 692      *     <td>User's account name</td></tr>
 693      * <tr><th scope="row">{@systemProperty user.home}</th>
 694      *     <td>User's home directory</td></tr>
 695      * <tr><th scope="row">{@systemProperty user.dir}</th>
 696      *     <td>User's current working directory</td></tr>
 697      * </tbody>
 698      * </table>
 699      * <p>
 700      * Multiple paths in a system property value are separated by the path
 701      * separator character of the platform.
 702      * <p>
 703      * Note that even if the security manager does not permit the
 704      * {@code getProperties} operation, it may choose to permit the
 705      * {@link #getProperty(String)} operation.
 706      *
 707      * @apiNote
 708      * <strong>Changing a standard system property may have unpredictable results
 709      * unless otherwise specified.</strong>
 710      * Property values may be cached during initialization or on first use.
 711      * Setting a standard property after initialization using {@link #getProperties()},
 712      * {@link #setProperties(Properties)}, {@link #setProperty(String, String)}, or
 713      * {@link #clearProperty(String)} may not have the desired effect.
 714      *
 715      * @implNote
 716      * In addition to the standard system properties, the system
 717      * properties may include the following keys:
 718      * <table class="striped">
 719      * <caption style="display:none">Shows property keys and associated values</caption>
 720      * <thead>
 721      * <tr><th scope="col">Key</th>
 722      *     <th scope="col">Description of Associated Value</th></tr>
 723      * </thead>
 724      * <tbody>
 725      * <tr><th scope="row">{@systemProperty jdk.module.path}</th>
 726      *     <td>The application module path</td></tr>
 727      * <tr><th scope="row">{@systemProperty jdk.module.upgrade.path}</th>
 728      *     <td>The upgrade module path</td></tr>
 729      * <tr><th scope="row">{@systemProperty jdk.module.main}</th>
 730      *     <td>The module name of the initial/main module</td></tr>
 731      * <tr><th scope="row">{@systemProperty jdk.module.main.class}</th>
 732      *     <td>The main class name of the initial module</td></tr>
 733      * </tbody>
 734      * </table>
 735      *
 736      * @return     the system properties
 737      * @throws     SecurityException  if a security manager exists and its
 738      *             {@code checkPropertiesAccess} method doesn't allow access
 739      *             to the system properties.
 740      * @see        #setProperties
 741      * @see        java.lang.SecurityException
 742      * @see        java.lang.SecurityManager#checkPropertiesAccess()
 743      * @see        java.util.Properties
 744      */
 745     public static Properties getProperties() {
 746         SecurityManager sm = getSecurityManager();
 747         if (sm != null) {
 748             sm.checkPropertiesAccess();
 749         }
 750 
 751         return props;
 752     }
 753 
 754     /**
 755      * Returns the system-dependent line separator string.  It always
 756      * returns the same value - the initial value of the {@linkplain
 757      * #getProperty(String) system property} {@code line.separator}.
 758      *
 759      * <p>On UNIX systems, it returns {@code "\n"}; on Microsoft
 760      * Windows systems it returns {@code "\r\n"}.
 761      *
 762      * @return the system-dependent line separator string
 763      * @since 1.7
 764      */
 765     public static String lineSeparator() {
 766         return lineSeparator;
 767     }
 768 
 769     private static String lineSeparator;
 770 
 771     /**
 772      * Sets the system properties to the {@code Properties} argument.
 773      *
 774      * First, if there is a security manager, its
 775      * {@code checkPropertiesAccess} method is called with no
 776      * arguments. This may result in a security exception.
 777      * <p>
 778      * The argument becomes the current set of system properties for use
 779      * by the {@link #getProperty(String)} method. If the argument is
 780      * {@code null}, then the current set of system properties is
 781      * forgotten.
 782      *
 783      * @apiNote
 784      * <strong>Changing a standard system property may have unpredictable results
 785      * unless otherwise specified</strong>.
 786      * See {@linkplain #getProperties getProperties} for details.
 787      *
 788      * @param      props   the new system properties.
 789      * @throws     SecurityException  if a security manager exists and its
 790      *             {@code checkPropertiesAccess} method doesn't allow access
 791      *             to the system properties.
 792      * @see        #getProperties
 793      * @see        java.util.Properties
 794      * @see        java.lang.SecurityException
 795      * @see        java.lang.SecurityManager#checkPropertiesAccess()
 796      */
 797     public static void setProperties(Properties props) {
 798         SecurityManager sm = getSecurityManager();
 799         if (sm != null) {
 800             sm.checkPropertiesAccess();
 801         }
 802 
 803         if (props == null) {
 804             Map<String, String> tempProps = SystemProps.initProperties();
 805             VersionProps.init(tempProps);
 806             props = createProperties(tempProps);
 807         }
 808         System.props = props;
 809     }
 810 
 811     /**
 812      * Gets the system property indicated by the specified key.
 813      *
 814      * First, if there is a security manager, its
 815      * {@code checkPropertyAccess} method is called with the key as
 816      * its argument. This may result in a SecurityException.
 817      * <p>
 818      * If there is no current set of system properties, a set of system
 819      * properties is first created and initialized in the same manner as
 820      * for the {@code getProperties} method.
 821      *
 822      * @apiNote
 823      * <strong>Changing a standard system property may have unpredictable results
 824      * unless otherwise specified</strong>.
 825      * See {@linkplain #getProperties getProperties} for details.
 826      *
 827      * @param      key   the name of the system property.
 828      * @return     the string value of the system property,
 829      *             or {@code null} if there is no property with that key.
 830      *
 831      * @throws     SecurityException  if a security manager exists and its
 832      *             {@code checkPropertyAccess} method doesn't allow
 833      *             access to the specified system property.
 834      * @throws     NullPointerException if {@code key} is {@code null}.
 835      * @throws     IllegalArgumentException if {@code key} is empty.
 836      * @see        #setProperty
 837      * @see        java.lang.SecurityException
 838      * @see        java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
 839      * @see        java.lang.System#getProperties()
 840      */
 841     public static String getProperty(String key) {
 842         checkKey(key);
 843         SecurityManager sm = getSecurityManager();
 844         if (sm != null) {
 845             sm.checkPropertyAccess(key);
 846         }
 847 
 848         return props.getProperty(key);
 849     }
 850 
 851     /**
 852      * Gets the system property indicated by the specified key.
 853      *
 854      * First, if there is a security manager, its
 855      * {@code checkPropertyAccess} method is called with the
 856      * {@code key} as its argument.
 857      * <p>
 858      * If there is no current set of system properties, a set of system
 859      * properties is first created and initialized in the same manner as
 860      * for the {@code getProperties} method.
 861      *
 862      * @param      key   the name of the system property.
 863      * @param      def   a default value.
 864      * @return     the string value of the system property,
 865      *             or the default value if there is no property with that key.
 866      *
 867      * @throws     SecurityException  if a security manager exists and its
 868      *             {@code checkPropertyAccess} method doesn't allow
 869      *             access to the specified system property.
 870      * @throws     NullPointerException if {@code key} is {@code null}.
 871      * @throws     IllegalArgumentException if {@code key} is empty.
 872      * @see        #setProperty
 873      * @see        java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
 874      * @see        java.lang.System#getProperties()
 875      */
 876     public static String getProperty(String key, String def) {
 877         checkKey(key);
 878         SecurityManager sm = getSecurityManager();
 879         if (sm != null) {
 880             sm.checkPropertyAccess(key);
 881         }
 882 
 883         return props.getProperty(key, def);
 884     }
 885 
 886     /**
 887      * Sets the system property indicated by the specified key.
 888      *
 889      * First, if a security manager exists, its
 890      * {@code SecurityManager.checkPermission} method
 891      * is called with a {@code PropertyPermission(key, "write")}
 892      * permission. This may result in a SecurityException being thrown.
 893      * If no exception is thrown, the specified property is set to the given
 894      * value.
 895      *
 896      * @apiNote
 897      * <strong>Changing a standard system property may have unpredictable results
 898      * unless otherwise specified</strong>.
 899      * See {@linkplain #getProperties getProperties} for details.
 900      *
 901      * @param      key   the name of the system property.
 902      * @param      value the value of the system property.
 903      * @return     the previous value of the system property,
 904      *             or {@code null} if it did not have one.
 905      *
 906      * @throws     SecurityException  if a security manager exists and its
 907      *             {@code checkPermission} method doesn't allow
 908      *             setting of the specified property.
 909      * @throws     NullPointerException if {@code key} or
 910      *             {@code value} is {@code null}.
 911      * @throws     IllegalArgumentException if {@code key} is empty.
 912      * @see        #getProperty
 913      * @see        java.lang.System#getProperty(java.lang.String)
 914      * @see        java.lang.System#getProperty(java.lang.String, java.lang.String)
 915      * @see        java.util.PropertyPermission
 916      * @see        SecurityManager#checkPermission
 917      * @since      1.2
 918      */
 919     public static String setProperty(String key, String value) {
 920         checkKey(key);
 921         SecurityManager sm = getSecurityManager();
 922         if (sm != null) {
 923             sm.checkPermission(new PropertyPermission(key,
 924                 SecurityConstants.PROPERTY_WRITE_ACTION));
 925         }
 926 
 927         return (String) props.setProperty(key, value);
 928     }
 929 
 930     /**
 931      * Removes the system property indicated by the specified key.
 932      *
 933      * First, if a security manager exists, its
 934      * {@code SecurityManager.checkPermission} method
 935      * is called with a {@code PropertyPermission(key, "write")}
 936      * permission. This may result in a SecurityException being thrown.
 937      * If no exception is thrown, the specified property is removed.
 938      *
 939      * @apiNote
 940      * <strong>Changing a standard system property may have unpredictable results
 941      * unless otherwise specified</strong>.
 942      * See {@linkplain #getProperties getProperties} method for details.
 943      *
 944      * @param      key   the name of the system property to be removed.
 945      * @return     the previous string value of the system property,
 946      *             or {@code null} if there was no property with that key.
 947      *
 948      * @throws     SecurityException  if a security manager exists and its
 949      *             {@code checkPropertyAccess} method doesn't allow
 950      *              access to the specified system property.
 951      * @throws     NullPointerException if {@code key} is {@code null}.
 952      * @throws     IllegalArgumentException if {@code key} is empty.
 953      * @see        #getProperty
 954      * @see        #setProperty
 955      * @see        java.util.Properties
 956      * @see        java.lang.SecurityException
 957      * @see        java.lang.SecurityManager#checkPropertiesAccess()
 958      * @since 1.5
 959      */
 960     public static String clearProperty(String key) {
 961         checkKey(key);
 962         SecurityManager sm = getSecurityManager();
 963         if (sm != null) {
 964             sm.checkPermission(new PropertyPermission(key, "write"));
 965         }
 966 
 967         return (String) props.remove(key);
 968     }
 969 
 970     private static void checkKey(String key) {
 971         if (key == null) {
 972             throw new NullPointerException("key can't be null");
 973         }
 974         if (key.isEmpty()) {
 975             throw new IllegalArgumentException("key can't be empty");
 976         }
 977     }
 978 
 979     /**
 980      * Gets the value of the specified environment variable. An
 981      * environment variable is a system-dependent external named
 982      * value.
 983      *
 984      * <p>If a security manager exists, its
 985      * {@link SecurityManager#checkPermission checkPermission}
 986      * method is called with a
 987      * {@link RuntimePermission RuntimePermission("getenv."+name)}
 988      * permission.  This may result in a {@link SecurityException}
 989      * being thrown.  If no exception is thrown the value of the
 990      * variable {@code name} is returned.
 991      *
 992      * <p><a id="EnvironmentVSSystemProperties"><i>System
 993      * properties</i> and <i>environment variables</i></a> are both
 994      * conceptually mappings between names and values.  Both
 995      * mechanisms can be used to pass user-defined information to a
 996      * Java process.  Environment variables have a more global effect,
 997      * because they are visible to all descendants of the process
 998      * which defines them, not just the immediate Java subprocess.
 999      * They can have subtly different semantics, such as case
1000      * insensitivity, on different operating systems.  For these
1001      * reasons, environment variables are more likely to have
1002      * unintended side effects.  It is best to use system properties
1003      * where possible.  Environment variables should be used when a
1004      * global effect is desired, or when an external system interface
1005      * requires an environment variable (such as {@code PATH}).
1006      *
1007      * <p>On UNIX systems the alphabetic case of {@code name} is
1008      * typically significant, while on Microsoft Windows systems it is
1009      * typically not.  For example, the expression
1010      * {@code System.getenv("FOO").equals(System.getenv("foo"))}
1011      * is likely to be true on Microsoft Windows.
1012      *
1013      * @param  name the name of the environment variable
1014      * @return the string value of the variable, or {@code null}
1015      *         if the variable is not defined in the system environment
1016      * @throws NullPointerException if {@code name} is {@code null}
1017      * @throws SecurityException
1018      *         if a security manager exists and its
1019      *         {@link SecurityManager#checkPermission checkPermission}
1020      *         method doesn't allow access to the environment variable
1021      *         {@code name}
1022      * @see    #getenv()
1023      * @see    ProcessBuilder#environment()
1024      */
1025     public static String getenv(String name) {
1026         SecurityManager sm = getSecurityManager();
1027         if (sm != null) {
1028             sm.checkPermission(new RuntimePermission("getenv."+name));
1029         }
1030 
1031         return ProcessEnvironment.getenv(name);
1032     }
1033 
1034 
1035     /**
1036      * Returns an unmodifiable string map view of the current system environment.
1037      * The environment is a system-dependent mapping from names to
1038      * values which is passed from parent to child processes.
1039      *
1040      * <p>If the system does not support environment variables, an
1041      * empty map is returned.
1042      *
1043      * <p>The returned map will never contain null keys or values.
1044      * Attempting to query the presence of a null key or value will
1045      * throw a {@link NullPointerException}.  Attempting to query
1046      * the presence of a key or value which is not of type
1047      * {@link String} will throw a {@link ClassCastException}.
1048      *
1049      * <p>The returned map and its collection views may not obey the
1050      * general contract of the {@link Object#equals} and
1051      * {@link Object#hashCode} methods.
1052      *
1053      * <p>The returned map is typically case-sensitive on all platforms.
1054      *
1055      * <p>If a security manager exists, its
1056      * {@link SecurityManager#checkPermission checkPermission}
1057      * method is called with a
1058      * {@link RuntimePermission RuntimePermission("getenv.*")} permission.
1059      * This may result in a {@link SecurityException} being thrown.
1060      *
1061      * <p>When passing information to a Java subprocess,
1062      * <a href=#EnvironmentVSSystemProperties>system properties</a>
1063      * are generally preferred over environment variables.
1064      *
1065      * @return the environment as a map of variable names to values
1066      * @throws SecurityException
1067      *         if a security manager exists and its
1068      *         {@link SecurityManager#checkPermission checkPermission}
1069      *         method doesn't allow access to the process environment
1070      * @see    #getenv(String)
1071      * @see    ProcessBuilder#environment()
1072      * @since  1.5
1073      */
1074     public static java.util.Map<String,String> getenv() {
1075         SecurityManager sm = getSecurityManager();
1076         if (sm != null) {
1077             sm.checkPermission(new RuntimePermission("getenv.*"));
1078         }
1079 
1080         return ProcessEnvironment.getenv();
1081     }
1082 
1083     /**
1084      * {@code System.Logger} instances log messages that will be
1085      * routed to the underlying logging framework the {@link System.LoggerFinder
1086      * LoggerFinder} uses.
1087      *
1088      * {@code System.Logger} instances are typically obtained from
1089      * the {@link java.lang.System System} class, by calling
1090      * {@link java.lang.System#getLogger(java.lang.String) System.getLogger(loggerName)}
1091      * or {@link java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle)
1092      * System.getLogger(loggerName, bundle)}.
1093      *
1094      * @see java.lang.System#getLogger(java.lang.String)
1095      * @see java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle)
1096      * @see java.lang.System.LoggerFinder
1097      *
1098      * @since 9
1099      */
1100     public interface Logger {
1101 
1102         /**
1103          * System {@linkplain Logger loggers} levels.
1104          *
1105          * A level has a {@linkplain #getName() name} and {@linkplain
1106          * #getSeverity() severity}.
1107          * Level values are {@link #ALL}, {@link #TRACE}, {@link #DEBUG},
1108          * {@link #INFO}, {@link #WARNING}, {@link #ERROR}, {@link #OFF},
1109          * by order of increasing severity.
1110          * <br>
1111          * {@link #ALL} and {@link #OFF}
1112          * are simple markers with severities mapped respectively to
1113          * {@link java.lang.Integer#MIN_VALUE Integer.MIN_VALUE} and
1114          * {@link java.lang.Integer#MAX_VALUE Integer.MAX_VALUE}.
1115          * <p>
1116          * <b>Severity values and Mapping to {@code java.util.logging.Level}.</b>
1117          * <p>
1118          * {@linkplain System.Logger.Level System logger levels} are mapped to
1119          * {@linkplain java.util.logging.Level  java.util.logging levels}
1120          * of corresponding severity.
1121          * <br>The mapping is as follows:
1122          * <br><br>
1123          * <table class="striped">
1124          * <caption>System.Logger Severity Level Mapping</caption>
1125          * <thead>
1126          * <tr><th scope="col">System.Logger Levels</th>
1127          *     <th scope="col">java.util.logging Levels</th>
1128          * </thead>
1129          * <tbody>
1130          * <tr><th scope="row">{@link Logger.Level#ALL ALL}</th>
1131          *     <td>{@link java.util.logging.Level#ALL ALL}</td>
1132          * <tr><th scope="row">{@link Logger.Level#TRACE TRACE}</th>
1133          *     <td>{@link java.util.logging.Level#FINER FINER}</td>
1134          * <tr><th scope="row">{@link Logger.Level#DEBUG DEBUG}</th>
1135          *     <td>{@link java.util.logging.Level#FINE FINE}</td>
1136          * <tr><th scope="row">{@link Logger.Level#INFO INFO}</th>
1137          *     <td>{@link java.util.logging.Level#INFO INFO}</td>
1138          * <tr><th scope="row">{@link Logger.Level#WARNING WARNING}</th>
1139          *     <td>{@link java.util.logging.Level#WARNING WARNING}</td>
1140          * <tr><th scope="row">{@link Logger.Level#ERROR ERROR}</th>
1141          *     <td>{@link java.util.logging.Level#SEVERE SEVERE}</td>
1142          * <tr><th scope="row">{@link Logger.Level#OFF OFF}</th>
1143          *     <td>{@link java.util.logging.Level#OFF OFF}</td>
1144          * </tbody>
1145          * </table>
1146          *
1147          * @since 9
1148          *
1149          * @see java.lang.System.LoggerFinder
1150          * @see java.lang.System.Logger
1151          */
1152         public enum Level {
1153 
1154             // for convenience, we're reusing java.util.logging.Level int values
1155             // the mapping logic in sun.util.logging.PlatformLogger depends
1156             // on this.
1157             /**
1158              * A marker to indicate that all levels are enabled.
1159              * This level {@linkplain #getSeverity() severity} is
1160              * {@link Integer#MIN_VALUE}.
1161              */
1162             ALL(Integer.MIN_VALUE),  // typically mapped to/from j.u.l.Level.ALL
1163             /**
1164              * {@code TRACE} level: usually used to log diagnostic information.
1165              * This level {@linkplain #getSeverity() severity} is
1166              * {@code 400}.
1167              */
1168             TRACE(400),   // typically mapped to/from j.u.l.Level.FINER
1169             /**
1170              * {@code DEBUG} level: usually used to log debug information traces.
1171              * This level {@linkplain #getSeverity() severity} is
1172              * {@code 500}.
1173              */
1174             DEBUG(500),   // typically mapped to/from j.u.l.Level.FINEST/FINE/CONFIG
1175             /**
1176              * {@code INFO} level: usually used to log information messages.
1177              * This level {@linkplain #getSeverity() severity} is
1178              * {@code 800}.
1179              */
1180             INFO(800),    // typically mapped to/from j.u.l.Level.INFO
1181             /**
1182              * {@code WARNING} level: usually used to log warning messages.
1183              * This level {@linkplain #getSeverity() severity} is
1184              * {@code 900}.
1185              */
1186             WARNING(900), // typically mapped to/from j.u.l.Level.WARNING
1187             /**
1188              * {@code ERROR} level: usually used to log error messages.
1189              * This level {@linkplain #getSeverity() severity} is
1190              * {@code 1000}.
1191              */
1192             ERROR(1000),  // typically mapped to/from j.u.l.Level.SEVERE
1193             /**
1194              * A marker to indicate that all levels are disabled.
1195              * This level {@linkplain #getSeverity() severity} is
1196              * {@link Integer#MAX_VALUE}.
1197              */
1198             OFF(Integer.MAX_VALUE);  // typically mapped to/from j.u.l.Level.OFF
1199 
1200             private final int severity;
1201 
1202             private Level(int severity) {
1203                 this.severity = severity;
1204             }
1205 
1206             /**
1207              * Returns the name of this level.
1208              * @return this level {@linkplain #name()}.
1209              */
1210             public final String getName() {
1211                 return name();
1212             }
1213 
1214             /**
1215              * Returns the severity of this level.
1216              * A higher severity means a more severe condition.
1217              * @return this level severity.
1218              */
1219             public final int getSeverity() {
1220                 return severity;
1221             }
1222         }
1223 
1224         /**
1225          * Returns the name of this logger.
1226          *
1227          * @return the logger name.
1228          */
1229         public String getName();
1230 
1231         /**
1232          * Checks if a message of the given level would be logged by
1233          * this logger.
1234          *
1235          * @param level the log message level.
1236          * @return {@code true} if the given log message level is currently
1237          *         being logged.
1238          *
1239          * @throws NullPointerException if {@code level} is {@code null}.
1240          */
1241         public boolean isLoggable(Level level);
1242 
1243         /**
1244          * Logs a message.
1245          *
1246          * @implSpec The default implementation for this method calls
1247          * {@code this.log(level, (ResourceBundle)null, msg, (Object[])null);}
1248          *
1249          * @param level the log message level.
1250          * @param msg the string message (or a key in the message catalog, if
1251          * this logger is a {@link
1252          * LoggerFinder#getLocalizedLogger(java.lang.String,
1253          * java.util.ResourceBundle, java.lang.Module) localized logger});
1254          * can be {@code null}.
1255          *
1256          * @throws NullPointerException if {@code level} is {@code null}.
1257          */
1258         public default void log(Level level, String msg) {
1259             log(level, (ResourceBundle) null, msg, (Object[]) null);
1260         }
1261 
1262         /**
1263          * Logs a lazily supplied message.
1264          *
1265          * If the logger is currently enabled for the given log message level
1266          * then a message is logged that is the result produced by the
1267          * given supplier function.  Otherwise, the supplier is not operated on.
1268          *
1269          * @implSpec When logging is enabled for the given level, the default
1270          * implementation for this method calls
1271          * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), (Object[])null);}
1272          *
1273          * @param level the log message level.
1274          * @param msgSupplier a supplier function that produces a message.
1275          *
1276          * @throws NullPointerException if {@code level} is {@code null},
1277          *         or {@code msgSupplier} is {@code null}.
1278          */
1279         public default void log(Level level, Supplier<String> msgSupplier) {
1280             Objects.requireNonNull(msgSupplier);
1281             if (isLoggable(Objects.requireNonNull(level))) {
1282                 log(level, (ResourceBundle) null, msgSupplier.get(), (Object[]) null);
1283             }
1284         }
1285 
1286         /**
1287          * Logs a message produced from the given object.
1288          *
1289          * If the logger is currently enabled for the given log message level then
1290          * a message is logged that, by default, is the result produced from
1291          * calling  toString on the given object.
1292          * Otherwise, the object is not operated on.
1293          *
1294          * @implSpec When logging is enabled for the given level, the default
1295          * implementation for this method calls
1296          * {@code this.log(level, (ResourceBundle)null, obj.toString(), (Object[])null);}
1297          *
1298          * @param level the log message level.
1299          * @param obj the object to log.
1300          *
1301          * @throws NullPointerException if {@code level} is {@code null}, or
1302          *         {@code obj} is {@code null}.
1303          */
1304         public default void log(Level level, Object obj) {
1305             Objects.requireNonNull(obj);
1306             if (isLoggable(Objects.requireNonNull(level))) {
1307                 this.log(level, (ResourceBundle) null, obj.toString(), (Object[]) null);
1308             }
1309         }
1310 
1311         /**
1312          * Logs a message associated with a given throwable.
1313          *
1314          * @implSpec The default implementation for this method calls
1315          * {@code this.log(level, (ResourceBundle)null, msg, thrown);}
1316          *
1317          * @param level the log message level.
1318          * @param msg the string message (or a key in the message catalog, if
1319          * this logger is a {@link
1320          * LoggerFinder#getLocalizedLogger(java.lang.String,
1321          * java.util.ResourceBundle, java.lang.Module) localized logger});
1322          * can be {@code null}.
1323          * @param thrown a {@code Throwable} associated with the log message;
1324          *        can be {@code null}.
1325          *
1326          * @throws NullPointerException if {@code level} is {@code null}.
1327          */
1328         public default void log(Level level, String msg, Throwable thrown) {
1329             this.log(level, null, msg, thrown);
1330         }
1331 
1332         /**
1333          * Logs a lazily supplied message associated with a given throwable.
1334          *
1335          * If the logger is currently enabled for the given log message level
1336          * then a message is logged that is the result produced by the
1337          * given supplier function.  Otherwise, the supplier is not operated on.
1338          *
1339          * @implSpec When logging is enabled for the given level, the default
1340          * implementation for this method calls
1341          * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), thrown);}
1342          *
1343          * @param level one of the log message level identifiers.
1344          * @param msgSupplier a supplier function that produces a message.
1345          * @param thrown a {@code Throwable} associated with log message;
1346          *               can be {@code null}.
1347          *
1348          * @throws NullPointerException if {@code level} is {@code null}, or
1349          *                               {@code msgSupplier} is {@code null}.
1350          */
1351         public default void log(Level level, Supplier<String> msgSupplier,
1352                 Throwable thrown) {
1353             Objects.requireNonNull(msgSupplier);
1354             if (isLoggable(Objects.requireNonNull(level))) {
1355                 this.log(level, null, msgSupplier.get(), thrown);
1356             }
1357         }
1358 
1359         /**
1360          * Logs a message with an optional list of parameters.
1361          *
1362          * @implSpec The default implementation for this method calls
1363          * {@code this.log(level, (ResourceBundle)null, format, params);}
1364          *
1365          * @param level one of the log message level identifiers.
1366          * @param format the string message format in {@link
1367          * java.text.MessageFormat} format, (or a key in the message
1368          * catalog, if this logger is a {@link
1369          * LoggerFinder#getLocalizedLogger(java.lang.String,
1370          * java.util.ResourceBundle, java.lang.Module) localized logger});
1371          * can be {@code null}.
1372          * @param params an optional list of parameters to the message (may be
1373          * none).
1374          *
1375          * @throws NullPointerException if {@code level} is {@code null}.
1376          */
1377         public default void log(Level level, String format, Object... params) {
1378             this.log(level, null, format, params);
1379         }
1380 
1381         /**
1382          * Logs a localized message associated with a given throwable.
1383          *
1384          * If the given resource bundle is non-{@code null},  the {@code msg}
1385          * string is localized using the given resource bundle.
1386          * Otherwise the {@code msg} string is not localized.
1387          *
1388          * @param level the log message level.
1389          * @param bundle a resource bundle to localize {@code msg}; can be
1390          * {@code null}.
1391          * @param msg the string message (or a key in the message catalog,
1392          *            if {@code bundle} is not {@code null}); can be {@code null}.
1393          * @param thrown a {@code Throwable} associated with the log message;
1394          *        can be {@code null}.
1395          *
1396          * @throws NullPointerException if {@code level} is {@code null}.
1397          */
1398         public void log(Level level, ResourceBundle bundle, String msg,
1399                 Throwable thrown);
1400 
1401         /**
1402          * Logs a message with resource bundle and an optional list of
1403          * parameters.
1404          *
1405          * If the given resource bundle is non-{@code null},  the {@code format}
1406          * string is localized using the given resource bundle.
1407          * Otherwise the {@code format} string is not localized.
1408          *
1409          * @param level the log message level.
1410          * @param bundle a resource bundle to localize {@code format}; can be
1411          * {@code null}.
1412          * @param format the string message format in {@link
1413          * java.text.MessageFormat} format, (or a key in the message
1414          * catalog if {@code bundle} is not {@code null}); can be {@code null}.
1415          * @param params an optional list of parameters to the message (may be
1416          * none).
1417          *
1418          * @throws NullPointerException if {@code level} is {@code null}.
1419          */
1420         public void log(Level level, ResourceBundle bundle, String format,
1421                 Object... params);
1422     }
1423 
1424     /**
1425      * The {@code LoggerFinder} service is responsible for creating, managing,
1426      * and configuring loggers to the underlying framework it uses.
1427      *
1428      * A logger finder is a concrete implementation of this class that has a
1429      * zero-argument constructor and implements the abstract methods defined
1430      * by this class.
1431      * The loggers returned from a logger finder are capable of routing log
1432      * messages to the logging backend this provider supports.
1433      * A given invocation of the Java Runtime maintains a single
1434      * system-wide LoggerFinder instance that is loaded as follows:
1435      * <ul>
1436      *    <li>First it finds any custom {@code LoggerFinder} provider
1437      *        using the {@link java.util.ServiceLoader} facility with the
1438      *        {@linkplain ClassLoader#getSystemClassLoader() system class
1439      *        loader}.</li>
1440      *    <li>If no {@code LoggerFinder} provider is found, the system default
1441      *        {@code LoggerFinder} implementation will be used.</li>
1442      * </ul>
1443      * <p>
1444      * An application can replace the logging backend
1445      * <i>even when the java.logging module is present</i>, by simply providing
1446      * and declaring an implementation of the {@link LoggerFinder} service.
1447      * <p>
1448      * <b>Default Implementation</b>
1449      * <p>
1450      * The system default {@code LoggerFinder} implementation uses
1451      * {@code java.util.logging} as the backend framework when the
1452      * {@code java.logging} module is present.
1453      * It returns a {@linkplain System.Logger logger} instance
1454      * that will route log messages to a {@link java.util.logging.Logger
1455      * java.util.logging.Logger}. Otherwise, if {@code java.logging} is not
1456      * present, the default implementation will return a simple logger
1457      * instance that will route log messages of {@code INFO} level and above to
1458      * the console ({@code System.err}).
1459      * <p>
1460      * <b>Logging Configuration</b>
1461      * <p>
1462      * {@linkplain Logger Logger} instances obtained from the
1463      * {@code LoggerFinder} factory methods are not directly configurable by
1464      * the application. Configuration is the responsibility of the underlying
1465      * logging backend, and usually requires using APIs specific to that backend.
1466      * <p>For the default {@code LoggerFinder} implementation
1467      * using {@code java.util.logging} as its backend, refer to
1468      * {@link java.util.logging java.util.logging} for logging configuration.
1469      * For the default {@code LoggerFinder} implementation returning simple loggers
1470      * when the {@code java.logging} module is absent, the configuration
1471      * is implementation dependent.
1472      * <p>
1473      * Usually an application that uses a logging framework will log messages
1474      * through a logger facade defined (or supported) by that framework.
1475      * Applications that wish to use an external framework should log
1476      * through the facade associated with that framework.
1477      * <p>
1478      * A system class that needs to log messages will typically obtain
1479      * a {@link System.Logger} instance to route messages to the logging
1480      * framework selected by the application.
1481      * <p>
1482      * Libraries and classes that only need loggers to produce log messages
1483      * should not attempt to configure loggers by themselves, as that
1484      * would make them dependent from a specific implementation of the
1485      * {@code LoggerFinder} service.
1486      * <p>
1487      * In addition, when a security manager is present, loggers provided to
1488      * system classes should not be directly configurable through the logging
1489      * backend without requiring permissions.
1490      * <br>
1491      * It is the responsibility of the provider of
1492      * the concrete {@code LoggerFinder} implementation to ensure that
1493      * these loggers are not configured by untrusted code without proper
1494      * permission checks, as configuration performed on such loggers usually
1495      * affects all applications in the same Java Runtime.
1496      * <p>
1497      * <b>Message Levels and Mapping to backend levels</b>
1498      * <p>
1499      * A logger finder is responsible for mapping from a {@code
1500      * System.Logger.Level} to a level supported by the logging backend it uses.
1501      * <br>The default LoggerFinder using {@code java.util.logging} as the backend
1502      * maps {@code System.Logger} levels to
1503      * {@linkplain java.util.logging.Level java.util.logging} levels
1504      * of corresponding severity - as described in {@link Logger.Level
1505      * Logger.Level}.
1506      *
1507      * @see java.lang.System
1508      * @see java.lang.System.Logger
1509      *
1510      * @since 9
1511      */
1512     public static abstract class LoggerFinder {
1513         /**
1514          * The {@code RuntimePermission("loggerFinder")} is
1515          * necessary to subclass and instantiate the {@code LoggerFinder} class,
1516          * as well as to obtain loggers from an instance of that class.
1517          */
1518         static final RuntimePermission LOGGERFINDER_PERMISSION =
1519                 new RuntimePermission("loggerFinder");
1520 
1521         /**
1522          * Creates a new instance of {@code LoggerFinder}.
1523          *
1524          * @implNote It is recommended that a {@code LoggerFinder} service
1525          *   implementation does not perform any heavy initialization in its
1526          *   constructor, in order to avoid possible risks of deadlock or class
1527          *   loading cycles during the instantiation of the service provider.
1528          *
1529          * @throws SecurityException if a security manager is present and its
1530          *         {@code checkPermission} method doesn't allow the
1531          *         {@code RuntimePermission("loggerFinder")}.
1532          */
1533         protected LoggerFinder() {
1534             this(checkPermission());
1535         }
1536 
1537         private LoggerFinder(Void unused) {
1538             // nothing to do.
1539         }
1540 
1541         private static Void checkPermission() {
1542             final SecurityManager sm = System.getSecurityManager();
1543             if (sm != null) {
1544                 sm.checkPermission(LOGGERFINDER_PERMISSION);
1545             }
1546             return null;
1547         }
1548 
1549         /**
1550          * Returns an instance of {@link Logger Logger}
1551          * for the given {@code module}.
1552          *
1553          * @param name the name of the logger.
1554          * @param module the module for which the logger is being requested.
1555          *
1556          * @return a {@link Logger logger} suitable for use within the given
1557          *         module.
1558          * @throws NullPointerException if {@code name} is {@code null} or
1559          *        {@code module} is {@code null}.
1560          * @throws SecurityException if a security manager is present and its
1561          *         {@code checkPermission} method doesn't allow the
1562          *         {@code RuntimePermission("loggerFinder")}.
1563          */
1564         public abstract Logger getLogger(String name, Module module);
1565 
1566         /**
1567          * Returns a localizable instance of {@link Logger Logger}
1568          * for the given {@code module}.
1569          * The returned logger will use the provided resource bundle for
1570          * message localization.
1571          *
1572          * @implSpec By default, this method calls {@link
1573          * #getLogger(java.lang.String, java.lang.Module)
1574          * this.getLogger(name, module)} to obtain a logger, then wraps that
1575          * logger in a {@link Logger} instance where all methods that do not
1576          * take a {@link ResourceBundle} as parameter are redirected to one
1577          * which does - passing the given {@code bundle} for
1578          * localization. So for instance, a call to {@link
1579          * Logger#log(Logger.Level, String) Logger.log(Level.INFO, msg)}
1580          * will end up as a call to {@link
1581          * Logger#log(Logger.Level, ResourceBundle, String, Object...)
1582          * Logger.log(Level.INFO, bundle, msg, (Object[])null)} on the wrapped
1583          * logger instance.
1584          * Note however that by default, string messages returned by {@link
1585          * java.util.function.Supplier Supplier&lt;String&gt;} will not be
1586          * localized, as it is assumed that such strings are messages which are
1587          * already constructed, rather than keys in a resource bundle.
1588          * <p>
1589          * An implementation of {@code LoggerFinder} may override this method,
1590          * for example, when the underlying logging backend provides its own
1591          * mechanism for localizing log messages, then such a
1592          * {@code LoggerFinder} would be free to return a logger
1593          * that makes direct use of the mechanism provided by the backend.
1594          *
1595          * @param name    the name of the logger.
1596          * @param bundle  a resource bundle; can be {@code null}.
1597          * @param module  the module for which the logger is being requested.
1598          * @return an instance of {@link Logger Logger}  which will use the
1599          * provided resource bundle for message localization.
1600          *
1601          * @throws NullPointerException if {@code name} is {@code null} or
1602          *         {@code module} is {@code null}.
1603          * @throws SecurityException if a security manager is present and its
1604          *         {@code checkPermission} method doesn't allow the
1605          *         {@code RuntimePermission("loggerFinder")}.
1606          */
1607         public Logger getLocalizedLogger(String name, ResourceBundle bundle,
1608                                          Module module) {
1609             return new LocalizedLoggerWrapper<>(getLogger(name, module), bundle);
1610         }
1611 
1612         /**
1613          * Returns the {@code LoggerFinder} instance. There is one
1614          * single system-wide {@code LoggerFinder} instance in
1615          * the Java Runtime.  See the class specification of how the
1616          * {@link LoggerFinder LoggerFinder} implementation is located and
1617          * loaded.
1618 
1619          * @return the {@link LoggerFinder LoggerFinder} instance.
1620          * @throws SecurityException if a security manager is present and its
1621          *         {@code checkPermission} method doesn't allow the
1622          *         {@code RuntimePermission("loggerFinder")}.
1623          */
1624         public static LoggerFinder getLoggerFinder() {
1625             final SecurityManager sm = System.getSecurityManager();
1626             if (sm != null) {
1627                 sm.checkPermission(LOGGERFINDER_PERMISSION);
1628             }
1629             return accessProvider();
1630         }
1631 
1632 
1633         private static volatile LoggerFinder service;
1634         static LoggerFinder accessProvider() {
1635             // We do not need to synchronize: LoggerFinderLoader will
1636             // always return the same instance, so if we don't have it,
1637             // just fetch it again.
1638             if (service == null) {
1639                 PrivilegedAction<LoggerFinder> pa =
1640                         () -> LoggerFinderLoader.getLoggerFinder();
1641                 service = AccessController.doPrivileged(pa, null,
1642                         LOGGERFINDER_PERMISSION);
1643             }
1644             return service;
1645         }
1646 
1647     }
1648 
1649 
1650     /**
1651      * Returns an instance of {@link Logger Logger} for the caller's
1652      * use.
1653      *
1654      * @implSpec
1655      * Instances returned by this method route messages to loggers
1656      * obtained by calling {@link LoggerFinder#getLogger(java.lang.String,
1657      * java.lang.Module) LoggerFinder.getLogger(name, module)}, where
1658      * {@code module} is the caller's module.
1659      * In cases where {@code System.getLogger} is called from a context where
1660      * there is no caller frame on the stack (e.g when called directly
1661      * from a JNI attached thread), {@code IllegalCallerException} is thrown.
1662      * To obtain a logger in such a context, use an auxiliary class that will
1663      * implicitly be identified as the caller, or use the system {@link
1664      * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead.
1665      * Note that doing the latter may eagerly initialize the underlying
1666      * logging system.
1667      *
1668      * @apiNote
1669      * This method may defer calling the {@link
1670      * LoggerFinder#getLogger(java.lang.String, java.lang.Module)
1671      * LoggerFinder.getLogger} method to create an actual logger supplied by
1672      * the logging backend, for instance, to allow loggers to be obtained during
1673      * the system initialization time.
1674      *
1675      * @param name the name of the logger.
1676      * @return an instance of {@link Logger} that can be used by the calling
1677      *         class.
1678      * @throws NullPointerException if {@code name} is {@code null}.
1679      * @throws IllegalCallerException if there is no Java caller frame on the
1680      *         stack.
1681      *
1682      * @since 9
1683      */
1684     @CallerSensitive
1685     public static Logger getLogger(String name) {
1686         Objects.requireNonNull(name);
1687         final Class<?> caller = Reflection.getCallerClass();
1688         if (caller == null) {
1689             throw new IllegalCallerException("no caller frame");
1690         }
1691         return LazyLoggers.getLogger(name, caller.getModule());
1692     }
1693 
1694     /**
1695      * Returns a localizable instance of {@link Logger
1696      * Logger} for the caller's use.
1697      * The returned logger will use the provided resource bundle for message
1698      * localization.
1699      *
1700      * @implSpec
1701      * The returned logger will perform message localization as specified
1702      * by {@link LoggerFinder#getLocalizedLogger(java.lang.String,
1703      * java.util.ResourceBundle, java.lang.Module)
1704      * LoggerFinder.getLocalizedLogger(name, bundle, module)}, where
1705      * {@code module} is the caller's module.
1706      * In cases where {@code System.getLogger} is called from a context where
1707      * there is no caller frame on the stack (e.g when called directly
1708      * from a JNI attached thread), {@code IllegalCallerException} is thrown.
1709      * To obtain a logger in such a context, use an auxiliary class that
1710      * will implicitly be identified as the caller, or use the system {@link
1711      * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead.
1712      * Note that doing the latter may eagerly initialize the underlying
1713      * logging system.
1714      *
1715      * @apiNote
1716      * This method is intended to be used after the system is fully initialized.
1717      * This method may trigger the immediate loading and initialization
1718      * of the {@link LoggerFinder} service, which may cause issues if the
1719      * Java Runtime is not ready to initialize the concrete service
1720      * implementation yet.
1721      * System classes which may be loaded early in the boot sequence and
1722      * need to log localized messages should create a logger using
1723      * {@link #getLogger(java.lang.String)} and then use the log methods that
1724      * take a resource bundle as parameter.
1725      *
1726      * @param name    the name of the logger.
1727      * @param bundle  a resource bundle.
1728      * @return an instance of {@link Logger} which will use the provided
1729      * resource bundle for message localization.
1730      * @throws NullPointerException if {@code name} is {@code null} or
1731      *         {@code bundle} is {@code null}.
1732      * @throws IllegalCallerException if there is no Java caller frame on the
1733      *         stack.
1734      *
1735      * @since 9
1736      */
1737     @CallerSensitive
1738     public static Logger getLogger(String name, ResourceBundle bundle) {
1739         final ResourceBundle rb = Objects.requireNonNull(bundle);
1740         Objects.requireNonNull(name);
1741         final Class<?> caller = Reflection.getCallerClass();
1742         if (caller == null) {
1743             throw new IllegalCallerException("no caller frame");
1744         }
1745         final SecurityManager sm = System.getSecurityManager();
1746         // We don't use LazyLoggers if a resource bundle is specified.
1747         // Bootstrap sensitive classes in the JDK do not use resource bundles
1748         // when logging. This could be revisited later, if it needs to.
1749         if (sm != null) {
1750             final PrivilegedAction<Logger> pa =
1751                     () -> LoggerFinder.accessProvider()
1752                             .getLocalizedLogger(name, rb, caller.getModule());
1753             return AccessController.doPrivileged(pa, null,
1754                                          LoggerFinder.LOGGERFINDER_PERMISSION);
1755         }
1756         return LoggerFinder.accessProvider()
1757                 .getLocalizedLogger(name, rb, caller.getModule());
1758     }
1759 
1760     /**
1761      * Terminates the currently running Java Virtual Machine. The
1762      * argument serves as a status code; by convention, a nonzero status
1763      * code indicates abnormal termination.
1764      * <p>
1765      * This method calls the {@code exit} method in class
1766      * {@code Runtime}. This method never returns normally.
1767      * <p>
1768      * The call {@code System.exit(n)} is effectively equivalent to
1769      * the call:
1770      * <blockquote><pre>
1771      * Runtime.getRuntime().exit(n)
1772      * </pre></blockquote>
1773      *
1774      * @param      status   exit status.
1775      * @throws  SecurityException
1776      *        if a security manager exists and its {@code checkExit}
1777      *        method doesn't allow exit with the specified status.
1778      * @see        java.lang.Runtime#exit(int)
1779      */
1780     public static void exit(int status) {
1781         Runtime.getRuntime().exit(status);
1782     }
1783 
1784     /**
1785      * Runs the garbage collector.
1786      *
1787      * Calling the {@code gc} method suggests that the Java Virtual
1788      * Machine expend effort toward recycling unused objects in order to
1789      * make the memory they currently occupy available for quick reuse.
1790      * When control returns from the method call, the Java Virtual
1791      * Machine has made a best effort to reclaim space from all discarded
1792      * objects.
1793      * <p>
1794      * The call {@code System.gc()} is effectively equivalent to the
1795      * call:
1796      * <blockquote><pre>
1797      * Runtime.getRuntime().gc()
1798      * </pre></blockquote>
1799      *
1800      * @see     java.lang.Runtime#gc()
1801      */
1802     public static void gc() {
1803         Runtime.getRuntime().gc();
1804     }
1805 
1806     /**
1807      * Runs the finalization methods of any objects pending finalization.
1808      *
1809      * Calling this method suggests that the Java Virtual Machine expend
1810      * effort toward running the {@code finalize} methods of objects
1811      * that have been found to be discarded but whose {@code finalize}
1812      * methods have not yet been run. When control returns from the
1813      * method call, the Java Virtual Machine has made a best effort to
1814      * complete all outstanding finalizations.
1815      * <p>
1816      * The call {@code System.runFinalization()} is effectively
1817      * equivalent to the call:
1818      * <blockquote><pre>
1819      * Runtime.getRuntime().runFinalization()
1820      * </pre></blockquote>
1821      *
1822      * @see     java.lang.Runtime#runFinalization()
1823      */
1824     public static void runFinalization() {
1825         Runtime.getRuntime().runFinalization();
1826     }
1827 
1828     /**
1829      * Loads the native library specified by the filename argument.  The filename
1830      * argument must be an absolute path name.
1831      *
1832      * If the filename argument, when stripped of any platform-specific library
1833      * prefix, path, and file extension, indicates a library whose name is,
1834      * for example, L, and a native library called L is statically linked
1835      * with the VM, then the JNI_OnLoad_L function exported by the library
1836      * is invoked rather than attempting to load a dynamic library.
1837      * A filename matching the argument does not have to exist in the
1838      * file system.
1839      * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>
1840      * for more details.
1841      *
1842      * Otherwise, the filename argument is mapped to a native library image in
1843      * an implementation-dependent manner.
1844      *
1845      * <p>
1846      * The call {@code System.load(name)} is effectively equivalent
1847      * to the call:
1848      * <blockquote><pre>
1849      * Runtime.getRuntime().load(name)
1850      * </pre></blockquote>
1851      *
1852      * @param      filename   the file to load.
1853      * @throws     SecurityException  if a security manager exists and its
1854      *             {@code checkLink} method doesn't allow
1855      *             loading of the specified dynamic library
1856      * @throws     UnsatisfiedLinkError  if either the filename is not an
1857      *             absolute path name, the native library is not statically
1858      *             linked with the VM, or the library cannot be mapped to
1859      *             a native library image by the host system.
1860      * @throws     NullPointerException if {@code filename} is {@code null}
1861      * @see        java.lang.Runtime#load(java.lang.String)
1862      * @see        java.lang.SecurityManager#checkLink(java.lang.String)
1863      */
1864     @CallerSensitive
1865     public static void load(String filename) {
1866         Runtime.getRuntime().load0(Reflection.getCallerClass(), filename);
1867     }
1868 
1869     /**
1870      * Loads the native library specified by the {@code libname}
1871      * argument.  The {@code libname} argument must not contain any platform
1872      * specific prefix, file extension or path. If a native library
1873      * called {@code libname} is statically linked with the VM, then the
1874      * JNI_OnLoad_{@code libname} function exported by the library is invoked.
1875      * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>
1876      * for more details.
1877      *
1878      * Otherwise, the libname argument is loaded from a system library
1879      * location and mapped to a native library image in an implementation-
1880      * dependent manner.
1881      * <p>
1882      * The call {@code System.loadLibrary(name)} is effectively
1883      * equivalent to the call
1884      * <blockquote><pre>
1885      * Runtime.getRuntime().loadLibrary(name)
1886      * </pre></blockquote>
1887      *
1888      * @param      libname   the name of the library.
1889      * @throws     SecurityException  if a security manager exists and its
1890      *             {@code checkLink} method doesn't allow
1891      *             loading of the specified dynamic library
1892      * @throws     UnsatisfiedLinkError if either the libname argument
1893      *             contains a file path, the native library is not statically
1894      *             linked with the VM,  or the library cannot be mapped to a
1895      *             native library image by the host system.
1896      * @throws     NullPointerException if {@code libname} is {@code null}
1897      * @see        java.lang.Runtime#loadLibrary(java.lang.String)
1898      * @see        java.lang.SecurityManager#checkLink(java.lang.String)
1899      */
1900     @CallerSensitive
1901     public static void loadLibrary(String libname) {
1902         Runtime.getRuntime().loadLibrary0(Reflection.getCallerClass(), libname);
1903     }
1904 
1905     /**
1906      * Maps a library name into a platform-specific string representing
1907      * a native library.
1908      *
1909      * @param      libname the name of the library.
1910      * @return     a platform-dependent native library name.
1911      * @throws     NullPointerException if {@code libname} is {@code null}
1912      * @see        java.lang.System#loadLibrary(java.lang.String)
1913      * @see        java.lang.ClassLoader#findLibrary(java.lang.String)
1914      * @since      1.2
1915      */
1916     public static native String mapLibraryName(String libname);
1917 
1918     /**
1919      * Create PrintStream for stdout/err based on encoding.
1920      */
1921     private static PrintStream newPrintStream(FileOutputStream fos, String enc) {
1922        if (enc != null) {
1923             try {
1924                 return new PrintStream(new BufferedOutputStream(fos, 128), true, enc);
1925             } catch (UnsupportedEncodingException uee) {}
1926         }
1927         return new PrintStream(new BufferedOutputStream(fos, 128), true);
1928     }
1929 
1930     /**
1931      * Logs an exception/error at initialization time to stdout or stderr.
1932      *
1933      * @param printToStderr to print to stderr rather than stdout
1934      * @param printStackTrace to print the stack trace
1935      * @param msg the message to print before the exception, can be {@code null}
1936      * @param e the exception or error
1937      */
1938     private static void logInitException(boolean printToStderr,
1939                                          boolean printStackTrace,
1940                                          String msg,
1941                                          Throwable e) {
1942         if (VM.initLevel() < 1) {
1943             throw new InternalError("system classes not initialized");
1944         }
1945         PrintStream log = (printToStderr) ? err : out;
1946         if (msg != null) {
1947             log.println(msg);
1948         }
1949         if (printStackTrace) {
1950             e.printStackTrace(log);
1951         } else {
1952             log.println(e);
1953             for (Throwable suppressed : e.getSuppressed()) {
1954                 log.println("Suppressed: " + suppressed);
1955             }
1956             Throwable cause = e.getCause();
1957             if (cause != null) {
1958                 log.println("Caused by: " + cause);
1959             }
1960         }
1961     }
1962 
1963     /**
1964      * Create the Properties object from a map - masking out system properties
1965      * that are not intended for public access.
1966      */
1967     private static Properties createProperties(Map<String, String> initialProps) {
1968         Properties properties = new Properties(initialProps.size());
1969         for (var entry : initialProps.entrySet()) {
1970             String prop = entry.getKey();
1971             switch (prop) {
1972                 // Do not add private system properties to the Properties
1973                 case "sun.nio.MaxDirectMemorySize":
1974                 case "sun.nio.PageAlignDirectMemory":
1975                     // used by java.lang.Integer.IntegerCache
1976                 case "java.lang.Integer.IntegerCache.high":
1977                     // used by sun.launcher.LauncherHelper
1978                 case "sun.java.launcher.diag":
1979                     // used by jdk.internal.loader.ClassLoaders
1980                 case "jdk.boot.class.path.append":
1981                     break;
1982                 default:
1983                     properties.put(prop, entry.getValue());
1984             }
1985         }
1986         return properties;
1987     }
1988 
1989     /**
1990      * Initialize the system class.  Called after thread initialization.
1991      */
1992     private static void initPhase1() {
1993         // VM might invoke JNU_NewStringPlatform() to set those encoding
1994         // sensitive properties (user.home, user.name, boot.class.path, etc.)
1995         // during "props" initialization.
1996         // The charset is initialized in System.c and does not depend on the Properties.
1997         Map<String, String> tempProps = SystemProps.initProperties();
1998         VersionProps.init(tempProps);
1999 
2000         // There are certain system configurations that may be controlled by
2001         // VM options such as the maximum amount of direct memory and
2002         // Integer cache size used to support the object identity semantics
2003         // of autoboxing.  Typically, the library will obtain these values
2004         // from the properties set by the VM.  If the properties are for
2005         // internal implementation use only, these properties should be
2006         // masked from the system properties.
2007         //
2008         // Save a private copy of the system properties object that
2009         // can only be accessed by the internal implementation.
2010         VM.saveProperties(tempProps);
2011         props = createProperties(tempProps);
2012 
2013         StaticProperty.javaHome();          // Load StaticProperty to cache the property values
2014 
2015         lineSeparator = props.getProperty("line.separator");
2016 
2017         FileInputStream fdIn = new FileInputStream(FileDescriptor.in);
2018         FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
2019         FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err);
2020         setIn0(new BufferedInputStream(fdIn));
2021         setOut0(newPrintStream(fdOut, props.getProperty("sun.stdout.encoding")));
2022         setErr0(newPrintStream(fdErr, props.getProperty("sun.stderr.encoding")));
2023 
2024         // Setup Java signal handlers for HUP, TERM, and INT (where available).
2025         Terminator.setup();
2026 
2027         // Initialize any miscellaneous operating system settings that need to be
2028         // set for the class libraries. Currently this is no-op everywhere except
2029         // for Windows where the process-wide error mode is set before the java.io
2030         // classes are used.
2031         VM.initializeOSEnvironment();
2032 
2033         // The main thread is not added to its thread group in the same
2034         // way as other threads; we must do it ourselves here.
2035         Thread current = Thread.currentThread();
2036         current.getThreadGroup().add(current);
2037 
2038         // register shared secrets
2039         setJavaLangAccess();
2040 
2041         // Subsystems that are invoked during initialization can invoke
2042         // VM.isBooted() in order to avoid doing things that should
2043         // wait until the VM is fully initialized. The initialization level
2044         // is incremented from 0 to 1 here to indicate the first phase of
2045         // initialization has completed.
2046         // IMPORTANT: Ensure that this remains the last initialization action!
2047         VM.initLevel(1);
2048     }
2049 
2050     // @see #initPhase2()
2051     static ModuleLayer bootLayer;
2052 
2053     /*
2054      * Invoked by VM.  Phase 2 module system initialization.
2055      * Only classes in java.base can be loaded in this phase.
2056      *
2057      * @param printToStderr print exceptions to stderr rather than stdout
2058      * @param printStackTrace print stack trace when exception occurs
2059      *
2060      * @return JNI_OK for success, JNI_ERR for failure
2061      */
2062     private static int initPhase2(boolean printToStderr, boolean printStackTrace) {
2063         try {
2064             bootLayer = ModuleBootstrap.boot();
2065         } catch (Exception | Error e) {
2066             logInitException(printToStderr, printStackTrace,
2067                              "Error occurred during initialization of boot layer", e);
2068             return -1; // JNI_ERR
2069         }
2070 
2071         // module system initialized
2072         VM.initLevel(2);
2073 
2074         return 0; // JNI_OK
2075     }
2076 
2077     /*
2078      * Invoked by VM.  Phase 3 is the final system initialization:
2079      * 1. set security manager
2080      * 2. set system class loader
2081      * 3. set TCCL
2082      *
2083      * This method must be called after the module system initialization.
2084      * The security manager and system class loader may be a custom class from
2085      * the application classpath or modulepath.
2086      */
2087     private static void initPhase3() {
2088         String smProp = System.getProperty("java.security.manager");
2089         if (smProp != null) {
2090             switch (smProp) {
2091                 case "disallow":
2092                     allowSecurityManager = NEVER;
2093                     break;
2094                 case "allow":
2095                     allowSecurityManager = MAYBE;
2096                     break;
2097                 case "":
2098                 case "default":
2099                     setSecurityManager(new SecurityManager());
2100                     allowSecurityManager = MAYBE;
2101                     break;
2102                 default:
2103                     try {
2104                         ClassLoader cl = ClassLoader.getBuiltinAppClassLoader();
2105                         Class<?> c = Class.forName(smProp, false, cl);
2106                         Constructor<?> ctor = c.getConstructor();
2107                         // Must be a public subclass of SecurityManager with
2108                         // a public no-arg constructor
2109                         if (!SecurityManager.class.isAssignableFrom(c) ||
2110                             !Modifier.isPublic(c.getModifiers()) ||
2111                             !Modifier.isPublic(ctor.getModifiers())) {
2112                             throw new Error("Could not create SecurityManager: "
2113                                              + ctor.toString());
2114                         }
2115                         // custom security manager may be in non-exported package
2116                         ctor.setAccessible(true);
2117                         SecurityManager sm = (SecurityManager) ctor.newInstance();
2118                         setSecurityManager(sm);
2119                     } catch (Exception e) {
2120                         throw new InternalError("Could not create SecurityManager", e);
2121                     }
2122                     allowSecurityManager = MAYBE;
2123             }
2124         } else {
2125             allowSecurityManager = MAYBE;
2126         }
2127 
2128         // initializing the system class loader
2129         VM.initLevel(3);
2130 
2131         // system class loader initialized
2132         ClassLoader scl = ClassLoader.initSystemClassLoader();
2133 
2134         // set TCCL
2135         Thread.currentThread().setContextClassLoader(scl);
2136 
2137         // system is fully initialized
2138         VM.initLevel(4);
2139     }
2140 
2141     private static void setJavaLangAccess() {
2142         // Allow privileged classes outside of java.lang
2143         SharedSecrets.setJavaLangAccess(new JavaLangAccess() {
2144             public List<Method> getDeclaredPublicMethods(Class<?> klass, String name, Class<?>... parameterTypes) {
2145                 return klass.getDeclaredPublicMethods(name, parameterTypes);
2146             }
2147             public jdk.internal.reflect.ConstantPool getConstantPool(Class<?> klass) {
2148                 return klass.getConstantPool();
2149             }
2150             public boolean casAnnotationType(Class<?> klass, AnnotationType oldType, AnnotationType newType) {
2151                 return klass.casAnnotationType(oldType, newType);
2152             }
2153             public AnnotationType getAnnotationType(Class<?> klass) {
2154                 return klass.getAnnotationType();
2155             }
2156             public Map<Class<? extends Annotation>, Annotation> getDeclaredAnnotationMap(Class<?> klass) {
2157                 return klass.getDeclaredAnnotationMap();
2158             }
2159             public byte[] getRawClassAnnotations(Class<?> klass) {
2160                 return klass.getRawAnnotations();
2161             }
2162             public byte[] getRawClassTypeAnnotations(Class<?> klass) {
2163                 return klass.getRawTypeAnnotations();
2164             }
2165             public byte[] getRawExecutableTypeAnnotations(Executable executable) {
2166                 return Class.getExecutableTypeAnnotationBytes(executable);
2167             }
2168             public <E extends Enum<E>>
2169             E[] getEnumConstantsShared(Class<E> klass) {
2170                 return klass.getEnumConstantsShared();
2171             }
2172             public void blockedOn(Interruptible b) {
2173                 Thread.blockedOn(b);
2174             }
2175             public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) {
2176                 Shutdown.add(slot, registerShutdownInProgress, hook);
2177             }
2178             public Thread newThreadWithAcc(Runnable target, AccessControlContext acc) {
2179                 return new Thread(target, acc);
2180             }
2181             @SuppressWarnings("deprecation")
2182             public void invokeFinalize(Object o) throws Throwable {
2183                 o.finalize();
2184             }
2185             public ConcurrentHashMap<?, ?> createOrGetClassLoaderValueMap(ClassLoader cl) {
2186                 return cl.createOrGetClassLoaderValueMap();
2187             }
2188             public Class<?> defineClass(ClassLoader loader, String name, byte[] b, ProtectionDomain pd, String source) {
2189                 return ClassLoader.defineClass1(loader, name, b, 0, b.length, pd, source);
2190             }
2191             public Class<?> defineClass(ClassLoader loader, Class<?> lookup, String name, byte[] b, ProtectionDomain pd,
2192                                         int flags, Object classData) {
2193                 return ClassLoader.defineClass0(loader, lookup, name, b, 0, b.length, pd, flags, classData);
2194             }
2195             public Class<?> findBootstrapClassOrNull(ClassLoader cl, String name) {
2196                 return cl.findBootstrapClassOrNull(name);
2197             }
2198             public Package definePackage(ClassLoader cl, String name, Module module) {
2199                 return cl.definePackage(name, module);
2200             }
2201             public String fastUUID(long lsb, long msb) {
2202                 return Long.fastUUID(lsb, msb);
2203             }
2204             public void addNonExportedPackages(ModuleLayer layer) {
2205                 SecurityManager.addNonExportedPackages(layer);
2206             }
2207             public void invalidatePackageAccessCache() {
2208                 SecurityManager.invalidatePackageAccessCache();
2209             }
2210             public Module defineModule(ClassLoader loader,
2211                                        ModuleDescriptor descriptor,
2212                                        URI uri) {
2213                 return new Module(null, loader, descriptor, uri);
2214             }
2215             public Module defineUnnamedModule(ClassLoader loader) {
2216                 return new Module(loader);
2217             }
2218             public void addReads(Module m1, Module m2) {
2219                 m1.implAddReads(m2);
2220             }
2221             public void addReadsAllUnnamed(Module m) {
2222                 m.implAddReadsAllUnnamed();
2223             }
2224             public void addExports(Module m, String pn, Module other) {
2225                 m.implAddExports(pn, other);
2226             }
2227             public void addExportsToAllUnnamed(Module m, String pn) {
2228                 m.implAddExportsToAllUnnamed(pn);
2229             }
2230             public void addOpens(Module m, String pn, Module other) {
2231                 m.implAddOpens(pn, other);
2232             }
2233             public void addOpensToAllUnnamed(Module m, String pn) {
2234                 m.implAddOpensToAllUnnamed(pn);
2235             }
2236             public void addOpensToAllUnnamed(Module m, Iterator<String> packages) {
2237                 m.implAddOpensToAllUnnamed(packages);
2238             }
2239             public void addUses(Module m, Class<?> service) {
2240                 m.implAddUses(service);
2241             }
2242             public boolean isReflectivelyExported(Module m, String pn, Module other) {
2243                 return m.isReflectivelyExported(pn, other);
2244             }
2245             public boolean isReflectivelyOpened(Module m, String pn, Module other) {
2246                 return m.isReflectivelyOpened(pn, other);
2247             }
2248             public ServicesCatalog getServicesCatalog(ModuleLayer layer) {
2249                 return layer.getServicesCatalog();
2250             }
2251             public Stream<ModuleLayer> layers(ModuleLayer layer) {
2252                 return layer.layers();
2253             }
2254             public Stream<ModuleLayer> layers(ClassLoader loader) {
2255                 return ModuleLayer.layers(loader);
2256             }
2257 
2258             public String newStringNoRepl(byte[] bytes, Charset cs) throws CharacterCodingException  {
2259                 return StringCoding.newStringNoRepl(bytes, cs);
2260             }
2261 
2262             public byte[] getBytesNoRepl(String s, Charset cs) throws CharacterCodingException {
2263                 return StringCoding.getBytesNoRepl(s, cs);
2264             }
2265 
2266             public String newStringUTF8NoRepl(byte[] bytes, int off, int len) {
2267                 return StringCoding.newStringUTF8NoRepl(bytes, off, len);
2268             }
2269 
2270             public byte[] getBytesUTF8NoRepl(String s) {
2271                 return StringCoding.getBytesUTF8NoRepl(s);
2272             }
2273 
2274             public void setCause(Throwable t, Throwable cause) {
2275                 t.setCause(cause);
2276             }
2277 
2278             public ProtectionDomain protectionDomain(Class<?> c) {
2279                 return c.protectionDomain();
2280             }
2281         });
2282     }
2283 }