1 /* 2 * Copyright (c) 1994, 2023, 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 26 package java.lang; 27 28 import jdk.internal.misc.Blocker; 29 import jdk.internal.vm.annotation.IntrinsicCandidate; 30 31 /** 32 * Class {@code Object} is the root of the class hierarchy. 33 * Every class has {@code Object} as a superclass. All objects, 34 * including arrays, implement the methods of this class. 35 * 36 * @see java.lang.Class 37 * @since 1.0 38 */ 39 public class Object { 40 41 /** 42 * Constructs a new object. 43 */ 44 @IntrinsicCandidate 45 public Object() {} 46 47 /** 48 * Returns the runtime class of this {@code Object}. The returned 49 * {@code Class} object is the object that is locked by {@code 50 * static synchronized} methods of the represented class. 51 * 52 * <p><b>The actual result type is {@code Class<? extends |X|>} 53 * where {@code |X|} is the erasure of the static type of the 54 * expression on which {@code getClass} is called.</b> For 55 * example, no cast is required in this code fragment:</p> 56 * 57 * <p> 58 * {@code Number n = 0; }<br> 59 * {@code Class<? extends Number> c = n.getClass(); } 60 * </p> 61 * 62 * @return The {@code Class} object that represents the runtime 63 * class of this object. 64 * @jls 15.8.2 Class Literals 65 */ 66 @IntrinsicCandidate 67 public final native Class<?> getClass(); 68 69 /** 70 * {@return a hash code value for this object} This method is 71 * supported for the benefit of hash tables such as those provided by 72 * {@link java.util.HashMap}. 73 * <p> 74 * The general contract of {@code hashCode} is: 75 * <ul> 76 * <li>Whenever it is invoked on the same object more than once during 77 * an execution of a Java application, the {@code hashCode} method 78 * must consistently return the same integer, provided no information 79 * used in {@code equals} comparisons on the object is modified. 80 * This integer need not remain consistent from one execution of an 81 * application to another execution of the same application. 82 * <li>If two objects are equal according to the {@link 83 * #equals(Object) equals} method, then calling the {@code 84 * hashCode} method on each of the two objects must produce the 85 * same integer result. 86 * <li>It is <em>not</em> required that if two objects are unequal 87 * according to the {@link #equals(Object) equals} method, then 88 * calling the {@code hashCode} method on each of the two objects 89 * must produce distinct integer results. However, the programmer 90 * should be aware that producing distinct integer results for 91 * unequal objects may improve the performance of hash tables. 92 * </ul> 93 * 94 * @implSpec 95 * As far as is reasonably practical, the {@code hashCode} method defined 96 * by class {@code Object} returns distinct integers for distinct objects. 97 * 98 * @apiNote 99 * The {@link java.util.Objects#hash(Object...) hash} and {@link 100 * java.util.Objects#hashCode(Object) hashCode} methods of {@link 101 * java.util.Objects} can be used to help construct simple hash codes. 102 * 103 * @see java.lang.Object#equals(java.lang.Object) 104 * @see java.lang.System#identityHashCode 105 */ 106 @IntrinsicCandidate 107 public native int hashCode(); 108 109 /** 110 * Indicates whether some other object is "equal to" this one. 111 * <p> 112 * The {@code equals} method implements an equivalence relation 113 * on non-null object references: 114 * <ul> 115 * <li>It is <i>reflexive</i>: for any non-null reference value 116 * {@code x}, {@code x.equals(x)} should return 117 * {@code true}. 118 * <li>It is <i>symmetric</i>: for any non-null reference values 119 * {@code x} and {@code y}, {@code x.equals(y)} 120 * should return {@code true} if and only if 121 * {@code y.equals(x)} returns {@code true}. 122 * <li>It is <i>transitive</i>: for any non-null reference values 123 * {@code x}, {@code y}, and {@code z}, if 124 * {@code x.equals(y)} returns {@code true} and 125 * {@code y.equals(z)} returns {@code true}, then 126 * {@code x.equals(z)} should return {@code true}. 127 * <li>It is <i>consistent</i>: for any non-null reference values 128 * {@code x} and {@code y}, multiple invocations of 129 * {@code x.equals(y)} consistently return {@code true} 130 * or consistently return {@code false}, provided no 131 * information used in {@code equals} comparisons on the 132 * objects is modified. 133 * <li>For any non-null reference value {@code x}, 134 * {@code x.equals(null)} should return {@code false}. 135 * </ul> 136 * 137 * <p> 138 * An equivalence relation partitions the elements it operates on 139 * into <i>equivalence classes</i>; all the members of an 140 * equivalence class are equal to each other. Members of an 141 * equivalence class are substitutable for each other, at least 142 * for some purposes. 143 * 144 * @implSpec 145 * The {@code equals} method for class {@code Object} implements 146 * the most discriminating possible equivalence relation on objects; 147 * that is, for any non-null reference values {@code x} and 148 * {@code y}, this method returns {@code true} if and only 149 * if {@code x} and {@code y} refer to the same object 150 * ({@code x == y} has the value {@code true}). 151 * 152 * In other words, under the reference equality equivalence 153 * relation, each equivalence class only has a single element. 154 * 155 * @apiNote 156 * It is generally necessary to override the {@link #hashCode() hashCode} 157 * method whenever this method is overridden, so as to maintain the 158 * general contract for the {@code hashCode} method, which states 159 * that equal objects must have equal hash codes. 160 * <p>The two-argument {@link java.util.Objects#equals(Object, 161 * Object) Objects.equals} method implements an equivalence relation 162 * on two possibly-null object references. 163 * 164 * @param obj the reference object with which to compare. 165 * @return {@code true} if this object is the same as the obj 166 * argument; {@code false} otherwise. 167 * @see #hashCode() 168 * @see java.util.HashMap 169 */ 170 public boolean equals(Object obj) { 171 return (this == obj); 172 } 173 174 /** 175 * Creates and returns a copy of this object. The precise meaning 176 * of "copy" may depend on the class of the object. The general 177 * intent is that, for any object {@code x}, the expression: 178 * <blockquote> 179 * <pre> 180 * x.clone() != x</pre></blockquote> 181 * will be true, and that the expression: 182 * <blockquote> 183 * <pre> 184 * x.clone().getClass() == x.getClass()</pre></blockquote> 185 * will be {@code true}, but these are not absolute requirements. 186 * While it is typically the case that: 187 * <blockquote> 188 * <pre> 189 * x.clone().equals(x)</pre></blockquote> 190 * will be {@code true}, this is not an absolute requirement. 191 * <p> 192 * By convention, the returned object should be obtained by calling 193 * {@code super.clone}. If a class and all of its superclasses (except 194 * {@code Object}) obey this convention, it will be the case that 195 * {@code x.clone().getClass() == x.getClass()}. 196 * <p> 197 * By convention, the object returned by this method should be independent 198 * of this object (which is being cloned). To achieve this independence, 199 * it may be necessary to modify one or more fields of the object returned 200 * by {@code super.clone} before returning it. Typically, this means 201 * copying any mutable objects that comprise the internal "deep structure" 202 * of the object being cloned and replacing the references to these 203 * objects with references to the copies. If a class contains only 204 * primitive fields or references to immutable objects, then it is usually 205 * the case that no fields in the object returned by {@code super.clone} 206 * need to be modified. 207 * 208 * @implSpec 209 * The method {@code clone} for class {@code Object} performs a 210 * specific cloning operation. First, if the class of this object does 211 * not implement the interface {@code Cloneable}, then a 212 * {@code CloneNotSupportedException} is thrown. Note that all arrays 213 * are considered to implement the interface {@code Cloneable} and that 214 * the return type of the {@code clone} method of an array type {@code T[]} 215 * is {@code T[]} where T is any reference or primitive type. 216 * Otherwise, this method creates a new instance of the class of this 217 * object and initializes all its fields with exactly the contents of 218 * the corresponding fields of this object, as if by assignment; the 219 * contents of the fields are not themselves cloned. Thus, this method 220 * performs a "shallow copy" of this object, not a "deep copy" operation. 221 * <p> 222 * The class {@code Object} does not itself implement the interface 223 * {@code Cloneable}, so calling the {@code clone} method on an object 224 * whose class is {@code Object} will result in throwing an 225 * exception at run time. 226 * 227 * @return a clone of this instance. 228 * @throws CloneNotSupportedException if the object's class does not 229 * support the {@code Cloneable} interface. Subclasses 230 * that override the {@code clone} method can also 231 * throw this exception to indicate that an instance cannot 232 * be cloned. 233 * @see java.lang.Cloneable 234 */ 235 @IntrinsicCandidate 236 protected native Object clone() throws CloneNotSupportedException; 237 238 /** 239 * {@return a string representation of the object} 240 * @apiNote 241 * In general, the 242 * {@code toString} method returns a string that 243 * "textually represents" this object. The result should 244 * be a concise but informative representation that is easy for a 245 * person to read. 246 * It is recommended that all subclasses override this method. 247 * The string output is not necessarily stable over time or across 248 * JVM invocations. 249 * @implSpec 250 * The {@code toString} method for class {@code Object} 251 * returns a string consisting of the name of the class of which the 252 * object is an instance, the at-sign character `{@code @}', and 253 * the unsigned hexadecimal representation of the hash code of the 254 * object. In other words, this method returns a string equal to the 255 * value of: 256 * {@snippet lang=java : 257 * getClass().getName() + '@' + Integer.toHexString(hashCode()) 258 * } 259 * The {@link java.util.Objects#toIdentityString(Object) 260 * Objects.toIdentityString} method returns the string for an 261 * object equal to the string that would be returned if neither 262 * the {@code toString} nor {@code hashCode} methods were 263 * overridden by the object's class. 264 */ 265 public String toString() { 266 return getClass().getName() + "@" + Integer.toHexString(hashCode()); 267 } 268 269 /** 270 * Wakes up a single thread that is waiting on this object's 271 * monitor. If any threads are waiting on this object, one of them 272 * is chosen to be awakened. The choice is arbitrary and occurs at 273 * the discretion of the implementation. A thread waits on an object's 274 * monitor by calling one of the {@code wait} methods. 275 * <p> 276 * The awakened thread will not be able to proceed until the current 277 * thread relinquishes the lock on this object. The awakened thread will 278 * compete in the usual manner with any other threads that might be 279 * actively competing to synchronize on this object; for example, the 280 * awakened thread enjoys no reliable privilege or disadvantage in being 281 * the next thread to lock this object. 282 * <p> 283 * This method should only be called by a thread that is the owner 284 * of this object's monitor. A thread becomes the owner of the 285 * object's monitor in one of three ways: 286 * <ul> 287 * <li>By executing a synchronized instance method of that object. 288 * <li>By executing the body of a {@code synchronized} statement 289 * that synchronizes on the object. 290 * <li>For objects of type {@code Class,} by executing a 291 * static synchronized method of that class. 292 * </ul> 293 * <p> 294 * Only one thread at a time can own an object's monitor. 295 * 296 * @throws IllegalMonitorStateException if the current thread is not 297 * the owner of this object's monitor. 298 * @see java.lang.Object#notifyAll() 299 * @see java.lang.Object#wait() 300 */ 301 @IntrinsicCandidate 302 public final native void notify(); 303 304 /** 305 * Wakes up all threads that are waiting on this object's monitor. A 306 * thread waits on an object's monitor by calling one of the 307 * {@code wait} methods. 308 * <p> 309 * The awakened threads will not be able to proceed until the current 310 * thread relinquishes the lock on this object. The awakened threads 311 * will compete in the usual manner with any other threads that might 312 * be actively competing to synchronize on this object; for example, 313 * the awakened threads enjoy no reliable privilege or disadvantage in 314 * being the next thread to lock this object. 315 * <p> 316 * This method should only be called by a thread that is the owner 317 * of this object's monitor. See the {@code notify} method for a 318 * description of the ways in which a thread can become the owner of 319 * a monitor. 320 * 321 * @throws IllegalMonitorStateException if the current thread is not 322 * the owner of this object's monitor. 323 * @see java.lang.Object#notify() 324 * @see java.lang.Object#wait() 325 */ 326 @IntrinsicCandidate 327 public final native void notifyAll(); 328 329 /** 330 * Causes the current thread to wait until it is awakened, typically 331 * by being <em>notified</em> or <em>interrupted</em>. 332 * <p> 333 * In all respects, this method behaves as if {@code wait(0L, 0)} 334 * had been called. See the specification of the {@link #wait(long, int)} method 335 * for details. 336 * 337 * @throws IllegalMonitorStateException if the current thread is not 338 * the owner of the object's monitor 339 * @throws InterruptedException if any thread interrupted the current thread before or 340 * while the current thread was waiting. The <em>interrupted status</em> of the 341 * current thread is cleared when this exception is thrown. 342 * @see #notify() 343 * @see #notifyAll() 344 * @see #wait(long) 345 * @see #wait(long, int) 346 */ 347 public final void wait() throws InterruptedException { 348 wait(0L); 349 } 350 351 /** 352 * Causes the current thread to wait until it is awakened, typically 353 * by being <em>notified</em> or <em>interrupted</em>, or until a 354 * certain amount of real time has elapsed. 355 * <p> 356 * In all respects, this method behaves as if {@code wait(timeoutMillis, 0)} 357 * had been called. See the specification of the {@link #wait(long, int)} method 358 * for details. 359 * 360 * @param timeoutMillis the maximum time to wait, in milliseconds 361 * @throws IllegalArgumentException if {@code timeoutMillis} is negative 362 * @throws IllegalMonitorStateException if the current thread is not 363 * the owner of the object's monitor 364 * @throws InterruptedException if any thread interrupted the current thread before or 365 * while the current thread was waiting. The <em>interrupted status</em> of the 366 * current thread is cleared when this exception is thrown. 367 * @see #notify() 368 * @see #notifyAll() 369 * @see #wait() 370 * @see #wait(long, int) 371 */ 372 public final void wait(long timeoutMillis) throws InterruptedException { 373 long comp = Blocker.begin(); 374 try { 375 wait0(timeoutMillis); 376 } catch (InterruptedException e) { 377 Thread thread = Thread.currentThread(); 378 if (thread.isVirtual()) 379 thread.getAndClearInterrupt(); 380 throw e; 381 } finally { 382 Blocker.end(comp); 383 } 384 } 385 386 // final modifier so method not in vtable 387 private final native void wait0(long timeoutMillis) throws InterruptedException; 388 389 /** 390 * Causes the current thread to wait until it is awakened, typically 391 * by being <em>notified</em> or <em>interrupted</em>, or until a 392 * certain amount of real time has elapsed. 393 * <p> 394 * The current thread must own this object's monitor lock. See the 395 * {@link #notify notify} method for a description of the ways in which 396 * a thread can become the owner of a monitor lock. 397 * <p> 398 * This method causes the current thread (referred to here as <var>T</var>) to 399 * place itself in the wait set for this object and then to relinquish any 400 * and all synchronization claims on this object. Note that only the locks 401 * on this object are relinquished; any other objects on which the current 402 * thread may be synchronized remain locked while the thread waits. 403 * <p> 404 * Thread <var>T</var> then becomes disabled for thread scheduling purposes 405 * and lies dormant until one of the following occurs: 406 * <ul> 407 * <li>Some other thread invokes the {@code notify} method for this 408 * object and thread <var>T</var> happens to be arbitrarily chosen as 409 * the thread to be awakened. 410 * <li>Some other thread invokes the {@code notifyAll} method for this 411 * object. 412 * <li>Some other thread {@linkplain Thread#interrupt() interrupts} 413 * thread <var>T</var>. 414 * <li>The specified amount of real time has elapsed, more or less. 415 * The amount of real time, in nanoseconds, is given by the expression 416 * {@code 1000000 * timeoutMillis + nanos}. If {@code timeoutMillis} and {@code nanos} 417 * are both zero, then real time is not taken into consideration and the 418 * thread waits until awakened by one of the other causes. 419 * <li>Thread <var>T</var> is awakened spuriously. (See below.) 420 * </ul> 421 * <p> 422 * The thread <var>T</var> is then removed from the wait set for this 423 * object and re-enabled for thread scheduling. It competes in the 424 * usual manner with other threads for the right to synchronize on the 425 * object; once it has regained control of the object, all its 426 * synchronization claims on the object are restored to the status quo 427 * ante - that is, to the situation as of the time that the {@code wait} 428 * method was invoked. Thread <var>T</var> then returns from the 429 * invocation of the {@code wait} method. Thus, on return from the 430 * {@code wait} method, the synchronization state of the object and of 431 * thread {@code T} is exactly as it was when the {@code wait} method 432 * was invoked. 433 * <p> 434 * A thread can wake up without being notified, interrupted, or timing out, a 435 * so-called <em>spurious wakeup</em>. While this will rarely occur in practice, 436 * applications must guard against it by testing for the condition that should 437 * have caused the thread to be awakened, and continuing to wait if the condition 438 * is not satisfied. See the example below. 439 * <p> 440 * For more information on this topic, see section 14.2, 441 * "Condition Queues," in Brian Goetz and others' <cite>Java Concurrency 442 * in Practice</cite> (Addison-Wesley, 2006) or Item 81 in Joshua 443 * Bloch's <cite>Effective Java, Third Edition</cite> (Addison-Wesley, 444 * 2018). 445 * <p> 446 * If the current thread is {@linkplain java.lang.Thread#interrupt() interrupted} 447 * by any thread before or while it is waiting, then an {@code InterruptedException} 448 * is thrown. The <em>interrupted status</em> of the current thread is cleared when 449 * this exception is thrown. This exception is not thrown until the lock status of 450 * this object has been restored as described above. 451 * 452 * @apiNote 453 * The recommended approach to waiting is to check the condition being awaited in 454 * a {@code while} loop around the call to {@code wait}, as shown in the example 455 * below. Among other things, this approach avoids problems that can be caused 456 * by spurious wakeups. 457 * 458 * {@snippet lang=java : 459 * synchronized (obj) { 460 * while ( <condition does not hold and timeout not exceeded> ) { 461 * long timeoutMillis = ... ; // recompute timeout values 462 * int nanos = ... ; 463 * obj.wait(timeoutMillis, nanos); 464 * } 465 * ... // Perform action appropriate to condition or timeout 466 * } 467 * } 468 * 469 * @param timeoutMillis the maximum time to wait, in milliseconds 470 * @param nanos additional time, in nanoseconds, in the range 0-999999 inclusive 471 * @throws IllegalArgumentException if {@code timeoutMillis} is negative, 472 * or if the value of {@code nanos} is out of range 473 * @throws IllegalMonitorStateException if the current thread is not 474 * the owner of the object's monitor 475 * @throws InterruptedException if any thread interrupted the current thread before or 476 * while the current thread was waiting. The <em>interrupted status</em> of the 477 * current thread is cleared when this exception is thrown. 478 * @see #notify() 479 * @see #notifyAll() 480 * @see #wait() 481 * @see #wait(long) 482 */ 483 public final void wait(long timeoutMillis, int nanos) throws InterruptedException { 484 if (timeoutMillis < 0) { 485 throw new IllegalArgumentException("timeoutMillis value is negative"); 486 } 487 488 if (nanos < 0 || nanos > 999999) { 489 throw new IllegalArgumentException( 490 "nanosecond timeout value out of range"); 491 } 492 493 if (nanos > 0 && timeoutMillis < Long.MAX_VALUE) { 494 timeoutMillis++; 495 } 496 497 wait(timeoutMillis); 498 } 499 500 /** 501 * Called by the garbage collector on an object when garbage collection 502 * determines that there are no more references to the object. 503 * A subclass overrides the {@code finalize} method to dispose of 504 * system resources or to perform other cleanup. 505 * <p> 506 * <b>When running in a Java virtual machine in which finalization has been 507 * disabled or removed, the garbage collector will never call 508 * {@code finalize()}. In a Java virtual machine in which finalization is 509 * enabled, the garbage collector might call {@code finalize} only after an 510 * indefinite delay.</b> 511 * <p> 512 * The general contract of {@code finalize} is that it is invoked 513 * if and when the Java virtual 514 * machine has determined that there is no longer any 515 * means by which this object can be accessed by any thread that has 516 * not yet died, except as a result of an action taken by the 517 * finalization of some other object or class which is ready to be 518 * finalized. The {@code finalize} method may take any action, including 519 * making this object available again to other threads; the usual purpose 520 * of {@code finalize}, however, is to perform cleanup actions before 521 * the object is irrevocably discarded. For example, the finalize method 522 * for an object that represents an input/output connection might perform 523 * explicit I/O transactions to break the connection before the object is 524 * permanently discarded. 525 * <p> 526 * The {@code finalize} method of class {@code Object} performs no 527 * special action; it simply returns normally. Subclasses of 528 * {@code Object} may override this definition. 529 * <p> 530 * The Java programming language does not guarantee which thread will 531 * invoke the {@code finalize} method for any given object. It is 532 * guaranteed, however, that the thread that invokes finalize will not 533 * be holding any user-visible synchronization locks when finalize is 534 * invoked. If an uncaught exception is thrown by the finalize method, 535 * the exception is ignored and finalization of that object terminates. 536 * <p> 537 * After the {@code finalize} method has been invoked for an object, no 538 * further action is taken until the Java virtual machine has again 539 * determined that there is no longer any means by which this object can 540 * be accessed by any thread that has not yet died, including possible 541 * actions by other objects or classes which are ready to be finalized, 542 * at which point the object may be discarded. 543 * <p> 544 * The {@code finalize} method is never invoked more than once by a Java 545 * virtual machine for any given object. 546 * <p> 547 * Any exception thrown by the {@code finalize} method causes 548 * the finalization of this object to be halted, but is otherwise 549 * ignored. 550 * 551 * @apiNote 552 * Classes that embed non-heap resources have many options 553 * for cleanup of those resources. The class must ensure that the 554 * lifetime of each instance is longer than that of any resource it embeds. 555 * {@link java.lang.ref.Reference#reachabilityFence} can be used to ensure that 556 * objects remain reachable while resources embedded in the object are in use. 557 * <p> 558 * A subclass should avoid overriding the {@code finalize} method 559 * unless the subclass embeds non-heap resources that must be cleaned up 560 * before the instance is collected. 561 * Finalizer invocations are not automatically chained, unlike constructors. 562 * If a subclass overrides {@code finalize} it must invoke the superclass 563 * finalizer explicitly. 564 * To guard against exceptions prematurely terminating the finalize chain, 565 * the subclass should use a {@code try-finally} block to ensure 566 * {@code super.finalize()} is always invoked. For example, 567 * {@snippet lang="java": 568 * @Override 569 * protected void finalize() throws Throwable { 570 * try { 571 * ... // cleanup subclass state 572 * } finally { 573 * super.finalize(); 574 * } 575 * } 576 * } 577 * 578 * @deprecated Finalization is deprecated and subject to removal in a future 579 * release. The use of finalization can lead to problems with security, 580 * performance, and reliability. 581 * See <a href="https://openjdk.org/jeps/421">JEP 421</a> for 582 * discussion and alternatives. 583 * <p> 584 * Subclasses that override {@code finalize} to perform cleanup should use 585 * alternative cleanup mechanisms and remove the {@code finalize} method. 586 * Use {@link java.lang.ref.Cleaner} and 587 * {@link java.lang.ref.PhantomReference} as safer ways to release resources 588 * when an object becomes unreachable. Alternatively, add a {@code close} 589 * method to explicitly release resources, and implement 590 * {@code AutoCloseable} to enable use of the {@code try}-with-resources 591 * statement. 592 * <p> 593 * This method will remain in place until finalizers have been removed from 594 * most existing code. 595 * 596 * @throws Throwable the {@code Exception} raised by this method 597 * @see java.lang.ref.WeakReference 598 * @see java.lang.ref.PhantomReference 599 * @jls 12.6 Finalization of Class Instances 600 */ 601 @Deprecated(since="9", forRemoval=true) 602 protected void finalize() throws Throwable { } 603 }