1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * Copyright (c) 1994, 2012, Oracle and/or its affiliates. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. Oracle designates this 9 * particular file as subject to the "Classpath" exception as provided 10 * by Oracle in the LICENSE file that accompanied this code. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 23 * or visit www.oracle.com if you need additional information or have any 24 * questions. 25 */ 26 27 package java.lang; 28 29 import dalvik.annotation.optimization.FastNative; 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 * @author unascribed 37 * @see java.lang.Class 38 * @since JDK1.0 39 */ 40 public class Object { 41 42 // Android-removed: registerNatives() not used on Android 43 // private static native void registerNatives(); 44 // static { 45 // registerNatives(); 46 // } 47 48 // Android-added: Use Android specific fields for Class and monitor. 49 private transient Class<?> shadow$_klass_; 50 private transient int shadow$_monitor_; 51 52 /** 53 * Returns the runtime class of this {@code Object}. The returned 54 * {@code Class} object is the object that is locked by {@code 55 * static synchronized} methods of the represented class. 56 * 57 * <p><b>The actual result type is {@code Class<? extends |X|>} 58 * where {@code |X|} is the erasure of the static type of the 59 * expression on which {@code getClass} is called.</b> For 60 * example, no cast is required in this code fragment:</p> 61 * 62 * <p> 63 * {@code Number n = 0; }<br> 64 * {@code Class<? extends Number> c = n.getClass(); } 65 * </p> 66 * 67 * @return The {@code Class} object that represents the runtime 68 * class of this object. 69 * @jls 15.8.2 Class Literals 70 */ 71 // Android-changed: Use Android specific fields for Class and monitor. 72 // public final native Class<?> getClass(); getClass()73 public final Class<?> getClass() { 74 return shadow$_klass_; 75 } 76 77 /** 78 * Returns a hash code value for the object. This method is 79 * supported for the benefit of hash tables such as those provided by 80 * {@link java.util.HashMap}. 81 * <p> 82 * The general contract of {@code hashCode} is: 83 * <ul> 84 * <li>Whenever it is invoked on the same object more than once during 85 * an execution of a Java application, the {@code hashCode} method 86 * must consistently return the same integer, provided no information 87 * used in {@code equals} comparisons on the object is modified. 88 * This integer need not remain consistent from one execution of an 89 * application to another execution of the same application. 90 * <li>If two objects are equal according to the {@code equals(Object)} 91 * method, then calling the {@code hashCode} method on each of 92 * the two objects must produce the same integer result. 93 * <li>It is <em>not</em> required that if two objects are unequal 94 * according to the {@link java.lang.Object#equals(java.lang.Object)} 95 * method, then calling the {@code hashCode} method on each of the 96 * two objects must produce distinct integer results. However, the 97 * programmer should be aware that producing distinct integer results 98 * for unequal objects may improve the performance of hash tables. 99 * </ul> 100 * <p> 101 * As much as is reasonably practical, the hashCode method defined by 102 * class {@code Object} does return distinct integers for distinct 103 * objects. (This is typically implemented by converting the internal 104 * address of the object into an integer, but this implementation 105 * technique is not required by the 106 * Java™ programming language.) 107 * 108 * @return a hash code value for this object. 109 * @see java.lang.Object#equals(java.lang.Object) 110 * @see java.lang.System#identityHashCode 111 */ 112 // BEGIN Android-changed: Added a local helper for identityHashCode. 113 // public native int hashCode(); hashCode()114 public int hashCode() { 115 return identityHashCode(this); 116 } 117 118 // Package-private to be used by j.l.System. We do the implementation here 119 // to avoid Object.hashCode doing a clinit check on j.l.System, and also 120 // to avoid leaking shadow$_monitor_ outside of this class. identityHashCode(Object obj)121 /* package-private */ static int identityHashCode(Object obj) { 122 int lockWord = obj.shadow$_monitor_; 123 final int lockWordStateMask = 0xC0000000; // Top 2 bits. 124 final int lockWordStateHash = 0x80000000; // Top 2 bits are value 2 (kStateHash). 125 final int lockWordHashMask = 0x0FFFFFFF; // Low 28 bits. 126 if ((lockWord & lockWordStateMask) == lockWordStateHash) { 127 return lockWord & lockWordHashMask; 128 } 129 return identityHashCodeNative(obj); 130 } 131 132 /** 133 * Return the identity hash code when the information in the monitor field 134 * is not sufficient. 135 */ 136 @FastNative identityHashCodeNative(Object obj)137 private static native int identityHashCodeNative(Object obj); 138 // END Android-changed: Added a local helper for identityHashCode. 139 140 /** 141 * Indicates whether some other object is "equal to" this one. 142 * <p> 143 * The {@code equals} method implements an equivalence relation 144 * on non-null object references: 145 * <ul> 146 * <li>It is <i>reflexive</i>: for any non-null reference value 147 * {@code x}, {@code x.equals(x)} should return 148 * {@code true}. 149 * <li>It is <i>symmetric</i>: for any non-null reference values 150 * {@code x} and {@code y}, {@code x.equals(y)} 151 * should return {@code true} if and only if 152 * {@code y.equals(x)} returns {@code true}. 153 * <li>It is <i>transitive</i>: for any non-null reference values 154 * {@code x}, {@code y}, and {@code z}, if 155 * {@code x.equals(y)} returns {@code true} and 156 * {@code y.equals(z)} returns {@code true}, then 157 * {@code x.equals(z)} should return {@code true}. 158 * <li>It is <i>consistent</i>: for any non-null reference values 159 * {@code x} and {@code y}, multiple invocations of 160 * {@code x.equals(y)} consistently return {@code true} 161 * or consistently return {@code false}, provided no 162 * information used in {@code equals} comparisons on the 163 * objects is modified. 164 * <li>For any non-null reference value {@code x}, 165 * {@code x.equals(null)} should return {@code false}. 166 * </ul> 167 * <p> 168 * The {@code equals} method for class {@code Object} implements 169 * the most discriminating possible equivalence relation on objects; 170 * that is, for any non-null reference values {@code x} and 171 * {@code y}, this method returns {@code true} if and only 172 * if {@code x} and {@code y} refer to the same object 173 * ({@code x == y} has the value {@code true}). 174 * <p> 175 * Note that it is generally necessary to override the {@code hashCode} 176 * method whenever this method is overridden, so as to maintain the 177 * general contract for the {@code hashCode} method, which states 178 * that equal objects must have equal hash codes. 179 * 180 * @param obj the reference object with which to compare. 181 * @return {@code true} if this object is the same as the obj 182 * argument; {@code false} otherwise. 183 * @see #hashCode() 184 * @see java.util.HashMap 185 */ equals(Object obj)186 public boolean equals(Object obj) { 187 return (this == obj); 188 } 189 190 /** 191 * Creates and returns a copy of this object. The precise meaning 192 * of "copy" may depend on the class of the object. The general 193 * intent is that, for any object {@code x}, the expression: 194 * <blockquote> 195 * <pre> 196 * x.clone() != x</pre></blockquote> 197 * will be true, and that the expression: 198 * <blockquote> 199 * <pre> 200 * x.clone().getClass() == x.getClass()</pre></blockquote> 201 * will be {@code true}, but these are not absolute requirements. 202 * While it is typically the case that: 203 * <blockquote> 204 * <pre> 205 * x.clone().equals(x)</pre></blockquote> 206 * will be {@code true}, this is not an absolute requirement. 207 * <p> 208 * By convention, the returned object should be obtained by calling 209 * {@code super.clone}. If a class and all of its superclasses (except 210 * {@code Object}) obey this convention, it will be the case that 211 * {@code x.clone().getClass() == x.getClass()}. 212 * <p> 213 * By convention, the object returned by this method should be independent 214 * of this object (which is being cloned). To achieve this independence, 215 * it may be necessary to modify one or more fields of the object returned 216 * by {@code super.clone} before returning it. Typically, this means 217 * copying any mutable objects that comprise the internal "deep structure" 218 * of the object being cloned and replacing the references to these 219 * objects with references to the copies. If a class contains only 220 * primitive fields or references to immutable objects, then it is usually 221 * the case that no fields in the object returned by {@code super.clone} 222 * need to be modified. 223 * <p> 224 * The method {@code clone} for class {@code Object} performs a 225 * specific cloning operation. First, if the class of this object does 226 * not implement the interface {@code Cloneable}, then a 227 * {@code CloneNotSupportedException} is thrown. Note that all arrays 228 * are considered to implement the interface {@code Cloneable} and that 229 * the return type of the {@code clone} method of an array type {@code T[]} 230 * is {@code T[]} where T is any reference or primitive type. 231 * Otherwise, this method creates a new instance of the class of this 232 * object and initializes all its fields with exactly the contents of 233 * the corresponding fields of this object, as if by assignment; the 234 * contents of the fields are not themselves cloned. Thus, this method 235 * performs a "shallow copy" of this object, not a "deep copy" operation. 236 * <p> 237 * The class {@code Object} does not itself implement the interface 238 * {@code Cloneable}, so calling the {@code clone} method on an object 239 * whose class is {@code Object} will result in throwing an 240 * exception at run time. 241 * 242 * @return a clone of this instance. 243 * @throws CloneNotSupportedException if the object's class does not 244 * support the {@code Cloneable} interface. Subclasses 245 * that override the {@code clone} method can also 246 * throw this exception to indicate that an instance cannot 247 * be cloned. 248 * @see java.lang.Cloneable 249 */ 250 // BEGIN Android-changed: Use native local helper for clone() 251 // Checks whether cloning is allowed before calling native local helper. 252 // protected native Object clone() throws CloneNotSupportedException; clone()253 protected Object clone() throws CloneNotSupportedException { 254 if (!(this instanceof Cloneable)) { 255 throw new CloneNotSupportedException("Class " + getClass().getName() + 256 " doesn't implement Cloneable"); 257 } 258 259 return internalClone(); 260 } 261 262 /* 263 * Native helper method for cloning. 264 */ 265 @FastNative internalClone()266 private native Object internalClone(); 267 // END Android-changed: Use native local helper for clone() 268 269 /** 270 * Returns a string representation of the object. In general, the 271 * {@code toString} method returns a string that 272 * "textually represents" this object. The result should 273 * be a concise but informative representation that is easy for a 274 * person to read. 275 * It is recommended that all subclasses override this method. 276 * <p> 277 * The {@code toString} method for class {@code Object} 278 * returns a string consisting of the name of the class of which the 279 * object is an instance, the at-sign character `{@code @}', and 280 * the unsigned hexadecimal representation of the hash code of the 281 * object. In other words, this method returns a string equal to the 282 * value of: 283 * <blockquote> 284 * <pre> 285 * getClass().getName() + '@' + Integer.toHexString(hashCode()) 286 * </pre></blockquote> 287 * 288 * @return a string representation of the object. 289 */ toString()290 public String toString() { 291 return getClass().getName() + "@" + Integer.toHexString(hashCode()); 292 } 293 294 /** 295 * Wakes up a single thread that is waiting on this object's 296 * monitor. If any threads are waiting on this object, one of them 297 * is chosen to be awakened. The choice is arbitrary and occurs at 298 * the discretion of the implementation. A thread waits on an object's 299 * monitor by calling one of the {@code wait} methods. 300 * <p> 301 * The awakened thread will not be able to proceed until the current 302 * thread relinquishes the lock on this object. The awakened thread will 303 * compete in the usual manner with any other threads that might be 304 * actively competing to synchronize on this object; for example, the 305 * awakened thread enjoys no reliable privilege or disadvantage in being 306 * the next thread to lock this object. 307 * <p> 308 * This method should only be called by a thread that is the owner 309 * of this object's monitor. A thread becomes the owner of the 310 * object's monitor in one of three ways: 311 * <ul> 312 * <li>By executing a synchronized instance method of that object. 313 * <li>By executing the body of a {@code synchronized} statement 314 * that synchronizes on the object. 315 * <li>For objects of type {@code Class,} by executing a 316 * synchronized static method of that class. 317 * </ul> 318 * <p> 319 * Only one thread at a time can own an object's monitor. 320 * 321 * @throws IllegalMonitorStateException if the current thread is not 322 * the owner of this object's monitor. 323 * @see java.lang.Object#notifyAll() 324 * @see java.lang.Object#wait() 325 */ 326 @FastNative notify()327 public final native void notify(); 328 329 /** 330 * Wakes up all threads that are waiting on this object's monitor. A 331 * thread waits on an object's monitor by calling one of the 332 * {@code wait} methods. 333 * <p> 334 * The awakened threads will not be able to proceed until the current 335 * thread relinquishes the lock on this object. The awakened threads 336 * will compete in the usual manner with any other threads that might 337 * be actively competing to synchronize on this object; for example, 338 * the awakened threads enjoy no reliable privilege or disadvantage in 339 * being the next thread to lock this object. 340 * <p> 341 * This method should only be called by a thread that is the owner 342 * of this object's monitor. See the {@code notify} method for a 343 * description of the ways in which a thread can become the owner of 344 * a monitor. 345 * 346 * @throws IllegalMonitorStateException if the current thread is not 347 * the owner of this object's monitor. 348 * @see java.lang.Object#notify() 349 * @see java.lang.Object#wait() 350 */ 351 @FastNative notifyAll()352 public final native void notifyAll(); 353 354 /** 355 * Causes the current thread to wait until either another thread invokes the 356 * {@link java.lang.Object#notify()} method or the 357 * {@link java.lang.Object#notifyAll()} method for this object, or a 358 * specified amount of time has elapsed. 359 * <p> 360 * The current thread must own this object's monitor. 361 * <p> 362 * This method causes the current thread (call it <var>T</var>) to 363 * place itself in the wait set for this object and then to relinquish 364 * any and all synchronization claims on this object. Thread <var>T</var> 365 * becomes disabled for thread scheduling purposes and lies dormant 366 * until one of four things happens: 367 * <ul> 368 * <li>Some other thread invokes the {@code notify} method for this 369 * object and thread <var>T</var> happens to be arbitrarily chosen as 370 * the thread to be awakened. 371 * <li>Some other thread invokes the {@code notifyAll} method for this 372 * object. 373 * <li>Some other thread {@linkplain Thread#interrupt() interrupts} 374 * thread <var>T</var>. 375 * <li>The specified amount of real time has elapsed, more or less. If 376 * {@code timeout} is zero, however, then real time is not taken into 377 * consideration and the thread simply waits until notified. 378 * </ul> 379 * The thread <var>T</var> is then removed from the wait set for this 380 * object and re-enabled for thread scheduling. It then competes in the 381 * usual manner with other threads for the right to synchronize on the 382 * object; once it has gained control of the object, all its 383 * synchronization claims on the object are restored to the status quo 384 * ante - that is, to the situation as of the time that the {@code wait} 385 * method was invoked. Thread <var>T</var> then returns from the 386 * invocation of the {@code wait} method. Thus, on return from the 387 * {@code wait} method, the synchronization state of the object and of 388 * thread {@code T} is exactly as it was when the {@code wait} method 389 * was invoked. 390 * <p> 391 * A thread can also wake up without being notified, interrupted, or 392 * timing out, a so-called <i>spurious wakeup</i>. While this will rarely 393 * occur in practice, applications must guard against it by testing for 394 * the condition that should have caused the thread to be awakened, and 395 * continuing to wait if the condition is not satisfied. In other words, 396 * waits should always occur in loops, like this one: 397 * <pre> 398 * synchronized (obj) { 399 * while (<condition does not hold>) 400 * obj.wait(timeout); 401 * ... // Perform action appropriate to condition 402 * } 403 * </pre> 404 * (For more information on this topic, see Section 3.2.3 in Doug Lea's 405 * "Concurrent Programming in Java (Second Edition)" (Addison-Wesley, 406 * 2000), or Item 50 in Joshua Bloch's "Effective Java Programming 407 * Language Guide" (Addison-Wesley, 2001). 408 * 409 * <p>If the current thread is {@linkplain java.lang.Thread#interrupt() 410 * interrupted} by any thread before or while it is waiting, then an 411 * {@code InterruptedException} is thrown. This exception is not 412 * thrown until the lock status of this object has been restored as 413 * described above. 414 * 415 * <p> 416 * Note that the {@code wait} method, as it places the current thread 417 * into the wait set for this object, unlocks only this object; any 418 * other objects on which the current thread may be synchronized remain 419 * locked while the thread waits. 420 * <p> 421 * This method should only be called by a thread that is the owner 422 * of this object's monitor. See the {@code notify} method for a 423 * description of the ways in which a thread can become the owner of 424 * a monitor. 425 * 426 * @param timeout the maximum time to wait in milliseconds. 427 * @throws IllegalArgumentException if the value of timeout is 428 * negative. 429 * @throws IllegalMonitorStateException if the current thread is not 430 * the owner of the object's monitor. 431 * @throws InterruptedException if any thread interrupted the 432 * current thread before or while the current thread 433 * was waiting for a notification. The <i>interrupted 434 * status</i> of the current thread is cleared when 435 * this exception is thrown. 436 * @see java.lang.Object#notify() 437 * @see java.lang.Object#notifyAll() 438 */ 439 // Android-changed: Implement wait(long) non-natively. 440 // public final native void wait(long timeout) throws InterruptedException; wait(long timeout)441 public final void wait(long timeout) throws InterruptedException { 442 wait(timeout, 0); 443 } 444 445 /** 446 * Causes the current thread to wait until another thread invokes the 447 * {@link java.lang.Object#notify()} method or the 448 * {@link java.lang.Object#notifyAll()} method for this object, or 449 * some other thread interrupts the current thread, or a certain 450 * amount of real time has elapsed. 451 * <p> 452 * This method is similar to the {@code wait} method of one 453 * argument, but it allows finer control over the amount of time to 454 * wait for a notification before giving up. The amount of real time, 455 * measured in nanoseconds, is given by: 456 * <blockquote> 457 * <pre> 458 * 1000000*timeout+nanos</pre></blockquote> 459 * <p> 460 * In all other respects, this method does the same thing as the 461 * method {@link #wait(long)} of one argument. In particular, 462 * {@code wait(0, 0)} means the same thing as {@code wait(0)}. 463 * <p> 464 * The current thread must own this object's monitor. The thread 465 * releases ownership of this monitor and waits until either of the 466 * following two conditions has occurred: 467 * <ul> 468 * <li>Another thread notifies threads waiting on this object's monitor 469 * to wake up either through a call to the {@code notify} method 470 * or the {@code notifyAll} method. 471 * <li>The timeout period, specified by {@code timeout} 472 * milliseconds plus {@code nanos} nanoseconds arguments, has 473 * elapsed. 474 * </ul> 475 * <p> 476 * The thread then waits until it can re-obtain ownership of the 477 * monitor and resumes execution. 478 * <p> 479 * As in the one argument version, interrupts and spurious wakeups are 480 * possible, and this method should always be used in a loop: 481 * <pre> 482 * synchronized (obj) { 483 * while (<condition does not hold>) 484 * obj.wait(timeout, nanos); 485 * ... // Perform action appropriate to condition 486 * } 487 * </pre> 488 * This method should only be called by a thread that is the owner 489 * of this object's monitor. See the {@code notify} method for a 490 * description of the ways in which a thread can become the owner of 491 * a monitor. 492 * 493 * @param timeout the maximum time to wait in milliseconds. 494 * @param nanos additional time, in nanoseconds range 495 * 0-999999. 496 * @throws IllegalArgumentException if the value of timeout is 497 * negative or the value of nanos is 498 * not in the range 0-999999. 499 * @throws IllegalMonitorStateException if the current thread is not 500 * the owner of this object's monitor. 501 * @throws InterruptedException if any thread interrupted the 502 * current thread before or while the current thread 503 * was waiting for a notification. The <i>interrupted 504 * status</i> of the current thread is cleared when 505 * this exception is thrown. 506 */ 507 // Android-changed: Implement wait(long, int) natively. 508 /* 509 public final void wait(long timeout, int nanos) throws InterruptedException { 510 if (timeout < 0) { 511 throw new IllegalArgumentException("timeout value is negative"); 512 } 513 514 if (nanos < 0 || nanos > 999999) { 515 throw new IllegalArgumentException( 516 "nanosecond timeout value out of range"); 517 } 518 519 if (nanos > 0) { 520 timeout++; 521 } 522 523 wait(timeout); 524 } 525 */ 526 @FastNative wait(long timeout, int nanos)527 public final native void wait(long timeout, int nanos) throws InterruptedException; 528 529 /** 530 * Causes the current thread to wait until another thread invokes the 531 * {@link java.lang.Object#notify()} method or the 532 * {@link java.lang.Object#notifyAll()} method for this object. 533 * In other words, this method behaves exactly as if it simply 534 * performs the call {@code wait(0)}. 535 * <p> 536 * The current thread must own this object's monitor. The thread 537 * releases ownership of this monitor and waits until another thread 538 * notifies threads waiting on this object's monitor to wake up 539 * either through a call to the {@code notify} method or the 540 * {@code notifyAll} method. The thread then waits until it can 541 * re-obtain ownership of the monitor and resumes execution. 542 * <p> 543 * As in the one argument version, interrupts and spurious wakeups are 544 * possible, and this method should always be used in a loop: 545 * <pre> 546 * synchronized (obj) { 547 * while (<condition does not hold>) 548 * obj.wait(); 549 * ... // Perform action appropriate to condition 550 * } 551 * </pre> 552 * This method should only be called by a thread that is the owner 553 * of this object's monitor. See the {@code notify} method for a 554 * description of the ways in which a thread can become the owner of 555 * a monitor. 556 * 557 * @throws IllegalMonitorStateException if the current thread is not 558 * the owner of the object's monitor. 559 * @throws InterruptedException if any thread interrupted the 560 * current thread before or while the current thread 561 * was waiting for a notification. The <i>interrupted 562 * status</i> of the current thread is cleared when 563 * this exception is thrown. 564 * @see java.lang.Object#notify() 565 * @see java.lang.Object#notifyAll() 566 */ wait()567 public final void wait() throws InterruptedException { 568 wait(0); 569 } 570 571 /** 572 * Called by the garbage collector on an object when garbage collection 573 * determines that there are no more references to the object. 574 * A subclass overrides the {@code finalize} method to dispose of 575 * system resources or to perform other cleanup. 576 * <p> 577 * The general contract of {@code finalize} is that it is invoked 578 * if and when the Java™ virtual 579 * machine has determined that there is no longer any 580 * means by which this object can be accessed by any thread that has 581 * not yet died, except as a result of an action taken by the 582 * finalization of some other object or class which is ready to be 583 * finalized. The {@code finalize} method may take any action, including 584 * making this object available again to other threads; the usual purpose 585 * of {@code finalize}, however, is to perform cleanup actions before 586 * the object is irrevocably discarded. For example, the finalize method 587 * for an object that represents an input/output connection might perform 588 * explicit I/O transactions to break the connection before the object is 589 * permanently discarded. 590 * <p> 591 * The {@code finalize} method of class {@code Object} performs no 592 * special action; it simply returns normally. Subclasses of 593 * {@code Object} may override this definition. 594 * <p> 595 * The Java programming language does not guarantee which thread will 596 * invoke the {@code finalize} method for any given object. It is 597 * guaranteed, however, that the thread that invokes finalize will not 598 * be holding any user-visible synchronization locks when finalize is 599 * invoked. If an uncaught exception is thrown by the finalize method, 600 * the exception is ignored and finalization of that object terminates. 601 * <p> 602 * After the {@code finalize} method has been invoked for an object, no 603 * further action is taken until the Java virtual machine has again 604 * determined that there is no longer any means by which this object can 605 * be accessed by any thread that has not yet died, including possible 606 * actions by other objects or classes which are ready to be finalized, 607 * at which point the object may be discarded. 608 * <p> 609 * The {@code finalize} method is never invoked more than once by a Java 610 * virtual machine for any given object. 611 * <p> 612 * Any exception thrown by the {@code finalize} method causes 613 * the finalization of this object to be halted, but is otherwise 614 * ignored. 615 * 616 * @throws Throwable the {@code Exception} raised by this method 617 * @see java.lang.ref.WeakReference 618 * @see java.lang.ref.PhantomReference 619 * @jls 12.6 Finalization of Class Instances 620 */ finalize()621 protected void finalize() throws Throwable { } 622 } 623