1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/emul/src/main/java/java/lang/Object.java Fri Sep 28 17:59:03 2012 +0200
1.3 @@ -0,0 +1,554 @@
1.4 +/*
1.5 + * Copyright (c) 1994, 2010, Oracle and/or its affiliates. All rights reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation. Oracle designates this
1.11 + * particular file as subject to the "Classpath" exception as provided
1.12 + * by Oracle in the LICENSE file that accompanied this code.
1.13 + *
1.14 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.15 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.16 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.17 + * version 2 for more details (a copy is included in the LICENSE file that
1.18 + * accompanied this code).
1.19 + *
1.20 + * You should have received a copy of the GNU General Public License version
1.21 + * 2 along with this work; if not, write to the Free Software Foundation,
1.22 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.23 + *
1.24 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.25 + * or visit www.oracle.com if you need additional information or have any
1.26 + * questions.
1.27 + */
1.28 +
1.29 +package java.lang;
1.30 +
1.31 +/**
1.32 + * Class {@code Object} is the root of the class hierarchy.
1.33 + * Every class has {@code Object} as a superclass. All objects,
1.34 + * including arrays, implement the methods of this class.
1.35 + *
1.36 + * @author unascribed
1.37 + * @see java.lang.Class
1.38 + * @since JDK1.0
1.39 + */
1.40 +public class Object {
1.41 +
1.42 + private static native void registerNatives();
1.43 + static {
1.44 + registerNatives();
1.45 + }
1.46 +
1.47 + /**
1.48 + * Returns the runtime class of this {@code Object}. The returned
1.49 + * {@code Class} object is the object that is locked by {@code
1.50 + * static synchronized} methods of the represented class.
1.51 + *
1.52 + * <p><b>The actual result type is {@code Class<? extends |X|>}
1.53 + * where {@code |X|} is the erasure of the static type of the
1.54 + * expression on which {@code getClass} is called.</b> For
1.55 + * example, no cast is required in this code fragment:</p>
1.56 + *
1.57 + * <p>
1.58 + * {@code Number n = 0; }<br>
1.59 + * {@code Class<? extends Number> c = n.getClass(); }
1.60 + * </p>
1.61 + *
1.62 + * @return The {@code Class} object that represents the runtime
1.63 + * class of this object.
1.64 + * @see Class Literals, section 15.8.2 of
1.65 + * <cite>The Java™ Language Specification</cite>.
1.66 + */
1.67 + public final native Class<?> getClass();
1.68 +
1.69 + /**
1.70 + * Returns a hash code value for the object. This method is
1.71 + * supported for the benefit of hash tables such as those provided by
1.72 + * {@link java.util.HashMap}.
1.73 + * <p>
1.74 + * The general contract of {@code hashCode} is:
1.75 + * <ul>
1.76 + * <li>Whenever it is invoked on the same object more than once during
1.77 + * an execution of a Java application, the {@code hashCode} method
1.78 + * must consistently return the same integer, provided no information
1.79 + * used in {@code equals} comparisons on the object is modified.
1.80 + * This integer need not remain consistent from one execution of an
1.81 + * application to another execution of the same application.
1.82 + * <li>If two objects are equal according to the {@code equals(Object)}
1.83 + * method, then calling the {@code hashCode} method on each of
1.84 + * the two objects must produce the same integer result.
1.85 + * <li>It is <em>not</em> required that if two objects are unequal
1.86 + * according to the {@link java.lang.Object#equals(java.lang.Object)}
1.87 + * method, then calling the {@code hashCode} method on each of the
1.88 + * two objects must produce distinct integer results. However, the
1.89 + * programmer should be aware that producing distinct integer results
1.90 + * for unequal objects may improve the performance of hash tables.
1.91 + * </ul>
1.92 + * <p>
1.93 + * As much as is reasonably practical, the hashCode method defined by
1.94 + * class {@code Object} does return distinct integers for distinct
1.95 + * objects. (This is typically implemented by converting the internal
1.96 + * address of the object into an integer, but this implementation
1.97 + * technique is not required by the
1.98 + * Java<font size="-2"><sup>TM</sup></font> programming language.)
1.99 + *
1.100 + * @return a hash code value for this object.
1.101 + * @see java.lang.Object#equals(java.lang.Object)
1.102 + * @see java.lang.System#identityHashCode
1.103 + */
1.104 + public native int hashCode();
1.105 +
1.106 + /**
1.107 + * Indicates whether some other object is "equal to" this one.
1.108 + * <p>
1.109 + * The {@code equals} method implements an equivalence relation
1.110 + * on non-null object references:
1.111 + * <ul>
1.112 + * <li>It is <i>reflexive</i>: for any non-null reference value
1.113 + * {@code x}, {@code x.equals(x)} should return
1.114 + * {@code true}.
1.115 + * <li>It is <i>symmetric</i>: for any non-null reference values
1.116 + * {@code x} and {@code y}, {@code x.equals(y)}
1.117 + * should return {@code true} if and only if
1.118 + * {@code y.equals(x)} returns {@code true}.
1.119 + * <li>It is <i>transitive</i>: for any non-null reference values
1.120 + * {@code x}, {@code y}, and {@code z}, if
1.121 + * {@code x.equals(y)} returns {@code true} and
1.122 + * {@code y.equals(z)} returns {@code true}, then
1.123 + * {@code x.equals(z)} should return {@code true}.
1.124 + * <li>It is <i>consistent</i>: for any non-null reference values
1.125 + * {@code x} and {@code y}, multiple invocations of
1.126 + * {@code x.equals(y)} consistently return {@code true}
1.127 + * or consistently return {@code false}, provided no
1.128 + * information used in {@code equals} comparisons on the
1.129 + * objects is modified.
1.130 + * <li>For any non-null reference value {@code x},
1.131 + * {@code x.equals(null)} should return {@code false}.
1.132 + * </ul>
1.133 + * <p>
1.134 + * The {@code equals} method for class {@code Object} implements
1.135 + * the most discriminating possible equivalence relation on objects;
1.136 + * that is, for any non-null reference values {@code x} and
1.137 + * {@code y}, this method returns {@code true} if and only
1.138 + * if {@code x} and {@code y} refer to the same object
1.139 + * ({@code x == y} has the value {@code true}).
1.140 + * <p>
1.141 + * Note that it is generally necessary to override the {@code hashCode}
1.142 + * method whenever this method is overridden, so as to maintain the
1.143 + * general contract for the {@code hashCode} method, which states
1.144 + * that equal objects must have equal hash codes.
1.145 + *
1.146 + * @param obj the reference object with which to compare.
1.147 + * @return {@code true} if this object is the same as the obj
1.148 + * argument; {@code false} otherwise.
1.149 + * @see #hashCode()
1.150 + * @see java.util.HashMap
1.151 + */
1.152 + public boolean equals(Object obj) {
1.153 + return (this == obj);
1.154 + }
1.155 +
1.156 + /**
1.157 + * Creates and returns a copy of this object. The precise meaning
1.158 + * of "copy" may depend on the class of the object. The general
1.159 + * intent is that, for any object {@code x}, the expression:
1.160 + * <blockquote>
1.161 + * <pre>
1.162 + * x.clone() != x</pre></blockquote>
1.163 + * will be true, and that the expression:
1.164 + * <blockquote>
1.165 + * <pre>
1.166 + * x.clone().getClass() == x.getClass()</pre></blockquote>
1.167 + * will be {@code true}, but these are not absolute requirements.
1.168 + * While it is typically the case that:
1.169 + * <blockquote>
1.170 + * <pre>
1.171 + * x.clone().equals(x)</pre></blockquote>
1.172 + * will be {@code true}, this is not an absolute requirement.
1.173 + * <p>
1.174 + * By convention, the returned object should be obtained by calling
1.175 + * {@code super.clone}. If a class and all of its superclasses (except
1.176 + * {@code Object}) obey this convention, it will be the case that
1.177 + * {@code x.clone().getClass() == x.getClass()}.
1.178 + * <p>
1.179 + * By convention, the object returned by this method should be independent
1.180 + * of this object (which is being cloned). To achieve this independence,
1.181 + * it may be necessary to modify one or more fields of the object returned
1.182 + * by {@code super.clone} before returning it. Typically, this means
1.183 + * copying any mutable objects that comprise the internal "deep structure"
1.184 + * of the object being cloned and replacing the references to these
1.185 + * objects with references to the copies. If a class contains only
1.186 + * primitive fields or references to immutable objects, then it is usually
1.187 + * the case that no fields in the object returned by {@code super.clone}
1.188 + * need to be modified.
1.189 + * <p>
1.190 + * The method {@code clone} for class {@code Object} performs a
1.191 + * specific cloning operation. First, if the class of this object does
1.192 + * not implement the interface {@code Cloneable}, then a
1.193 + * {@code CloneNotSupportedException} is thrown. Note that all arrays
1.194 + * are considered to implement the interface {@code Cloneable} and that
1.195 + * the return type of the {@code clone} method of an array type {@code T[]}
1.196 + * is {@code T[]} where T is any reference or primitive type.
1.197 + * Otherwise, this method creates a new instance of the class of this
1.198 + * object and initializes all its fields with exactly the contents of
1.199 + * the corresponding fields of this object, as if by assignment; the
1.200 + * contents of the fields are not themselves cloned. Thus, this method
1.201 + * performs a "shallow copy" of this object, not a "deep copy" operation.
1.202 + * <p>
1.203 + * The class {@code Object} does not itself implement the interface
1.204 + * {@code Cloneable}, so calling the {@code clone} method on an object
1.205 + * whose class is {@code Object} will result in throwing an
1.206 + * exception at run time.
1.207 + *
1.208 + * @return a clone of this instance.
1.209 + * @exception CloneNotSupportedException if the object's class does not
1.210 + * support the {@code Cloneable} interface. Subclasses
1.211 + * that override the {@code clone} method can also
1.212 + * throw this exception to indicate that an instance cannot
1.213 + * be cloned.
1.214 + * @see java.lang.Cloneable
1.215 + */
1.216 + protected native Object clone() throws CloneNotSupportedException;
1.217 +
1.218 + /**
1.219 + * Returns a string representation of the object. In general, the
1.220 + * {@code toString} method returns a string that
1.221 + * "textually represents" this object. The result should
1.222 + * be a concise but informative representation that is easy for a
1.223 + * person to read.
1.224 + * It is recommended that all subclasses override this method.
1.225 + * <p>
1.226 + * The {@code toString} method for class {@code Object}
1.227 + * returns a string consisting of the name of the class of which the
1.228 + * object is an instance, the at-sign character `{@code @}', and
1.229 + * the unsigned hexadecimal representation of the hash code of the
1.230 + * object. In other words, this method returns a string equal to the
1.231 + * value of:
1.232 + * <blockquote>
1.233 + * <pre>
1.234 + * getClass().getName() + '@' + Integer.toHexString(hashCode())
1.235 + * </pre></blockquote>
1.236 + *
1.237 + * @return a string representation of the object.
1.238 + */
1.239 + public String toString() {
1.240 + return getClass().getName() + "@" + Integer.toHexString(hashCode());
1.241 + }
1.242 +
1.243 + /**
1.244 + * Wakes up a single thread that is waiting on this object's
1.245 + * monitor. If any threads are waiting on this object, one of them
1.246 + * is chosen to be awakened. The choice is arbitrary and occurs at
1.247 + * the discretion of the implementation. A thread waits on an object's
1.248 + * monitor by calling one of the {@code wait} methods.
1.249 + * <p>
1.250 + * The awakened thread will not be able to proceed until the current
1.251 + * thread relinquishes the lock on this object. The awakened thread will
1.252 + * compete in the usual manner with any other threads that might be
1.253 + * actively competing to synchronize on this object; for example, the
1.254 + * awakened thread enjoys no reliable privilege or disadvantage in being
1.255 + * the next thread to lock this object.
1.256 + * <p>
1.257 + * This method should only be called by a thread that is the owner
1.258 + * of this object's monitor. A thread becomes the owner of the
1.259 + * object's monitor in one of three ways:
1.260 + * <ul>
1.261 + * <li>By executing a synchronized instance method of that object.
1.262 + * <li>By executing the body of a {@code synchronized} statement
1.263 + * that synchronizes on the object.
1.264 + * <li>For objects of type {@code Class,} by executing a
1.265 + * synchronized static method of that class.
1.266 + * </ul>
1.267 + * <p>
1.268 + * Only one thread at a time can own an object's monitor.
1.269 + *
1.270 + * @exception IllegalMonitorStateException if the current thread is not
1.271 + * the owner of this object's monitor.
1.272 + * @see java.lang.Object#notifyAll()
1.273 + * @see java.lang.Object#wait()
1.274 + */
1.275 + public final native void notify();
1.276 +
1.277 + /**
1.278 + * Wakes up all threads that are waiting on this object's monitor. A
1.279 + * thread waits on an object's monitor by calling one of the
1.280 + * {@code wait} methods.
1.281 + * <p>
1.282 + * The awakened threads will not be able to proceed until the current
1.283 + * thread relinquishes the lock on this object. The awakened threads
1.284 + * will compete in the usual manner with any other threads that might
1.285 + * be actively competing to synchronize on this object; for example,
1.286 + * the awakened threads enjoy no reliable privilege or disadvantage in
1.287 + * being the next thread to lock this object.
1.288 + * <p>
1.289 + * This method should only be called by a thread that is the owner
1.290 + * of this object's monitor. See the {@code notify} method for a
1.291 + * description of the ways in which a thread can become the owner of
1.292 + * a monitor.
1.293 + *
1.294 + * @exception IllegalMonitorStateException if the current thread is not
1.295 + * the owner of this object's monitor.
1.296 + * @see java.lang.Object#notify()
1.297 + * @see java.lang.Object#wait()
1.298 + */
1.299 + public final native void notifyAll();
1.300 +
1.301 + /**
1.302 + * Causes the current thread to wait until either another thread invokes the
1.303 + * {@link java.lang.Object#notify()} method or the
1.304 + * {@link java.lang.Object#notifyAll()} method for this object, or a
1.305 + * specified amount of time has elapsed.
1.306 + * <p>
1.307 + * The current thread must own this object's monitor.
1.308 + * <p>
1.309 + * This method causes the current thread (call it <var>T</var>) to
1.310 + * place itself in the wait set for this object and then to relinquish
1.311 + * any and all synchronization claims on this object. Thread <var>T</var>
1.312 + * becomes disabled for thread scheduling purposes and lies dormant
1.313 + * until one of four things happens:
1.314 + * <ul>
1.315 + * <li>Some other thread invokes the {@code notify} method for this
1.316 + * object and thread <var>T</var> happens to be arbitrarily chosen as
1.317 + * the thread to be awakened.
1.318 + * <li>Some other thread invokes the {@code notifyAll} method for this
1.319 + * object.
1.320 + * <li>Some other thread {@linkplain Thread#interrupt() interrupts}
1.321 + * thread <var>T</var>.
1.322 + * <li>The specified amount of real time has elapsed, more or less. If
1.323 + * {@code timeout} is zero, however, then real time is not taken into
1.324 + * consideration and the thread simply waits until notified.
1.325 + * </ul>
1.326 + * The thread <var>T</var> is then removed from the wait set for this
1.327 + * object and re-enabled for thread scheduling. It then competes in the
1.328 + * usual manner with other threads for the right to synchronize on the
1.329 + * object; once it has gained control of the object, all its
1.330 + * synchronization claims on the object are restored to the status quo
1.331 + * ante - that is, to the situation as of the time that the {@code wait}
1.332 + * method was invoked. Thread <var>T</var> then returns from the
1.333 + * invocation of the {@code wait} method. Thus, on return from the
1.334 + * {@code wait} method, the synchronization state of the object and of
1.335 + * thread {@code T} is exactly as it was when the {@code wait} method
1.336 + * was invoked.
1.337 + * <p>
1.338 + * A thread can also wake up without being notified, interrupted, or
1.339 + * timing out, a so-called <i>spurious wakeup</i>. While this will rarely
1.340 + * occur in practice, applications must guard against it by testing for
1.341 + * the condition that should have caused the thread to be awakened, and
1.342 + * continuing to wait if the condition is not satisfied. In other words,
1.343 + * waits should always occur in loops, like this one:
1.344 + * <pre>
1.345 + * synchronized (obj) {
1.346 + * while (<condition does not hold>)
1.347 + * obj.wait(timeout);
1.348 + * ... // Perform action appropriate to condition
1.349 + * }
1.350 + * </pre>
1.351 + * (For more information on this topic, see Section 3.2.3 in Doug Lea's
1.352 + * "Concurrent Programming in Java (Second Edition)" (Addison-Wesley,
1.353 + * 2000), or Item 50 in Joshua Bloch's "Effective Java Programming
1.354 + * Language Guide" (Addison-Wesley, 2001).
1.355 + *
1.356 + * <p>If the current thread is {@linkplain java.lang.Thread#interrupt()
1.357 + * interrupted} by any thread before or while it is waiting, then an
1.358 + * {@code InterruptedException} is thrown. This exception is not
1.359 + * thrown until the lock status of this object has been restored as
1.360 + * described above.
1.361 + *
1.362 + * <p>
1.363 + * Note that the {@code wait} method, as it places the current thread
1.364 + * into the wait set for this object, unlocks only this object; any
1.365 + * other objects on which the current thread may be synchronized remain
1.366 + * locked while the thread waits.
1.367 + * <p>
1.368 + * This method should only be called by a thread that is the owner
1.369 + * of this object's monitor. See the {@code notify} method for a
1.370 + * description of the ways in which a thread can become the owner of
1.371 + * a monitor.
1.372 + *
1.373 + * @param timeout the maximum time to wait in milliseconds.
1.374 + * @exception IllegalArgumentException if the value of timeout is
1.375 + * negative.
1.376 + * @exception IllegalMonitorStateException if the current thread is not
1.377 + * the owner of the object's monitor.
1.378 + * @exception InterruptedException if any thread interrupted the
1.379 + * current thread before or while the current thread
1.380 + * was waiting for a notification. The <i>interrupted
1.381 + * status</i> of the current thread is cleared when
1.382 + * this exception is thrown.
1.383 + * @see java.lang.Object#notify()
1.384 + * @see java.lang.Object#notifyAll()
1.385 + */
1.386 + public final native void wait(long timeout) throws InterruptedException;
1.387 +
1.388 + /**
1.389 + * Causes the current thread to wait until another thread invokes the
1.390 + * {@link java.lang.Object#notify()} method or the
1.391 + * {@link java.lang.Object#notifyAll()} method for this object, or
1.392 + * some other thread interrupts the current thread, or a certain
1.393 + * amount of real time has elapsed.
1.394 + * <p>
1.395 + * This method is similar to the {@code wait} method of one
1.396 + * argument, but it allows finer control over the amount of time to
1.397 + * wait for a notification before giving up. The amount of real time,
1.398 + * measured in nanoseconds, is given by:
1.399 + * <blockquote>
1.400 + * <pre>
1.401 + * 1000000*timeout+nanos</pre></blockquote>
1.402 + * <p>
1.403 + * In all other respects, this method does the same thing as the
1.404 + * method {@link #wait(long)} of one argument. In particular,
1.405 + * {@code wait(0, 0)} means the same thing as {@code wait(0)}.
1.406 + * <p>
1.407 + * The current thread must own this object's monitor. The thread
1.408 + * releases ownership of this monitor and waits until either of the
1.409 + * following two conditions has occurred:
1.410 + * <ul>
1.411 + * <li>Another thread notifies threads waiting on this object's monitor
1.412 + * to wake up either through a call to the {@code notify} method
1.413 + * or the {@code notifyAll} method.
1.414 + * <li>The timeout period, specified by {@code timeout}
1.415 + * milliseconds plus {@code nanos} nanoseconds arguments, has
1.416 + * elapsed.
1.417 + * </ul>
1.418 + * <p>
1.419 + * The thread then waits until it can re-obtain ownership of the
1.420 + * monitor and resumes execution.
1.421 + * <p>
1.422 + * As in the one argument version, interrupts and spurious wakeups are
1.423 + * possible, and this method should always be used in a loop:
1.424 + * <pre>
1.425 + * synchronized (obj) {
1.426 + * while (<condition does not hold>)
1.427 + * obj.wait(timeout, nanos);
1.428 + * ... // Perform action appropriate to condition
1.429 + * }
1.430 + * </pre>
1.431 + * This method should only be called by a thread that is the owner
1.432 + * of this object's monitor. See the {@code notify} method for a
1.433 + * description of the ways in which a thread can become the owner of
1.434 + * a monitor.
1.435 + *
1.436 + * @param timeout the maximum time to wait in milliseconds.
1.437 + * @param nanos additional time, in nanoseconds range
1.438 + * 0-999999.
1.439 + * @exception IllegalArgumentException if the value of timeout is
1.440 + * negative or the value of nanos is
1.441 + * not in the range 0-999999.
1.442 + * @exception IllegalMonitorStateException if the current thread is not
1.443 + * the owner of this object's monitor.
1.444 + * @exception InterruptedException if any thread interrupted the
1.445 + * current thread before or while the current thread
1.446 + * was waiting for a notification. The <i>interrupted
1.447 + * status</i> of the current thread is cleared when
1.448 + * this exception is thrown.
1.449 + */
1.450 + public final void wait(long timeout, int nanos) throws InterruptedException {
1.451 + if (timeout < 0) {
1.452 + throw new IllegalArgumentException("timeout value is negative");
1.453 + }
1.454 +
1.455 + if (nanos < 0 || nanos > 999999) {
1.456 + throw new IllegalArgumentException(
1.457 + "nanosecond timeout value out of range");
1.458 + }
1.459 +
1.460 + if (nanos >= 500000 || (nanos != 0 && timeout == 0)) {
1.461 + timeout++;
1.462 + }
1.463 +
1.464 + wait(timeout);
1.465 + }
1.466 +
1.467 + /**
1.468 + * Causes the current thread to wait until another thread invokes the
1.469 + * {@link java.lang.Object#notify()} method or the
1.470 + * {@link java.lang.Object#notifyAll()} method for this object.
1.471 + * In other words, this method behaves exactly as if it simply
1.472 + * performs the call {@code wait(0)}.
1.473 + * <p>
1.474 + * The current thread must own this object's monitor. The thread
1.475 + * releases ownership of this monitor and waits until another thread
1.476 + * notifies threads waiting on this object's monitor to wake up
1.477 + * either through a call to the {@code notify} method or the
1.478 + * {@code notifyAll} method. The thread then waits until it can
1.479 + * re-obtain ownership of the monitor and resumes execution.
1.480 + * <p>
1.481 + * As in the one argument version, interrupts and spurious wakeups are
1.482 + * possible, and this method should always be used in a loop:
1.483 + * <pre>
1.484 + * synchronized (obj) {
1.485 + * while (<condition does not hold>)
1.486 + * obj.wait();
1.487 + * ... // Perform action appropriate to condition
1.488 + * }
1.489 + * </pre>
1.490 + * This method should only be called by a thread that is the owner
1.491 + * of this object's monitor. See the {@code notify} method for a
1.492 + * description of the ways in which a thread can become the owner of
1.493 + * a monitor.
1.494 + *
1.495 + * @exception IllegalMonitorStateException if the current thread is not
1.496 + * the owner of the object's monitor.
1.497 + * @exception InterruptedException if any thread interrupted the
1.498 + * current thread before or while the current thread
1.499 + * was waiting for a notification. The <i>interrupted
1.500 + * status</i> of the current thread is cleared when
1.501 + * this exception is thrown.
1.502 + * @see java.lang.Object#notify()
1.503 + * @see java.lang.Object#notifyAll()
1.504 + */
1.505 + public final void wait() throws InterruptedException {
1.506 + wait(0);
1.507 + }
1.508 +
1.509 + /**
1.510 + * Called by the garbage collector on an object when garbage collection
1.511 + * determines that there are no more references to the object.
1.512 + * A subclass overrides the {@code finalize} method to dispose of
1.513 + * system resources or to perform other cleanup.
1.514 + * <p>
1.515 + * The general contract of {@code finalize} is that it is invoked
1.516 + * if and when the Java<font size="-2"><sup>TM</sup></font> virtual
1.517 + * machine has determined that there is no longer any
1.518 + * means by which this object can be accessed by any thread that has
1.519 + * not yet died, except as a result of an action taken by the
1.520 + * finalization of some other object or class which is ready to be
1.521 + * finalized. The {@code finalize} method may take any action, including
1.522 + * making this object available again to other threads; the usual purpose
1.523 + * of {@code finalize}, however, is to perform cleanup actions before
1.524 + * the object is irrevocably discarded. For example, the finalize method
1.525 + * for an object that represents an input/output connection might perform
1.526 + * explicit I/O transactions to break the connection before the object is
1.527 + * permanently discarded.
1.528 + * <p>
1.529 + * The {@code finalize} method of class {@code Object} performs no
1.530 + * special action; it simply returns normally. Subclasses of
1.531 + * {@code Object} may override this definition.
1.532 + * <p>
1.533 + * The Java programming language does not guarantee which thread will
1.534 + * invoke the {@code finalize} method for any given object. It is
1.535 + * guaranteed, however, that the thread that invokes finalize will not
1.536 + * be holding any user-visible synchronization locks when finalize is
1.537 + * invoked. If an uncaught exception is thrown by the finalize method,
1.538 + * the exception is ignored and finalization of that object terminates.
1.539 + * <p>
1.540 + * After the {@code finalize} method has been invoked for an object, no
1.541 + * further action is taken until the Java virtual machine has again
1.542 + * determined that there is no longer any means by which this object can
1.543 + * be accessed by any thread that has not yet died, including possible
1.544 + * actions by other objects or classes which are ready to be finalized,
1.545 + * at which point the object may be discarded.
1.546 + * <p>
1.547 + * The {@code finalize} method is never invoked more than once by a Java
1.548 + * virtual machine for any given object.
1.549 + * <p>
1.550 + * Any exception thrown by the {@code finalize} method causes
1.551 + * the finalization of this object to be halted, but is otherwise
1.552 + * ignored.
1.553 + *
1.554 + * @throws Throwable the {@code Exception} raised by this method
1.555 + */
1.556 + protected void finalize() throws Throwable { }
1.557 +}