1 /*
2 * Copyright (c) 2004, 2018, 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.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24 package java.lang;
25
26 import nsk.jvmti.scenarios.bcinstr.BI04.bi04t002a;
27
28 /**
29 * Class <code>Object</code> is the root of the class hierarchy.
30 * Every class has <code>Object</code> as a superclass. All objects,
31 * including arrays, implement the methods of this class.
32 *
33 * @author unascribed
34 * @version 1.67, 02/03/04
35 * @see java.lang.Class
36 * @since JDK1.0
37 */
38 public class Object {
39
40 private static native void registerNatives();
41 static {
42 registerNatives();
43 }
44
45 /**
46 * Returns the runtime class of an object. That <tt>Class</tt>
47 * object is the object that is locked by <tt>static synchronized</tt>
48 * methods of the represented class.
49 *
50 * @return The <code>java.lang.Class</code> object that represents
51 * the runtime class of the object. The result is of type
52 * {@code Class<? extends X>} where X is the
53 * static type of the expression on which
54 * <code>getClass</code> is called.
55 */
56 public final native Class<? extends Object> getClass();
57
58 /**
59 * Returns a hash code value for the object. This method is
60 * supported for the benefit of hashtables such as those provided by
61 * <code>java.util.Hashtable</code>.
62 * <p>
63 * The general contract of <code>hashCode</code> is:
64 * <ul>
65 * <li>Whenever it is invoked on the same object more than once during
66 * an execution of a Java application, the <tt>hashCode</tt> method
67 * must consistently return the same integer, provided no information
68 * used in <tt>equals</tt> comparisons on the object is modified.
69 * This integer need not remain consistent from one execution of an
70 * application to another execution of the same application.
71 * <li>If two objects are equal according to the <tt>equals(Object)</tt>
72 * method, then calling the <code>hashCode</code> method on each of
73 * the two objects must produce the same integer result.
74 * <li>It is <em>not</em> required that if two objects are unequal
75 * according to the {@link java.lang.Object#equals(java.lang.Object)}
76 * method, then calling the <tt>hashCode</tt> method on each of the
77 * two objects must produce distinct integer results. However, the
78 * programmer should be aware that producing distinct integer results
79 * for unequal objects may improve the performance of hashtables.
80 * </ul>
81 * <p>
82 * As much as is reasonably practical, the hashCode method defined by
83 * class <tt>Object</tt> does return distinct integers for distinct
84 * objects. (This is typically implemented by converting the internal
85 * address of the object into an integer, but this implementation
86 * technique is not required by the
87 * Java<font size="-2"><sup>TM</sup></font> programming language.)
88 *
89 * @return a hash code value for this object.
90 * @see java.lang.Object#equals(java.lang.Object)
91 * @see java.util.Hashtable
92 */
93 public native int hashCode();
94
95 /**
96 * Indicates whether some other object is "equal to" this one.
97 * <p>
98 * The <code>equals</code> method implements an equivalence relation
99 * on non-null object references:
100 * <ul>
101 * <li>It is <i>reflexive</i>: for any non-null reference value
102 * <code>x</code>, <code>x.equals(x)</code> should return
103 * <code>true</code>.
104 * <li>It is <i>symmetric</i>: for any non-null reference values
105 * <code>x</code> and <code>y</code>, <code>x.equals(y)</code>
106 * should return <code>true</code> if and only if
107 * <code>y.equals(x)</code> returns <code>true</code>.
108 * <li>It is <i>transitive</i>: for any non-null reference values
109 * <code>x</code>, <code>y</code>, and <code>z</code>, if
110 * <code>x.equals(y)</code> returns <code>true</code> and
111 * <code>y.equals(z)</code> returns <code>true</code>, then
112 * <code>x.equals(z)</code> should return <code>true</code>.
113 * <li>It is <i>consistent</i>: for any non-null reference values
114 * <code>x</code> and <code>y</code>, multiple invocations of
115 * <tt>x.equals(y)</tt> consistently return <code>true</code>
116 * or consistently return <code>false</code>, provided no
117 * information used in <code>equals</code> comparisons on the
118 * objects is modified.
119 * <li>For any non-null reference value <code>x</code>,
120 * <code>x.equals(null)</code> should return <code>false</code>.
121 * </ul>
122 * <p>
123 * The <tt>equals</tt> method for class <code>Object</code> implements
124 * the most discriminating possible equivalence relation on objects;
125 * that is, for any non-null reference values <code>x</code> and
126 * <code>y</code>, this method returns <code>true</code> if and only
127 * if <code>x</code> and <code>y</code> refer to the same object
128 * (<code>x == y</code> has the value <code>true</code>).
129 * <p>
130 * Note that it is generally necessary to override the <tt>hashCode</tt>
131 * method whenever this method is overridden, so as to maintain the
132 * general contract for the <tt>hashCode</tt> method, which states
133 * that equal objects must have equal hash codes.
134 *
135 * @param obj the reference object with which to compare.
136 * @return <code>true</code> if this object is the same as the obj
137 * argument; <code>false</code> otherwise.
138 * @see #hashCode()
139 * @see java.util.Hashtable
140 */
141 public boolean equals(Object obj) {
142 bi04t002a.instrInvoke(bi04t002a.INSTR_EQUALS);
143 return (this == obj);
144 }
145
146 /**
147 * Creates and returns a copy of this object. The precise meaning
148 * of "copy" may depend on the class of the object. The general
149 * intent is that, for any object <tt>x</tt>, the expression:
150 * <blockquote>
151 * <pre>
152 * x.clone() != x</pre></blockquote>
153 * will be true, and that the expression:
154 * <blockquote>
155 * <pre>
156 * x.clone().getClass() == x.getClass()</pre></blockquote>
157 * will be <tt>true</tt>, but these are not absolute requirements.
158 * While it is typically the case that:
159 * <blockquote>
160 * <pre>
161 * x.clone().equals(x)</pre></blockquote>
162 * will be <tt>true</tt>, this is not an absolute requirement.
163 * <p>
164 * By convention, the returned object should be obtained by calling
165 * <tt>super.clone</tt>. If a class and all of its superclasses (except
166 * <tt>Object</tt>) obey this convention, it will be the case that
167 * <tt>x.clone().getClass() == x.getClass()</tt>.
168 * <p>
169 * By convention, the object returned by this method should be independent
170 * of this object (which is being cloned). To achieve this independence,
171 * it may be necessary to modify one or more fields of the object returned
172 * by <tt>super.clone</tt> before returning it. Typically, this means
173 * copying any mutable objects that comprise the internal "deep structure"
174 * of the object being cloned and replacing the references to these
175 * objects with references to the copies. If a class contains only
176 * primitive fields or references to immutable objects, then it is usually
177 * the case that no fields in the object returned by <tt>super.clone</tt>
178 * need to be modified.
179 * <p>
180 * The method <tt>clone</tt> for class <tt>Object</tt> performs a
181 * specific cloning operation. First, if the class of this object does
182 * not implement the interface <tt>Cloneable</tt>, then a
183 * <tt>CloneNotSupportedException</tt> is thrown. Note that all arrays
184 * are considered to implement the interface <tt>Cloneable</tt>.
185 * Otherwise, this method creates a new instance of the class of this
186 * object and initializes all its fields with exactly the contents of
187 * the corresponding fields of this object, as if by assignment; the
188 * contents of the fields are not themselves cloned. Thus, this method
189 * performs a "shallow copy" of this object, not a "deep copy" operation.
190 * <p>
191 * The class <tt>Object</tt> does not itself implement the interface
192 * <tt>Cloneable</tt>, so calling the <tt>clone</tt> method on an object
193 * whose class is <tt>Object</tt> will result in throwing an
194 * exception at run time.
195 *
196 * @return a clone of this instance.
197 * @exception CloneNotSupportedException if the object's class does not
198 * support the <code>Cloneable</code> interface. Subclasses
199 * that override the <code>clone</code> method can also
200 * throw this exception to indicate that an instance cannot
201 * be cloned.
202 * @see java.lang.Cloneable
203 */
204 protected native Object clone() throws CloneNotSupportedException;
205
206 /**
207 * Returns a string representation of the object. In general, the
208 * <code>toString</code> method returns a string that
209 * "textually represents" this object. The result should
210 * be a concise but informative representation that is easy for a
211 * person to read.
212 * It is recommended that all subclasses override this method.
213 * <p>
214 * The <code>toString</code> method for class <code>Object</code>
215 * returns a string consisting of the name of the class of which the
216 * object is an instance, the at-sign character `<code>@</code>', and
217 * the unsigned hexadecimal representation of the hash code of the
218 * object. In other words, this method returns a string equal to the
219 * value of:
220 * <blockquote>
221 * <pre>
222 * getClass().getName() + '@' + Integer.toHexString(hashCode())
223 * </pre></blockquote>
224 *
225 * @return a string representation of the object.
226 */
227 public String toString() {
228 bi04t002a.instrInvoke(bi04t002a.INSTR_TOSTRING);
229 return getClass().getName() + "@" + Integer.toHexString(hashCode());
230 }
231
232 /**
233 * Wakes up a single thread that is waiting on this object's
234 * monitor. If any threads are waiting on this object, one of them
235 * is chosen to be awakened. The choice is arbitrary and occurs at
236 * the discretion of the implementation. A thread waits on an object's
237 * monitor by calling one of the <code>wait</code> methods.
238 * <p>
239 * The awakened thread will not be able to proceed until the current
240 * thread relinquishes the lock on this object. The awakened thread will
241 * compete in the usual manner with any other threads that might be
242 * actively competing to synchronize on this object; for example, the
243 * awakened thread enjoys no reliable privilege or disadvantage in being
244 * the next thread to lock this object.
245 * <p>
246 * This method should only be called by a thread that is the owner
247 * of this object's monitor. A thread becomes the owner of the
248 * object's monitor in one of three ways:
249 * <ul>
250 * <li>By executing a synchronized instance method of that object.
251 * <li>By executing the body of a <code>synchronized</code> statement
252 * that synchronizes on the object.
253 * <li>For objects of type <code>Class,</code> by executing a
254 * synchronized static method of that class.
255 * </ul>
256 * <p>
257 * Only one thread at a time can own an object's monitor.
258 *
259 * @exception IllegalMonitorStateException if the current thread is not
260 * the owner of this object's monitor.
261 * @see java.lang.Object#notifyAll()
262 * @see java.lang.Object#wait()
263 */
264 public final native void notify();
265
266 /**
267 * Wakes up all threads that are waiting on this object's monitor. A
268 * thread waits on an object's monitor by calling one of the
269 * <code>wait</code> methods.
270 * <p>
271 * The awakened threads will not be able to proceed until the current
272 * thread relinquishes the lock on this object. The awakened threads
273 * will compete in the usual manner with any other threads that might
274 * be actively competing to synchronize on this object; for example,
275 * the awakened threads enjoy no reliable privilege or disadvantage in
276 * being the next thread to lock this object.
277 * <p>
278 * This method should only be called by a thread that is the owner
279 * of this object's monitor. See the <code>notify</code> method for a
280 * description of the ways in which a thread can become the owner of
281 * a monitor.
282 *
283 * @exception IllegalMonitorStateException if the current thread is not
284 * the owner of this object's monitor.
285 * @see java.lang.Object#notify()
286 * @see java.lang.Object#wait()
287 */
288 public final native void notifyAll();
289
290 /**
291 * Causes current thread to wait until either another thread invokes the
292 * {@link java.lang.Object#notify()} method or the
293 * {@link java.lang.Object#notifyAll()} method for this object, or a
294 * specified amount of time has elapsed.
295 * <p>
296 * The current thread must own this object's monitor.
297 * <p>
298 * This method causes the current thread (call it <var>T</var>) to
299 * place itself in the wait set for this object and then to relinquish
300 * any and all synchronization claims on this object. Thread <var>T</var>
301 * becomes disabled for thread scheduling purposes and lies dormant
302 * until one of four things happens:
303 * <ul>
304 * <li>Some other thread invokes the <tt>notify</tt> method for this
305 * object and thread <var>T</var> happens to be arbitrarily chosen as
306 * the thread to be awakened.
307 * <li>Some other thread invokes the <tt>notifyAll</tt> method for this
308 * object.
309 * <li>Some other thread {@link java.lang.Thread#interrupt() interrupts}
310 * thread <var>T</var>.
311 * <li>The specified amount of real time has elapsed, more or less. If
312 * <tt>timeout</tt> is zero, however, then real time is not taken into
313 * consideration and the thread simply waits until notified.
314 * </ul>
315 * The thread <var>T</var> is then removed from the wait set for this
316 * object and re-enabled for thread scheduling. It then competes in the
317 * usual manner with other threads for the right to synchronize on the
318 * object; once it has gained control of the object, all its
319 * synchronization claims on the object are restored to the status quo
320 * ante - that is, to the situation as of the time that the <tt>wait</tt>
321 * method was invoked. Thread <var>T</var> then returns from the
322 * invocation of the <tt>wait</tt> method. Thus, on return from the
323 * <tt>wait</tt> method, the synchronization state of the object and of
324 * thread <tt>T</tt> is exactly as it was when the <tt>wait</tt> method
325 * was invoked.
326 * <p>
327 * A thread can also wake up without being notified, interrupted, or
328 * timing out, a so-called <i>spurious wakeup</i>. While this will rarely
329 * occur in practice, applications must guard against it by testing for
330 * the condition that should have caused the thread to be awakened, and
331 * continuing to wait if the condition is not satisfied. In other words,
332 * waits should always occur in loops, like this one:
333 * <pre>
334 * synchronized (obj) {
335 * while (<condition does not hold>)
336 * obj.wait(timeout);
337 * ... // Perform action appropriate to condition
338 * }
339 * </pre>
340 * (For more information on this topic, see Section 3.2.3 in Doug Lea's
341 * "Concurrent Programming in Java (Second Edition)" (Addison-Wesley,
342 * 2000), or Item 50 in Joshua Bloch's "Effective Java Programming
343 * Language Guide" (Addison-Wesley, 2001).
344 * <p>
345 * If the current thread is
346 * {@link java.lang.Thread#interrupt() interrupted} by another thread
347 * while it is waiting, then an <tt>InterruptedException</tt> is thrown.
348 * This exception is not thrown until the lock status of this object has
349 * been restored as described above.
350 * <p>
351 * Note that the <tt>wait</tt> method, as it places the current thread
352 * into the wait set for this object, unlocks only this object; any
353 * other objects on which the current thread may be synchronized remain
354 * locked while the thread waits.
355 * <p>
356 * This method should only be called by a thread that is the owner
357 * of this object's monitor. See the <code>notify</code> method for a
358 * description of the ways in which a thread can become the owner of
359 * a monitor.
360 *
361 * @param timeout the maximum time to wait in milliseconds.
362 * @exception IllegalArgumentException if the value of timeout is
363 * negative.
364 * @exception IllegalMonitorStateException if the current thread is not
365 * the owner of the object's monitor.
366 * @exception InterruptedException if another thread interrupted the
367 * current thread before or while the current thread
368 * was waiting for a notification. The <i>interrupted
369 * status</i> of the current thread is cleared when
370 * this exception is thrown.
371 * @see java.lang.Object#notify()
372 * @see java.lang.Object#notifyAll()
373 */
374 public final native void wait(long timeout) throws InterruptedException;
375
376 /**
377 * Causes current thread to wait until another thread invokes the
378 * {@link java.lang.Object#notify()} method or the
379 * {@link java.lang.Object#notifyAll()} method for this object, or
380 * some other thread interrupts the current thread, or a certain
381 * amount of real time has elapsed.
382 * <p>
383 * This method is similar to the <code>wait</code> method of one
384 * argument, but it allows finer control over the amount of time to
385 * wait for a notification before giving up. The amount of real time,
386 * measured in nanoseconds, is given by:
387 * <blockquote>
388 * <pre>
389 * 1000000*timeout+nanos</pre></blockquote>
390 * <p>
391 * In all other respects, this method does the same thing as the
392 * method {@link #wait(long)} of one argument. In particular,
393 * <tt>wait(0, 0)</tt> means the same thing as <tt>wait(0)</tt>.
394 * <p>
395 * The current thread must own this object's monitor. The thread
396 * releases ownership of this monitor and waits until either of the
397 * following two conditions has occurred:
398 * <ul>
399 * <li>Another thread notifies threads waiting on this object's monitor
400 * to wake up either through a call to the <code>notify</code> method
401 * or the <code>notifyAll</code> method.
402 * <li>The timeout period, specified by <code>timeout</code>
403 * milliseconds plus <code>nanos</code> nanoseconds arguments, has
404 * elapsed.
405 * </ul>
406 * <p>
407 * The thread then waits until it can re-obtain ownership of the
408 * monitor and resumes execution.
409 * <p>
410 * As in the one argument version, interrupts and spurious wakeups are
411 * possible, and this method should always be used in a loop:
412 * <pre>
413 * synchronized (obj) {
414 * while (<condition does not hold>)
415 * obj.wait(timeout, nanos);
416 * ... // Perform action appropriate to condition
417 * }
418 * </pre>
419 * This method should only be called by a thread that is the owner
420 * of this object's monitor. See the <code>notify</code> method for a
421 * description of the ways in which a thread can become the owner of
422 * a monitor.
423 *
424 * @param timeout the maximum time to wait in milliseconds.
425 * @param nanos additional time, in nanoseconds range
426 * 0-999999.
427 * @exception IllegalArgumentException if the value of timeout is
428 * negative or the value of nanos is
429 * not in the range 0-999999.
430 * @exception IllegalMonitorStateException if the current thread is not
431 * the owner of this object's monitor.
432 * @exception InterruptedException if another thread interrupted the
433 * current thread before or while the current thread
434 * was waiting for a notification. The <i>interrupted
435 * status</i> of the current thread is cleared when
436 * this exception is thrown.
437 */
438 public final void wait(long timeout, int nanos) throws InterruptedException {
439
440 bi04t002a.instrInvoke(bi04t002a.INSTR_WAIT_JI);
441
442 if (timeout < 0) {
443 throw new IllegalArgumentException("timeout value is negative");
444 }
445
446 if (nanos < 0 || nanos > 999999) {
447 throw new IllegalArgumentException(
448 "nanosecond timeout value out of range");
449 }
450
451 if (nanos >= 500000 || (nanos != 0 && timeout == 0)) {
452 timeout++;
453 }
454
455 wait(timeout);
456 }
457
458 /**
459 * Causes current thread to wait until another thread invokes the
460 * {@link java.lang.Object#notify()} method or the
461 * {@link java.lang.Object#notifyAll()} method for this object.
462 * In other words, this method behaves exactly as if it simply
463 * performs the call <tt>wait(0)</tt>.
464 * <p>
465 * The current thread must own this object's monitor. The thread
466 * releases ownership of this monitor and waits until another thread
467 * notifies threads waiting on this object's monitor to wake up
468 * either through a call to the <code>notify</code> method or the
469 * <code>notifyAll</code> method. The thread then waits until it can
470 * re-obtain ownership of the monitor and resumes execution.
471 * <p>
472 * As in the one argument version, interrupts and spurious wakeups are
473 * possible, and this method should always be used in a loop:
474 * <pre>
475 * synchronized (obj) {
476 * while (<condition does not hold>)
477 * obj.wait();
478 * ... // Perform action appropriate to condition
479 * }
480 * </pre>
481 * This method should only be called by a thread that is the owner
482 * of this object's monitor. See the <code>notify</code> method for a
483 * description of the ways in which a thread can become the owner of
484 * a monitor.
485 *
486 * @exception IllegalMonitorStateException if the current thread is not
487 * the owner of the object's monitor.
488 * @exception InterruptedException if another thread interrupted the
489 * current thread before or while the current thread
490 * was waiting for a notification. The <i>interrupted
491 * status</i> of the current thread is cleared when
492 * this exception is thrown.
493 * @see java.lang.Object#notify()
494 * @see java.lang.Object#notifyAll()
495 */
496 public final void wait() throws InterruptedException {
497 bi04t002a.instrInvoke(bi04t002a.INSTR_WAIT);
498 wait(0);
499 }
500
501 /**
502 * Called by the garbage collector on an object when garbage collection
503 * determines that there are no more references to the object.
504 * A subclass overrides the <code>finalize</code> method to dispose of
505 * system resources or to perform other cleanup.
506 * <p>
507 * The general contract of <tt>finalize</tt> is that it is invoked
508 * if and when the Java<font size="-2"><sup>TM</sup></font> virtual
509 * machine has determined that there is no longer any
510 * means by which this object can be accessed by any thread that has
511 * not yet died, except as a result of an action taken by the
512 * finalization of some other object or class which is ready to be
513 * finalized. The <tt>finalize</tt> method may take any action, including
514 * making this object available again to other threads; the usual purpose
515 * of <tt>finalize</tt>, however, is to perform cleanup actions before
516 * the object is irrevocably discarded. For example, the finalize method
517 * for an object that represents an input/output connection might perform
518 * explicit I/O transactions to break the connection before the object is
519 * permanently discarded.
520 * <p>
521 * The <tt>finalize</tt> method of class <tt>Object</tt> performs no
522 * special action; it simply returns normally. Subclasses of
523 * <tt>Object</tt> may override this definition.
524 * <p>
525 * The Java programming language does not guarantee which thread will
526 * invoke the <tt>finalize</tt> method for any given object. It is
527 * guaranteed, however, that the thread that invokes finalize will not
528 * be holding any user-visible synchronization locks when finalize is
529 * invoked. If an uncaught exception is thrown by the finalize method,
530 * the exception is ignored and finalization of that object terminates.
531 * <p>
532 * After the <tt>finalize</tt> method has been invoked for an object, no
533 * further action is taken until the Java virtual machine has again
534 * determined that there is no longer any means by which this object can
535 * be accessed by any thread that has not yet died, including possible
536 * actions by other objects or classes which are ready to be finalized,
537 * at which point the object may be discarded.
538 * <p>
539 * The <tt>finalize</tt> method is never invoked more than once by a Java
540 * virtual machine for any given object.
541 * <p>
542 * Any exception thrown by the <code>finalize</code> method causes
543 * the finalization of this object to be halted, but is otherwise
544 * ignored.
545 *
546 * @throws Throwable the <code>Exception</code> raised by this method
547 */
548 protected void finalize() throws Throwable { }
549
550 }