1 /*
2 * Copyright (c) 1994, 2013, 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 java.lang.ref.Reference;
29 import java.lang.ref.ReferenceQueue;
30 import java.lang.ref.WeakReference;
31 import java.security.AccessController;
32 import java.security.AccessControlContext;
33 import java.security.PrivilegedAction;
34 import java.util.Map;
35 import java.util.HashMap;
36 import java.util.concurrent.ConcurrentHashMap;
37 import java.util.concurrent.ConcurrentMap;
38 import java.util.concurrent.locks.LockSupport;
39 import sun.nio.ch.Interruptible;
40 import sun.reflect.CallerSensitive;
41 import sun.reflect.Reflection;
42 import sun.security.util.SecurityConstants;
43 import jdk.internal.HotSpotIntrinsicCandidate;
44
45 /**
46 * A <i>thread</i> is a thread of execution in a program. The Java
47 * Virtual Machine allows an application to have multiple threads of
48 * execution running concurrently.
49 * <p>
50 * Every thread has a priority. Threads with higher priority are
51 * executed in preference to threads with lower priority. Each thread
52 * may or may not also be marked as a daemon. When code running in
53 * some thread creates a new <code>Thread</code> object, the new
54 * thread has its priority initially set equal to the priority of the
55 * creating thread, and is a daemon thread if and only if the
56 * creating thread is a daemon.
57 * <p>
58 * When a Java Virtual Machine starts up, there is usually a single
59 * non-daemon thread (which typically calls the method named
60 * <code>main</code> of some designated class). The Java Virtual
61 * Machine continues to execute threads until either of the following
62 * occurs:
63 * <ul>
64 * <li>The <code>exit</code> method of class <code>Runtime</code> has been
65 * called and the security manager has permitted the exit operation
66 * to take place.
67 * <li>All threads that are not daemon threads have died, either by
68 * returning from the call to the <code>run</code> method or by
69 * throwing an exception that propagates beyond the <code>run</code>
70 * method.
71 * </ul>
72 * <p>
73 * There are two ways to create a new thread of execution. One is to
74 * declare a class to be a subclass of <code>Thread</code>. This
75 * subclass should override the <code>run</code> method of class
76 * <code>Thread</code>. An instance of the subclass can then be
77 * allocated and started. For example, a thread that computes primes
78 * larger than a stated value could be written as follows:
79 * <hr><blockquote><pre>
80 * class PrimeThread extends Thread {
81 * long minPrime;
82 * PrimeThread(long minPrime) {
83 * this.minPrime = minPrime;
84 * }
85 *
86 * public void run() {
87 * // compute primes larger than minPrime
88 * . . .
89 * }
90 * }
91 * </pre></blockquote><hr>
92 * <p>
93 * The following code would then create a thread and start it running:
94 * <blockquote><pre>
95 * PrimeThread p = new PrimeThread(143);
96 * p.start();
97 * </pre></blockquote>
98 * <p>
99 * The other way to create a thread is to declare a class that
100 * implements the <code>Runnable</code> interface. That class then
101 * implements the <code>run</code> method. An instance of the class can
102 * then be allocated, passed as an argument when creating
103 * <code>Thread</code>, and started. The same example in this other
104 * style looks like the following:
105 * <hr><blockquote><pre>
106 * class PrimeRun implements Runnable {
107 * long minPrime;
108 * PrimeRun(long minPrime) {
109 * this.minPrime = minPrime;
110 * }
111 *
112 * public void run() {
113 * // compute primes larger than minPrime
114 * . . .
115 * }
116 * }
117 * </pre></blockquote><hr>
118 * <p>
119 * The following code would then create a thread and start it running:
120 * <blockquote><pre>
121 * PrimeRun p = new PrimeRun(143);
122 * new Thread(p).start();
123 * </pre></blockquote>
124 * <p>
125 * Every thread has a name for identification purposes. More than
126 * one thread may have the same name. If a name is not specified when
127 * a thread is created, a new name is generated for it.
128 * <p>
129 * Unless otherwise noted, passing a {@code null} argument to a constructor
130 * or method in this class will cause a {@link NullPointerException} to be
131 * thrown.
132 *
133 * @author unascribed
134 * @see Runnable
135 * @see Runtime#exit(int)
136 * @see #run()
137 * @see #stop()
138 * @since 1.0
139 */
140 public
141 class Thread implements Runnable {
142 /* Make sure registerNatives is the first thing <clinit> does. */
143 private static native void registerNatives();
144 static {
145 registerNatives();
146 }
147
148 private volatile String name;
149 private int priority;
150 private Thread threadQ;
151 private long eetop;
152
153 /* Whether or not to single_step this thread. */
154 private boolean single_step;
155
156 /* Whether or not the thread is a daemon thread. */
157 private boolean daemon = false;
158
159 /* JVM state */
160 private boolean stillborn = false;
161
162 /* What will be run. */
163 private Runnable target;
164
165 /* The group of this thread */
166 private ThreadGroup group;
167
168 /* The context ClassLoader for this thread */
169 private ClassLoader contextClassLoader;
170
171 /* The inherited AccessControlContext of this thread */
172 private AccessControlContext inheritedAccessControlContext;
173
174 /* For autonumbering anonymous threads. */
175 private static int threadInitNumber;
176 private static synchronized int nextThreadNum() {
177 return threadInitNumber++;
178 }
179
180 /* ThreadLocal values pertaining to this thread. This map is maintained
181 * by the ThreadLocal class. */
182 ThreadLocal.ThreadLocalMap threadLocals = null;
183
184 /*
185 * InheritableThreadLocal values pertaining to this thread. This map is
186 * maintained by the InheritableThreadLocal class.
187 */
188 ThreadLocal.ThreadLocalMap inheritableThreadLocals = null;
189
190 /*
191 * The requested stack size for this thread, or 0 if the creator did
192 * not specify a stack size. It is up to the VM to do whatever it
193 * likes with this number; some VMs will ignore it.
194 */
195 private long stackSize;
196
197 /*
198 * JVM-private state that persists after native thread termination.
199 */
200 private long nativeParkEventPointer;
201
202 /*
203 * Thread ID
204 */
205 private long tid;
206
207 /* For generating thread ID */
208 private static long threadSeqNumber;
209
210 /*
211 * Java thread status for tools, default indicates thread 'not yet started'
212 */
213 private volatile int threadStatus;
214
215 private static synchronized long nextThreadID() {
216 return ++threadSeqNumber;
217 }
218
219 /**
220 * The argument supplied to the current call to
221 * java.util.concurrent.locks.LockSupport.park.
222 * Set by (private) java.util.concurrent.locks.LockSupport.setBlocker
223 * Accessed using java.util.concurrent.locks.LockSupport.getBlocker
224 */
225 volatile Object parkBlocker;
226
227 /* The object in which this thread is blocked in an interruptible I/O
228 * operation, if any. The blocker's interrupt method should be invoked
229 * after setting this thread's interrupt status.
230 */
231 private volatile Interruptible blocker;
232 private final Object blockerLock = new Object();
233
234 /* Set the blocker field; invoked via jdk.internal.misc.SharedSecrets
235 * from java.nio code
236 */
237 void blockedOn(Interruptible b) {
238 synchronized (blockerLock) {
239 blocker = b;
240 }
241 }
242
243 /**
244 * The minimum priority that a thread can have.
245 */
246 public static final int MIN_PRIORITY = 1;
247
248 /**
249 * The default priority that is assigned to a thread.
250 */
251 public static final int NORM_PRIORITY = 5;
252
253 /**
254 * The maximum priority that a thread can have.
255 */
256 public static final int MAX_PRIORITY = 10;
257
258 /**
259 * Returns a reference to the currently executing thread object.
260 *
261 * @return the currently executing thread.
262 */
263 @HotSpotIntrinsicCandidate
264 public static native Thread currentThread();
265
266 /**
267 * A hint to the scheduler that the current thread is willing to yield
268 * its current use of a processor. The scheduler is free to ignore this
269 * hint.
270 *
271 * <p> Yield is a heuristic attempt to improve relative progression
272 * between threads that would otherwise over-utilise a CPU. Its use
273 * should be combined with detailed profiling and benchmarking to
274 * ensure that it actually has the desired effect.
275 *
276 * <p> It is rarely appropriate to use this method. It may be useful
277 * for debugging or testing purposes, where it may help to reproduce
278 * bugs due to race conditions. It may also be useful when designing
279 * concurrency control constructs such as the ones in the
280 * {@link java.util.concurrent.locks} package.
281 */
282 public static native void yield();
283
284 /**
285 * Causes the currently executing thread to sleep (temporarily cease
286 * execution) for the specified number of milliseconds, subject to
287 * the precision and accuracy of system timers and schedulers. The thread
288 * does not lose ownership of any monitors.
289 *
290 * @param millis
291 * the length of time to sleep in milliseconds
292 *
293 * @throws IllegalArgumentException
294 * if the value of {@code millis} is negative
295 *
296 * @throws InterruptedException
297 * if any thread has interrupted the current thread. The
298 * <i>interrupted status</i> of the current thread is
299 * cleared when this exception is thrown.
300 */
301 public static native void sleep(long millis) throws InterruptedException;
302
303 /**
304 * Causes the currently executing thread to sleep (temporarily cease
305 * execution) for the specified number of milliseconds plus the specified
306 * number of nanoseconds, subject to the precision and accuracy of system
307 * timers and schedulers. The thread does not lose ownership of any
308 * monitors.
309 *
310 * @param millis
311 * the length of time to sleep in milliseconds
312 *
313 * @param nanos
314 * {@code 0-999999} additional nanoseconds to sleep
315 *
316 * @throws IllegalArgumentException
317 * if the value of {@code millis} is negative, or the value of
318 * {@code nanos} is not in the range {@code 0-999999}
319 *
320 * @throws InterruptedException
321 * if any thread has interrupted the current thread. The
322 * <i>interrupted status</i> of the current thread is
323 * cleared when this exception is thrown.
324 */
325 public static void sleep(long millis, int nanos)
326 throws InterruptedException {
327 if (millis < 0) {
328 throw new IllegalArgumentException("timeout value is negative");
329 }
330
331 if (nanos < 0 || nanos > 999999) {
332 throw new IllegalArgumentException(
333 "nanosecond timeout value out of range");
334 }
335
336 if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
337 millis++;
338 }
339
340 sleep(millis);
341 }
342
343 /**
344 * Initializes a Thread with the current AccessControlContext.
345 * @see #init(ThreadGroup,Runnable,String,long,AccessControlContext,boolean)
346 */
347 private void init(ThreadGroup g, Runnable target, String name,
348 long stackSize) {
349 init(g, target, name, stackSize, null, true);
350 }
351
352 /**
353 * Initializes a Thread.
354 *
355 * @param g the Thread group
356 * @param target the object whose run() method gets called
357 * @param name the name of the new Thread
358 * @param stackSize the desired stack size for the new thread, or
359 * zero to indicate that this parameter is to be ignored.
360 * @param acc the AccessControlContext to inherit, or
361 * AccessController.getContext() if null
362 * @param inheritThreadLocals if {@code true}, inherit initial values for
363 * inheritable thread-locals from the constructing thread
364 */
365 private void init(ThreadGroup g, Runnable target, String name,
366 long stackSize, AccessControlContext acc,
367 boolean inheritThreadLocals) {
368 if (name == null) {
369 throw new NullPointerException("name cannot be null");
370 }
371
372 this.name = name;
373
374 Thread parent = currentThread();
375 SecurityManager security = System.getSecurityManager();
376 if (g == null) {
377 /* Determine if it's an applet or not */
378
379 /* If there is a security manager, ask the security manager
380 what to do. */
381 if (security != null) {
382 g = security.getThreadGroup();
383 }
384
385 /* If the security doesn't have a strong opinion of the matter
386 use the parent thread group. */
387 if (g == null) {
388 g = parent.getThreadGroup();
389 }
390 }
391
392 /* checkAccess regardless of whether or not threadgroup is
393 explicitly passed in. */
394 g.checkAccess();
395
396 /*
397 * Do we have the required permissions?
398 */
399 if (security != null) {
400 if (isCCLOverridden(getClass())) {
401 security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
402 }
403 }
404
405 g.addUnstarted();
406
407 this.group = g;
408 this.daemon = parent.isDaemon();
409 this.priority = parent.getPriority();
410 if (security == null || isCCLOverridden(parent.getClass()))
411 this.contextClassLoader = parent.getContextClassLoader();
412 else
413 this.contextClassLoader = parent.contextClassLoader;
414 this.inheritedAccessControlContext =
415 acc != null ? acc : AccessController.getContext();
416 this.target = target;
417 setPriority(priority);
418 if (inheritThreadLocals && parent.inheritableThreadLocals != null)
419 this.inheritableThreadLocals =
420 ThreadLocal.createInheritedMap(parent.inheritableThreadLocals);
421 /* Stash the specified stack size in case the VM cares */
422 this.stackSize = stackSize;
423
424 /* Set thread ID */
425 tid = nextThreadID();
426 }
427
428 /**
429 * Throws CloneNotSupportedException as a Thread can not be meaningfully
430 * cloned. Construct a new Thread instead.
431 *
432 * @throws CloneNotSupportedException
433 * always
434 */
435 @Override
436 protected Object clone() throws CloneNotSupportedException {
437 throw new CloneNotSupportedException();
438 }
439
440 /**
441 * Allocates a new {@code Thread} object. This constructor has the same
442 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
443 * {@code (null, null, gname)}, where {@code gname} is a newly generated
444 * name. Automatically generated names are of the form
445 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
446 */
447 public Thread() {
448 init(null, null, "Thread-" + nextThreadNum(), 0);
449 }
450
451 /**
452 * Allocates a new {@code Thread} object. This constructor has the same
453 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
454 * {@code (null, target, gname)}, where {@code gname} is a newly generated
455 * name. Automatically generated names are of the form
456 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
457 *
458 * @param target
459 * the object whose {@code run} method is invoked when this thread
460 * is started. If {@code null}, this classes {@code run} method does
461 * nothing.
462 */
463 public Thread(Runnable target) {
464 init(null, target, "Thread-" + nextThreadNum(), 0);
465 }
466
467 /**
468 * Creates a new Thread that inherits the given AccessControlContext.
469 * This is not a public constructor.
470 */
471 Thread(Runnable target, AccessControlContext acc) {
472 init(null, target, "Thread-" + nextThreadNum(), 0, acc, true);
473 }
474
475 /**
476 * Allocates a new {@code Thread} object. This constructor has the same
477 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
478 * {@code (group, target, gname)} ,where {@code gname} is a newly generated
479 * name. Automatically generated names are of the form
480 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
481 *
482 * @param group
483 * the thread group. If {@code null} and there is a security
484 * manager, the group is determined by {@linkplain
485 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
486 * If there is not a security manager or {@code
487 * SecurityManager.getThreadGroup()} returns {@code null}, the group
488 * is set to the current thread's thread group.
489 *
490 * @param target
491 * the object whose {@code run} method is invoked when this thread
492 * is started. If {@code null}, this thread's run method is invoked.
493 *
494 * @throws SecurityException
495 * if the current thread cannot create a thread in the specified
496 * thread group
497 */
498 public Thread(ThreadGroup group, Runnable target) {
499 init(group, target, "Thread-" + nextThreadNum(), 0);
500 }
501
502 /**
503 * Allocates a new {@code Thread} object. This constructor has the same
504 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
505 * {@code (null, null, name)}.
506 *
507 * @param name
508 * the name of the new thread
509 */
510 public Thread(String name) {
511 init(null, null, name, 0);
512 }
513
514 /**
515 * Allocates a new {@code Thread} object. This constructor has the same
516 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
517 * {@code (group, null, name)}.
518 *
519 * @param group
520 * the thread group. If {@code null} and there is a security
521 * manager, the group is determined by {@linkplain
522 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
523 * If there is not a security manager or {@code
524 * SecurityManager.getThreadGroup()} returns {@code null}, the group
525 * is set to the current thread's thread group.
526 *
527 * @param name
528 * the name of the new thread
529 *
530 * @throws SecurityException
531 * if the current thread cannot create a thread in the specified
532 * thread group
533 */
534 public Thread(ThreadGroup group, String name) {
535 init(group, null, name, 0);
536 }
537
538 /**
539 * Allocates a new {@code Thread} object. This constructor has the same
540 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
541 * {@code (null, target, name)}.
542 *
543 * @param target
544 * the object whose {@code run} method is invoked when this thread
545 * is started. If {@code null}, this thread's run method is invoked.
546 *
547 * @param name
548 * the name of the new thread
549 */
550 public Thread(Runnable target, String name) {
551 init(null, target, name, 0);
552 }
553
554 /**
555 * Allocates a new {@code Thread} object so that it has {@code target}
556 * as its run object, has the specified {@code name} as its name,
557 * and belongs to the thread group referred to by {@code group}.
558 *
559 * <p>If there is a security manager, its
560 * {@link SecurityManager#checkAccess(ThreadGroup) checkAccess}
561 * method is invoked with the ThreadGroup as its argument.
562 *
563 * <p>In addition, its {@code checkPermission} method is invoked with
564 * the {@code RuntimePermission("enableContextClassLoaderOverride")}
565 * permission when invoked directly or indirectly by the constructor
566 * of a subclass which overrides the {@code getContextClassLoader}
567 * or {@code setContextClassLoader} methods.
568 *
569 * <p>The priority of the newly created thread is set equal to the
570 * priority of the thread creating it, that is, the currently running
571 * thread. The method {@linkplain #setPriority setPriority} may be
572 * used to change the priority to a new value.
573 *
574 * <p>The newly created thread is initially marked as being a daemon
575 * thread if and only if the thread creating it is currently marked
576 * as a daemon thread. The method {@linkplain #setDaemon setDaemon}
577 * may be used to change whether or not a thread is a daemon.
578 *
579 * @param group
580 * the thread group. If {@code null} and there is a security
581 * manager, the group is determined by {@linkplain
582 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
583 * If there is not a security manager or {@code
584 * SecurityManager.getThreadGroup()} returns {@code null}, the group
585 * is set to the current thread's thread group.
586 *
587 * @param target
588 * the object whose {@code run} method is invoked when this thread
589 * is started. If {@code null}, this thread's run method is invoked.
590 *
591 * @param name
592 * the name of the new thread
593 *
594 * @throws SecurityException
595 * if the current thread cannot create a thread in the specified
596 * thread group or cannot override the context class loader methods.
597 */
598 public Thread(ThreadGroup group, Runnable target, String name) {
599 init(group, target, name, 0);
600 }
601
602 /**
603 * Allocates a new {@code Thread} object so that it has {@code target}
604 * as its run object, has the specified {@code name} as its name,
605 * and belongs to the thread group referred to by {@code group}, and has
606 * the specified <i>stack size</i>.
607 *
608 * <p>This constructor is identical to {@link
609 * #Thread(ThreadGroup,Runnable,String)} with the exception of the fact
610 * that it allows the thread stack size to be specified. The stack size
611 * is the approximate number of bytes of address space that the virtual
612 * machine is to allocate for this thread's stack. <b>The effect of the
613 * {@code stackSize} parameter, if any, is highly platform dependent.</b>
614 *
615 * <p>On some platforms, specifying a higher value for the
616 * {@code stackSize} parameter may allow a thread to achieve greater
617 * recursion depth before throwing a {@link StackOverflowError}.
618 * Similarly, specifying a lower value may allow a greater number of
619 * threads to exist concurrently without throwing an {@link
620 * OutOfMemoryError} (or other internal error). The details of
621 * the relationship between the value of the {@code stackSize} parameter
622 * and the maximum recursion depth and concurrency level are
623 * platform-dependent. <b>On some platforms, the value of the
624 * {@code stackSize} parameter may have no effect whatsoever.</b>
625 *
626 * <p>The virtual machine is free to treat the {@code stackSize}
627 * parameter as a suggestion. If the specified value is unreasonably low
628 * for the platform, the virtual machine may instead use some
629 * platform-specific minimum value; if the specified value is unreasonably
630 * high, the virtual machine may instead use some platform-specific
631 * maximum. Likewise, the virtual machine is free to round the specified
632 * value up or down as it sees fit (or to ignore it completely).
633 *
634 * <p>Specifying a value of zero for the {@code stackSize} parameter will
635 * cause this constructor to behave exactly like the
636 * {@code Thread(ThreadGroup, Runnable, String)} constructor.
637 *
638 * <p><i>Due to the platform-dependent nature of the behavior of this
639 * constructor, extreme care should be exercised in its use.
640 * The thread stack size necessary to perform a given computation will
641 * likely vary from one JRE implementation to another. In light of this
642 * variation, careful tuning of the stack size parameter may be required,
643 * and the tuning may need to be repeated for each JRE implementation on
644 * which an application is to run.</i>
645 *
646 * <p>Implementation note: Java platform implementers are encouraged to
647 * document their implementation's behavior with respect to the
648 * {@code stackSize} parameter.
649 *
650 *
651 * @param group
652 * the thread group. If {@code null} and there is a security
653 * manager, the group is determined by {@linkplain
654 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
655 * If there is not a security manager or {@code
656 * SecurityManager.getThreadGroup()} returns {@code null}, the group
657 * is set to the current thread's thread group.
658 *
659 * @param target
660 * the object whose {@code run} method is invoked when this thread
661 * is started. If {@code null}, this thread's run method is invoked.
662 *
663 * @param name
664 * the name of the new thread
665 *
666 * @param stackSize
667 * the desired stack size for the new thread, or zero to indicate
668 * that this parameter is to be ignored.
669 *
670 * @throws SecurityException
671 * if the current thread cannot create a thread in the specified
672 * thread group
673 *
674 * @since 1.4
675 */
676 public Thread(ThreadGroup group, Runnable target, String name,
677 long stackSize) {
678 init(group, target, name, stackSize);
679 }
680
681 /**
682 * Allocates a new {@code Thread} object so that it has {@code target}
683 * as its run object, has the specified {@code name} as its name,
684 * belongs to the thread group referred to by {@code group}, has
685 * the specified {@code stackSize}, and inherits initial values for
686 * {@linkplain InheritableThreadLocal inheritable thread-local} variables
687 * if {@code inheritThreadLocals} is {@code true}.
688 *
689 * <p> This constructor is identical to {@link
690 * #Thread(ThreadGroup,Runnable,String,long)} with the added ability to
691 * suppress, or not, the inheriting of initial values for inheritable
692 * thread-local variables from the constructing thread. This allows for
693 * finer grain control over inheritable thread-locals. Care must be taken
694 * when passing a value of {@code false} for {@code inheritThreadLocals},
695 * as it may lead to unexpected behavior if the new thread executes code
696 * that expects a specific thread-local value to be inherited.
697 *
698 * <p> Specifying a value of {@code true} for the {@code inheritThreadLocals}
699 * parameter will cause this constructor to behave exactly like the
700 * {@code Thread(ThreadGroup, Runnable, String, long)} constructor.
701 *
702 * @param group
703 * the thread group. If {@code null} and there is a security
704 * manager, the group is determined by {@linkplain
705 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
706 * If there is not a security manager or {@code
707 * SecurityManager.getThreadGroup()} returns {@code null}, the group
708 * is set to the current thread's thread group.
709 *
710 * @param target
711 * the object whose {@code run} method is invoked when this thread
712 * is started. If {@code null}, this thread's run method is invoked.
713 *
714 * @param name
715 * the name of the new thread
716 *
717 * @param stackSize
718 * the desired stack size for the new thread, or zero to indicate
719 * that this parameter is to be ignored
720 *
721 * @param inheritThreadLocals
722 * if {@code true}, inherit initial values for inheritable
723 * thread-locals from the constructing thread, otherwise no initial
724 * values are inherited
725 *
726 * @throws SecurityException
727 * if the current thread cannot create a thread in the specified
728 * thread group
729 *
730 * @since 9
731 */
732 public Thread(ThreadGroup group, Runnable target, String name,
733 long stackSize, boolean inheritThreadLocals) {
734 init(group, target, name, stackSize, null, inheritThreadLocals);
735 }
736
737 /**
738 * Causes this thread to begin execution; the Java Virtual Machine
739 * calls the <code>run</code> method of this thread.
740 * <p>
741 * The result is that two threads are running concurrently: the
742 * current thread (which returns from the call to the
743 * <code>start</code> method) and the other thread (which executes its
744 * <code>run</code> method).
745 * <p>
746 * It is never legal to start a thread more than once.
747 * In particular, a thread may not be restarted once it has completed
748 * execution.
749 *
750 * @exception IllegalThreadStateException if the thread was already
751 * started.
752 * @see #run()
753 * @see #stop()
754 */
755 public synchronized void start() {
756 /**
757 * This method is not invoked for the main method thread or "system"
758 * group threads created/set up by the VM. Any new functionality added
759 * to this method in the future may have to also be added to the VM.
760 *
761 * A zero status value corresponds to state "NEW".
762 */
763 if (threadStatus != 0)
764 throw new IllegalThreadStateException();
765
766 /* Notify the group that this thread is about to be started
767 * so that it can be added to the group's list of threads
768 * and the group's unstarted count can be decremented. */
769 group.add(this);
770
771 boolean started = false;
772 try {
773 start0();
774 started = true;
775 } finally {
776 try {
777 if (!started) {
778 group.threadStartFailed(this);
779 }
780 } catch (Throwable ignore) {
781 /* do nothing. If start0 threw a Throwable then
782 it will be passed up the call stack */
783 }
784 }
785 }
786
787 private native void start0();
788
789 /**
790 * If this thread was constructed using a separate
791 * <code>Runnable</code> run object, then that
792 * <code>Runnable</code> object's <code>run</code> method is called;
793 * otherwise, this method does nothing and returns.
794 * <p>
795 * Subclasses of <code>Thread</code> should override this method.
796 *
797 * @see #start()
798 * @see #stop()
799 * @see #Thread(ThreadGroup, Runnable, String)
800 */
801 @Override
802 public void run() {
803 if (target != null) {
804 target.run();
805 }
806 }
807
808 /**
809 * This method is called by the system to give a Thread
810 * a chance to clean up before it actually exits.
811 */
812 private void exit() {
813 if (group != null) {
814 group.threadTerminated(this);
815 group = null;
816 }
817 /* Aggressively null out all reference fields: see bug 4006245 */
818 target = null;
819 /* Speed the release of some of these resources */
820 threadLocals = null;
821 inheritableThreadLocals = null;
822 inheritedAccessControlContext = null;
823 blocker = null;
824 uncaughtExceptionHandler = null;
825 }
826
827 /**
828 * Forces the thread to stop executing.
829 * <p>
830 * If there is a security manager installed, its <code>checkAccess</code>
831 * method is called with <code>this</code>
832 * as its argument. This may result in a
833 * <code>SecurityException</code> being raised (in the current thread).
834 * <p>
835 * If this thread is different from the current thread (that is, the current
836 * thread is trying to stop a thread other than itself), the
837 * security manager's <code>checkPermission</code> method (with a
838 * <code>RuntimePermission("stopThread")</code> argument) is called in
839 * addition.
840 * Again, this may result in throwing a
841 * <code>SecurityException</code> (in the current thread).
842 * <p>
843 * The thread represented by this thread is forced to stop whatever
844 * it is doing abnormally and to throw a newly created
845 * <code>ThreadDeath</code> object as an exception.
846 * <p>
847 * It is permitted to stop a thread that has not yet been started.
848 * If the thread is eventually started, it immediately terminates.
849 * <p>
850 * An application should not normally try to catch
851 * <code>ThreadDeath</code> unless it must do some extraordinary
852 * cleanup operation (note that the throwing of
853 * <code>ThreadDeath</code> causes <code>finally</code> clauses of
854 * <code>try</code> statements to be executed before the thread
855 * officially dies). If a <code>catch</code> clause catches a
856 * <code>ThreadDeath</code> object, it is important to rethrow the
857 * object so that the thread actually dies.
858 * <p>
859 * The top-level error handler that reacts to otherwise uncaught
860 * exceptions does not print out a message or otherwise notify the
861 * application if the uncaught exception is an instance of
862 * <code>ThreadDeath</code>.
863 *
864 * @exception SecurityException if the current thread cannot
865 * modify this thread.
866 * @see #interrupt()
867 * @see #checkAccess()
868 * @see #run()
869 * @see #start()
870 * @see ThreadDeath
871 * @see ThreadGroup#uncaughtException(Thread,Throwable)
872 * @see SecurityManager#checkAccess(Thread)
873 * @see SecurityManager#checkPermission
874 * @deprecated This method is inherently unsafe. Stopping a thread with
875 * Thread.stop causes it to unlock all of the monitors that it
876 * has locked (as a natural consequence of the unchecked
877 * <code>ThreadDeath</code> exception propagating up the stack). If
878 * any of the objects previously protected by these monitors were in
879 * an inconsistent state, the damaged objects become visible to
880 * other threads, potentially resulting in arbitrary behavior. Many
881 * uses of <code>stop</code> should be replaced by code that simply
882 * modifies some variable to indicate that the target thread should
883 * stop running. The target thread should check this variable
884 * regularly, and return from its run method in an orderly fashion
885 * if the variable indicates that it is to stop running. If the
886 * target thread waits for long periods (on a condition variable,
887 * for example), the <code>interrupt</code> method should be used to
888 * interrupt the wait.
889 * For more information, see
890 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
891 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
892 */
893 @Deprecated
894 public final void stop() {
895 SecurityManager security = System.getSecurityManager();
896 if (security != null) {
897 checkAccess();
898 if (this != Thread.currentThread()) {
899 security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
900 }
901 }
902 // A zero status value corresponds to "NEW", it can't change to
903 // not-NEW because we hold the lock.
904 if (threadStatus != 0) {
905 resume(); // Wake up thread if it was suspended; no-op otherwise
906 }
907
908 // The VM can handle all thread states
909 stop0(new ThreadDeath());
910 }
911
912 /**
913 * Throws {@code UnsupportedOperationException}.
914 *
915 * @param obj ignored
916 *
917 * @deprecated This method was originally designed to force a thread to stop
918 * and throw a given {@code Throwable} as an exception. It was
919 * inherently unsafe (see {@link #stop()} for details), and furthermore
920 * could be used to generate exceptions that the target thread was
921 * not prepared to handle.
922 * For more information, see
923 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
924 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
925 */
926 @Deprecated
927 public final synchronized void stop(Throwable obj) {
928 throw new UnsupportedOperationException();
929 }
930
931 /**
932 * Interrupts this thread.
933 *
934 * <p> Unless the current thread is interrupting itself, which is
935 * always permitted, the {@link #checkAccess() checkAccess} method
936 * of this thread is invoked, which may cause a {@link
937 * SecurityException} to be thrown.
938 *
939 * <p> If this thread is blocked in an invocation of the {@link
940 * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
941 * Object#wait(long, int) wait(long, int)} methods of the {@link Object}
942 * class, or of the {@link #join()}, {@link #join(long)}, {@link
943 * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
944 * methods of this class, then its interrupt status will be cleared and it
945 * will receive an {@link InterruptedException}.
946 *
947 * <p> If this thread is blocked in an I/O operation upon an {@link
948 * java.nio.channels.InterruptibleChannel InterruptibleChannel}
949 * then the channel will be closed, the thread's interrupt
950 * status will be set, and the thread will receive a {@link
951 * java.nio.channels.ClosedByInterruptException}.
952 *
953 * <p> If this thread is blocked in a {@link java.nio.channels.Selector}
954 * then the thread's interrupt status will be set and it will return
955 * immediately from the selection operation, possibly with a non-zero
956 * value, just as if the selector's {@link
957 * java.nio.channels.Selector#wakeup wakeup} method were invoked.
958 *
959 * <p> If none of the previous conditions hold then this thread's interrupt
960 * status will be set. </p>
961 *
962 * <p> Interrupting a thread that is not alive need not have any effect.
963 *
964 * @throws SecurityException
965 * if the current thread cannot modify this thread
966 *
967 * @revised 6.0
968 * @spec JSR-51
969 */
970 public void interrupt() {
971 if (this != Thread.currentThread())
972 checkAccess();
973
974 synchronized (blockerLock) {
975 Interruptible b = blocker;
976 if (b != null) {
977 interrupt0(); // Just to set the interrupt flag
978 b.interrupt(this);
979 return;
980 }
981 }
982 interrupt0();
983 }
984
985 /**
986 * Tests whether the current thread has been interrupted. The
987 * <i>interrupted status</i> of the thread is cleared by this method. In
988 * other words, if this method were to be called twice in succession, the
989 * second call would return false (unless the current thread were
990 * interrupted again, after the first call had cleared its interrupted
991 * status and before the second call had examined it).
992 *
993 * <p>A thread interruption ignored because a thread was not alive
994 * at the time of the interrupt will be reflected by this method
995 * returning false.
996 *
997 * @return <code>true</code> if the current thread has been interrupted;
998 * <code>false</code> otherwise.
999 * @see #isInterrupted()
1000 * @revised 6.0
1001 */
1002 public static boolean interrupted() {
1003 return currentThread().isInterrupted(true);
1004 }
1005
1006 /**
1007 * Tests whether this thread has been interrupted. The <i>interrupted
1008 * status</i> of the thread is unaffected by this method.
1009 *
1010 * <p>A thread interruption ignored because a thread was not alive
1011 * at the time of the interrupt will be reflected by this method
1012 * returning false.
1013 *
1014 * @return <code>true</code> if this thread has been interrupted;
1015 * <code>false</code> otherwise.
1016 * @see #interrupted()
1017 * @revised 6.0
1018 */
1019 public boolean isInterrupted() {
1020 return isInterrupted(false);
1021 }
1022
1023 /**
1024 * Tests if some Thread has been interrupted. The interrupted state
1025 * is reset or not based on the value of ClearInterrupted that is
1026 * passed.
1027 */
1028 @HotSpotIntrinsicCandidate
1029 private native boolean isInterrupted(boolean ClearInterrupted);
1030
1031 /**
1032 * Throws {@link NoSuchMethodError}.
1033 *
1034 * @deprecated This method was originally designed to destroy this
1035 * thread without any cleanup. Any monitors it held would have
1036 * remained locked. However, the method was never implemented.
1037 * If it were to be implemented, it would be deadlock-prone in
1038 * much the manner of {@link #suspend}. If the target thread held
1039 * a lock protecting a critical system resource when it was
1040 * destroyed, no thread could ever access this resource again.
1041 * If another thread ever attempted to lock this resource, deadlock
1042 * would result. Such deadlocks typically manifest themselves as
1043 * "frozen" processes. For more information, see
1044 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">
1045 * Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1046 * @throws NoSuchMethodError always
1047 */
1048 @Deprecated
1049 public void destroy() {
1050 throw new NoSuchMethodError();
1051 }
1052
1053 /**
1054 * Tests if this thread is alive. A thread is alive if it has
1055 * been started and has not yet died.
1056 *
1057 * @return <code>true</code> if this thread is alive;
1058 * <code>false</code> otherwise.
1059 */
1060 public final native boolean isAlive();
1061
1062 /**
1063 * Suspends this thread.
1064 * <p>
1065 * First, the <code>checkAccess</code> method of this thread is called
1066 * with no arguments. This may result in throwing a
1067 * <code>SecurityException </code>(in the current thread).
1068 * <p>
1069 * If the thread is alive, it is suspended and makes no further
1070 * progress unless and until it is resumed.
1071 *
1072 * @exception SecurityException if the current thread cannot modify
1073 * this thread.
1074 * @see #checkAccess
1075 * @deprecated This method has been deprecated, as it is
1076 * inherently deadlock-prone. If the target thread holds a lock on the
1077 * monitor protecting a critical system resource when it is suspended, no
1078 * thread can access this resource until the target thread is resumed. If
1079 * the thread that would resume the target thread attempts to lock this
1080 * monitor prior to calling <code>resume</code>, deadlock results. Such
1081 * deadlocks typically manifest themselves as "frozen" processes.
1082 * For more information, see
1083 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
1084 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1085 */
1086 @Deprecated
1087 public final void suspend() {
1088 checkAccess();
1089 suspend0();
1090 }
1091
1092 /**
1093 * Resumes a suspended thread.
1094 * <p>
1095 * First, the <code>checkAccess</code> method of this thread is called
1096 * with no arguments. This may result in throwing a
1097 * <code>SecurityException</code> (in the current thread).
1098 * <p>
1099 * If the thread is alive but suspended, it is resumed and is
1100 * permitted to make progress in its execution.
1101 *
1102 * @exception SecurityException if the current thread cannot modify this
1103 * thread.
1104 * @see #checkAccess
1105 * @see #suspend()
1106 * @deprecated This method exists solely for use with {@link #suspend},
1107 * which has been deprecated because it is deadlock-prone.
1108 * For more information, see
1109 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
1110 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1111 */
1112 @Deprecated
1113 public final void resume() {
1114 checkAccess();
1115 resume0();
1116 }
1117
1118 /**
1119 * Changes the priority of this thread.
1120 * <p>
1121 * First the <code>checkAccess</code> method of this thread is called
1122 * with no arguments. This may result in throwing a
1123 * <code>SecurityException</code>.
1124 * <p>
1125 * Otherwise, the priority of this thread is set to the smaller of
1126 * the specified <code>newPriority</code> and the maximum permitted
1127 * priority of the thread's thread group.
1128 *
1129 * @param newPriority priority to set this thread to
1130 * @exception IllegalArgumentException If the priority is not in the
1131 * range <code>MIN_PRIORITY</code> to
1132 * <code>MAX_PRIORITY</code>.
1133 * @exception SecurityException if the current thread cannot modify
1134 * this thread.
1135 * @see #getPriority
1136 * @see #checkAccess()
1137 * @see #getThreadGroup()
1138 * @see #MAX_PRIORITY
1139 * @see #MIN_PRIORITY
1140 * @see ThreadGroup#getMaxPriority()
1141 */
1142 public final void setPriority(int newPriority) {
1143 ThreadGroup g;
1144 checkAccess();
1145 if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
1146 throw new IllegalArgumentException();
1147 }
1148 if((g = getThreadGroup()) != null) {
1149 if (newPriority > g.getMaxPriority()) {
1150 newPriority = g.getMaxPriority();
1151 }
1152 setPriority0(priority = newPriority);
1153 }
1154 }
1155
1156 /**
1157 * Returns this thread's priority.
1158 *
1159 * @return this thread's priority.
1160 * @see #setPriority
1161 */
1162 public final int getPriority() {
1163 return priority;
1164 }
1165
1166 /**
1167 * Changes the name of this thread to be equal to the argument
1168 * <code>name</code>.
1169 * <p>
1170 * First the <code>checkAccess</code> method of this thread is called
1171 * with no arguments. This may result in throwing a
1172 * <code>SecurityException</code>.
1173 *
1174 * @param name the new name for this thread.
1175 * @exception SecurityException if the current thread cannot modify this
1176 * thread.
1177 * @see #getName
1178 * @see #checkAccess()
1179 */
1180 public final synchronized void setName(String name) {
1181 checkAccess();
1182 if (name == null) {
1183 throw new NullPointerException("name cannot be null");
1184 }
1185
1186 this.name = name;
1187 if (threadStatus != 0) {
1188 setNativeName(name);
1189 }
1190 }
1191
1192 /**
1193 * Returns this thread's name.
1194 *
1195 * @return this thread's name.
1196 * @see #setName(String)
1197 */
1198 public final String getName() {
1199 return name;
1200 }
1201
1202 /**
1203 * Returns the thread group to which this thread belongs.
1204 * This method returns null if this thread has died
1205 * (been stopped).
1206 *
1207 * @return this thread's thread group.
1208 */
1209 public final ThreadGroup getThreadGroup() {
1210 return group;
1211 }
1212
1213 /**
1214 * Returns an estimate of the number of active threads in the current
1215 * thread's {@linkplain java.lang.ThreadGroup thread group} and its
1216 * subgroups. Recursively iterates over all subgroups in the current
1217 * thread's thread group.
1218 *
1219 * <p> The value returned is only an estimate because the number of
1220 * threads may change dynamically while this method traverses internal
1221 * data structures, and might be affected by the presence of certain
1222 * system threads. This method is intended primarily for debugging
1223 * and monitoring purposes.
1224 *
1225 * @return an estimate of the number of active threads in the current
1226 * thread's thread group and in any other thread group that
1227 * has the current thread's thread group as an ancestor
1228 */
1229 public static int activeCount() {
1230 return currentThread().getThreadGroup().activeCount();
1231 }
1232
1233 /**
1234 * Copies into the specified array every active thread in the current
1235 * thread's thread group and its subgroups. This method simply
1236 * invokes the {@link java.lang.ThreadGroup#enumerate(Thread[])}
1237 * method of the current thread's thread group.
1238 *
1239 * <p> An application might use the {@linkplain #activeCount activeCount}
1240 * method to get an estimate of how big the array should be, however
1241 * <i>if the array is too short to hold all the threads, the extra threads
1242 * are silently ignored.</i> If it is critical to obtain every active
1243 * thread in the current thread's thread group and its subgroups, the
1244 * invoker should verify that the returned int value is strictly less
1245 * than the length of {@code tarray}.
1246 *
1247 * <p> Due to the inherent race condition in this method, it is recommended
1248 * that the method only be used for debugging and monitoring purposes.
1249 *
1250 * @param tarray
1251 * an array into which to put the list of threads
1252 *
1253 * @return the number of threads put into the array
1254 *
1255 * @throws SecurityException
1256 * if {@link java.lang.ThreadGroup#checkAccess} determines that
1257 * the current thread cannot access its thread group
1258 */
1259 public static int enumerate(Thread tarray[]) {
1260 return currentThread().getThreadGroup().enumerate(tarray);
1261 }
1262
1263 /**
1264 * Counts the number of stack frames in this thread. The thread must
1265 * be suspended.
1266 *
1267 * @return the number of stack frames in this thread.
1268 * @exception IllegalThreadStateException if this thread is not
1269 * suspended.
1270 * @deprecated The definition of this call depends on {@link #suspend},
1271 * which is deprecated. Further, the results of this call
1272 * were never well-defined.
1273 */
1274 @Deprecated
1275 public native int countStackFrames();
1276
1277 /**
1278 * Waits at most {@code millis} milliseconds for this thread to
1279 * die. A timeout of {@code 0} means to wait forever.
1280 *
1281 * <p> This implementation uses a loop of {@code this.wait} calls
1282 * conditioned on {@code this.isAlive}. As a thread terminates the
1283 * {@code this.notifyAll} method is invoked. It is recommended that
1284 * applications not use {@code wait}, {@code notify}, or
1285 * {@code notifyAll} on {@code Thread} instances.
1286 *
1287 * @param millis
1288 * the time to wait in milliseconds
1289 *
1290 * @throws IllegalArgumentException
1291 * if the value of {@code millis} is negative
1292 *
1293 * @throws InterruptedException
1294 * if any thread has interrupted the current thread. The
1295 * <i>interrupted status</i> of the current thread is
1296 * cleared when this exception is thrown.
1297 */
1298 public final synchronized void join(long millis)
1299 throws InterruptedException {
1300 long base = System.currentTimeMillis();
1301 long now = 0;
1302
1303 if (millis < 0) {
1304 throw new IllegalArgumentException("timeout value is negative");
1305 }
1306
1307 if (millis == 0) {
1308 while (isAlive()) {
1309 wait(0);
1310 }
1311 } else {
1312 while (isAlive()) {
1313 long delay = millis - now;
1314 if (delay <= 0) {
1315 break;
1316 }
1317 wait(delay);
1318 now = System.currentTimeMillis() - base;
1319 }
1320 }
1321 }
1322
1323 /**
1324 * Waits at most {@code millis} milliseconds plus
1325 * {@code nanos} nanoseconds for this thread to die.
1326 *
1327 * <p> This implementation uses a loop of {@code this.wait} calls
1328 * conditioned on {@code this.isAlive}. As a thread terminates the
1329 * {@code this.notifyAll} method is invoked. It is recommended that
1330 * applications not use {@code wait}, {@code notify}, or
1331 * {@code notifyAll} on {@code Thread} instances.
1332 *
1333 * @param millis
1334 * the time to wait in milliseconds
1335 *
1336 * @param nanos
1337 * {@code 0-999999} additional nanoseconds to wait
1338 *
1339 * @throws IllegalArgumentException
1340 * if the value of {@code millis} is negative, or the value
1341 * of {@code nanos} is not in the range {@code 0-999999}
1342 *
1343 * @throws InterruptedException
1344 * if any thread has interrupted the current thread. The
1345 * <i>interrupted status</i> of the current thread is
1346 * cleared when this exception is thrown.
1347 */
1348 public final synchronized void join(long millis, int nanos)
1349 throws InterruptedException {
1350
1351 if (millis < 0) {
1352 throw new IllegalArgumentException("timeout value is negative");
1353 }
1354
1355 if (nanos < 0 || nanos > 999999) {
1356 throw new IllegalArgumentException(
1357 "nanosecond timeout value out of range");
1358 }
1359
1360 if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
1361 millis++;
1362 }
1363
1364 join(millis);
1365 }
1366
1367 /**
1368 * Waits for this thread to die.
1369 *
1370 * <p> An invocation of this method behaves in exactly the same
1371 * way as the invocation
1372 *
1373 * <blockquote>
1374 * {@linkplain #join(long) join}{@code (0)}
1375 * </blockquote>
1376 *
1377 * @throws InterruptedException
1378 * if any thread has interrupted the current thread. The
1379 * <i>interrupted status</i> of the current thread is
1380 * cleared when this exception is thrown.
1381 */
1382 public final void join() throws InterruptedException {
1383 join(0);
1384 }
1385
1386 /**
1387 * Prints a stack trace of the current thread to the standard error stream.
1388 * This method is used only for debugging.
1389 */
1390 public static void dumpStack() {
1391 StackStreamFactory.makeStackTrace().printStackTrace(System.err);
1392 }
1393
1394 /**
1395 * Marks this thread as either a {@linkplain #isDaemon daemon} thread
1396 * or a user thread. The Java Virtual Machine exits when the only
1397 * threads running are all daemon threads.
1398 *
1399 * <p> This method must be invoked before the thread is started.
1400 *
1401 * @param on
1402 * if {@code true}, marks this thread as a daemon thread
1403 *
1404 * @throws IllegalThreadStateException
1405 * if this thread is {@linkplain #isAlive alive}
1406 *
1407 * @throws SecurityException
1408 * if {@link #checkAccess} determines that the current
1409 * thread cannot modify this thread
1410 */
1411 public final void setDaemon(boolean on) {
1412 checkAccess();
1413 if (isAlive()) {
1414 throw new IllegalThreadStateException();
1415 }
1416 daemon = on;
1417 }
1418
1419 /**
1420 * Tests if this thread is a daemon thread.
1421 *
1422 * @return <code>true</code> if this thread is a daemon thread;
1423 * <code>false</code> otherwise.
1424 * @see #setDaemon(boolean)
1425 */
1426 public final boolean isDaemon() {
1427 return daemon;
1428 }
1429
1430 /**
1431 * Determines if the currently running thread has permission to
1432 * modify this thread.
1433 * <p>
1434 * If there is a security manager, its <code>checkAccess</code> method
1435 * is called with this thread as its argument. This may result in
1436 * throwing a <code>SecurityException</code>.
1437 *
1438 * @exception SecurityException if the current thread is not allowed to
1439 * access this thread.
1440 * @see SecurityManager#checkAccess(Thread)
1441 */
1442 public final void checkAccess() {
1443 SecurityManager security = System.getSecurityManager();
1444 if (security != null) {
1445 security.checkAccess(this);
1446 }
1447 }
1448
1449 /**
1450 * Returns a string representation of this thread, including the
1451 * thread's name, priority, and thread group.
1452 *
1453 * @return a string representation of this thread.
1454 */
1455 public String toString() {
1456 ThreadGroup group = getThreadGroup();
1457 if (group != null) {
1458 return "Thread[" + getName() + "," + getPriority() + "," +
1459 group.getName() + "]";
1460 } else {
1461 return "Thread[" + getName() + "," + getPriority() + "," +
1462 "" + "]";
1463 }
1464 }
1465
1466 /**
1467 * Returns the context ClassLoader for this Thread. The context
1468 * ClassLoader is provided by the creator of the thread for use
1469 * by code running in this thread when loading classes and resources.
1470 * If not {@linkplain #setContextClassLoader set}, the default is the
1471 * ClassLoader context of the parent Thread. The context ClassLoader of the
1472 * primordial thread is typically set to the class loader used to load the
1473 * application.
1474 *
1475 * <p>If a security manager is present, and the invoker's class loader is not
1476 * {@code null} and is not the same as or an ancestor of the context class
1477 * loader, then this method invokes the security manager's {@link
1478 * SecurityManager#checkPermission(java.security.Permission) checkPermission}
1479 * method with a {@link RuntimePermission RuntimePermission}{@code
1480 * ("getClassLoader")} permission to verify that retrieval of the context
1481 * class loader is permitted.
1482 *
1483 * @return the context ClassLoader for this Thread, or {@code null}
1484 * indicating the system class loader (or, failing that, the
1485 * bootstrap class loader)
1486 *
1487 * @throws SecurityException
1488 * if the current thread cannot get the context ClassLoader
1489 *
1490 * @since 1.2
1491 */
1492 @CallerSensitive
1493 public ClassLoader getContextClassLoader() {
1494 if (contextClassLoader == null)
1495 return null;
1496 SecurityManager sm = System.getSecurityManager();
1497 if (sm != null) {
1498 ClassLoader.checkClassLoaderPermission(contextClassLoader,
1499 Reflection.getCallerClass());
1500 }
1501 return contextClassLoader;
1502 }
1503
1504 /**
1505 * Sets the context ClassLoader for this Thread. The context
1506 * ClassLoader can be set when a thread is created, and allows
1507 * the creator of the thread to provide the appropriate class loader,
1508 * through {@code getContextClassLoader}, to code running in the thread
1509 * when loading classes and resources.
1510 *
1511 * <p>If a security manager is present, its {@link
1512 * SecurityManager#checkPermission(java.security.Permission) checkPermission}
1513 * method is invoked with a {@link RuntimePermission RuntimePermission}{@code
1514 * ("setContextClassLoader")} permission to see if setting the context
1515 * ClassLoader is permitted.
1516 *
1517 * @param cl
1518 * the context ClassLoader for this Thread, or null indicating the
1519 * system class loader (or, failing that, the bootstrap class loader)
1520 *
1521 * @throws SecurityException
1522 * if the current thread cannot set the context ClassLoader
1523 *
1524 * @since 1.2
1525 */
1526 public void setContextClassLoader(ClassLoader cl) {
1527 SecurityManager sm = System.getSecurityManager();
1528 if (sm != null) {
1529 sm.checkPermission(new RuntimePermission("setContextClassLoader"));
1530 }
1531 contextClassLoader = cl;
1532 }
1533
1534 /**
1535 * Returns {@code true} if and only if the current thread holds the
1536 * monitor lock on the specified object.
1537 *
1538 * <p>This method is designed to allow a program to assert that
1539 * the current thread already holds a specified lock:
1540 * <pre>
1541 * assert Thread.holdsLock(obj);
1542 * </pre>
1543 *
1544 * @param obj the object on which to test lock ownership
1545 * @throws NullPointerException if obj is {@code null}
1546 * @return {@code true} if the current thread holds the monitor lock on
1547 * the specified object.
1548 * @since 1.4
1549 */
1550 public static native boolean holdsLock(Object obj);
1551
1552 private static final StackTraceElement[] EMPTY_STACK_TRACE
1553 = new StackTraceElement[0];
1554
1555 /**
1556 * Returns an array of stack trace elements representing the stack dump
1557 * of this thread. This method will return a zero-length array if
1558 * this thread has not started, has started but has not yet been
1559 * scheduled to run by the system, or has terminated.
1560 * If the returned array is of non-zero length then the first element of
1561 * the array represents the top of the stack, which is the most recent
1562 * method invocation in the sequence. The last element of the array
1563 * represents the bottom of the stack, which is the least recent method
1564 * invocation in the sequence.
1565 *
1566 * <p>If there is a security manager, and this thread is not
1567 * the current thread, then the security manager's
1568 * {@code checkPermission} method is called with a
1569 * {@code RuntimePermission("getStackTrace")} permission
1570 * to see if it's ok to get the stack trace.
1571 *
1572 * <p>Some virtual machines may, under some circumstances, omit one
1573 * or more stack frames from the stack trace. In the extreme case,
1574 * a virtual machine that has no stack trace information concerning
1575 * this thread is permitted to return a zero-length array from this
1576 * method.
1577 *
1578 * @return an array of {@code StackTraceElement},
1579 * each represents one stack frame.
1580 *
1581 * @throws SecurityException
1582 * if a security manager exists and its
1583 * {@code checkPermission} method doesn't allow
1584 * getting the stack trace of thread.
1585 * @see SecurityManager#checkPermission
1586 * @see RuntimePermission
1587 * @see Throwable#getStackTrace
1588 *
1589 * @since 1.5
1590 */
1591 public StackTraceElement[] getStackTrace() {
1592 if (this != Thread.currentThread()) {
1593 // check for getStackTrace permission
1594 SecurityManager security = System.getSecurityManager();
1595 if (security != null) {
1596 security.checkPermission(
1597 SecurityConstants.GET_STACK_TRACE_PERMISSION);
1598 }
1599 // optimization so we do not call into the vm for threads that
1600 // have not yet started or have terminated
1601 if (!isAlive()) {
1602 return EMPTY_STACK_TRACE;
1603 }
1604 StackTraceElement[][] stackTraceArray = dumpThreads(new Thread[] {this});
1605 StackTraceElement[] stackTrace = stackTraceArray[0];
1606 // a thread that was alive during the previous isAlive call may have
1607 // since terminated, therefore not having a stacktrace.
1608 if (stackTrace == null) {
1609 stackTrace = EMPTY_STACK_TRACE;
1610 }
1611 return stackTrace;
1612 } else {
1613 // Don't need JVM help for current thread
1614 return StackStreamFactory.makeStackTrace().getStackTraceElements();
1615 }
1616 }
1617
1618 /**
1619 * Returns a map of stack traces for all live threads.
1620 * The map keys are threads and each map value is an array of
1621 * {@code StackTraceElement} that represents the stack dump
1622 * of the corresponding {@code Thread}.
1623 * The returned stack traces are in the format specified for
1624 * the {@link #getStackTrace getStackTrace} method.
1625 *
1626 * <p>The threads may be executing while this method is called.
1627 * The stack trace of each thread only represents a snapshot and
1628 * each stack trace may be obtained at different time. A zero-length
1629 * array will be returned in the map value if the virtual machine has
1630 * no stack trace information about a thread.
1631 *
1632 * <p>If there is a security manager, then the security manager's
1633 * {@code checkPermission} method is called with a
1634 * {@code RuntimePermission("getStackTrace")} permission as well as
1635 * {@code RuntimePermission("modifyThreadGroup")} permission
1636 * to see if it is ok to get the stack trace of all threads.
1637 *
1638 * @return a {@code Map} from {@code Thread} to an array of
1639 * {@code StackTraceElement} that represents the stack trace of
1640 * the corresponding thread.
1641 *
1642 * @throws SecurityException
1643 * if a security manager exists and its
1644 * {@code checkPermission} method doesn't allow
1645 * getting the stack trace of thread.
1646 * @see #getStackTrace
1647 * @see SecurityManager#checkPermission
1648 * @see RuntimePermission
1649 * @see Throwable#getStackTrace
1650 *
1651 * @since 1.5
1652 */
1653 public static Map<Thread, StackTraceElement[]> getAllStackTraces() {
1654 // check for getStackTrace permission
1655 SecurityManager security = System.getSecurityManager();
1656 if (security != null) {
1657 security.checkPermission(
1658 SecurityConstants.GET_STACK_TRACE_PERMISSION);
1659 security.checkPermission(
1660 SecurityConstants.MODIFY_THREADGROUP_PERMISSION);
1661 }
1662
1663 // Get a snapshot of the list of all threads
1664 Thread[] threads = getThreads();
1665 StackTraceElement[][] traces = dumpThreads(threads);
1666 Map<Thread, StackTraceElement[]> m = new HashMap<>(threads.length);
1667 for (int i = 0; i < threads.length; i++) {
1668 StackTraceElement[] stackTrace = traces[i];
1669 if (stackTrace != null) {
1670 m.put(threads[i], stackTrace);
1671 }
1672 // else terminated so we don't put it in the map
1673 }
1674 return m;
1675 }
1676
1677
1678 private static final RuntimePermission SUBCLASS_IMPLEMENTATION_PERMISSION =
1679 new RuntimePermission("enableContextClassLoaderOverride");
1680
1681 /** cache of subclass security audit results */
1682 /* Replace with ConcurrentReferenceHashMap when/if it appears in a future
1683 * release */
1684 private static class Caches {
1685 /** cache of subclass security audit results */
1686 static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits =
1687 new ConcurrentHashMap<>();
1688
1689 /** queue for WeakReferences to audited subclasses */
1690 static final ReferenceQueue<Class<?>> subclassAuditsQueue =
1691 new ReferenceQueue<>();
1692 }
1693
1694 /**
1695 * Verifies that this (possibly subclass) instance can be constructed
1696 * without violating security constraints: the subclass must not override
1697 * security-sensitive non-final methods, or else the
1698 * "enableContextClassLoaderOverride" RuntimePermission is checked.
1699 */
1700 private static boolean isCCLOverridden(Class<?> cl) {
1701 if (cl == Thread.class)
1702 return false;
1703
1704 processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits);
1705 WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue);
1706 Boolean result = Caches.subclassAudits.get(key);
1707 if (result == null) {
1708 result = Boolean.valueOf(auditSubclass(cl));
1709 Caches.subclassAudits.putIfAbsent(key, result);
1710 }
1711
1712 return result.booleanValue();
1713 }
1714
1715 /**
1716 * Performs reflective checks on given subclass to verify that it doesn't
1717 * override security-sensitive non-final methods. Returns true if the
1718 * subclass overrides any of the methods, false otherwise.
1719 */
1720 private static boolean auditSubclass(final Class<?> subcl) {
1721 Boolean result = AccessController.doPrivileged(
1722 new PrivilegedAction<>() {
1723 public Boolean run() {
1724 for (Class<?> cl = subcl;
1725 cl != Thread.class;
1726 cl = cl.getSuperclass())
1727 {
1728 try {
1729 cl.getDeclaredMethod("getContextClassLoader", new Class<?>[0]);
1730 return Boolean.TRUE;
1731 } catch (NoSuchMethodException ex) {
1732 }
1733 try {
1734 Class<?>[] params = {ClassLoader.class};
1735 cl.getDeclaredMethod("setContextClassLoader", params);
1736 return Boolean.TRUE;
1737 } catch (NoSuchMethodException ex) {
1738 }
1739 }
1740 return Boolean.FALSE;
1741 }
1742 }
1743 );
1744 return result.booleanValue();
1745 }
1746
1747 private static native StackTraceElement[][] dumpThreads(Thread[] threads);
1748 private static native Thread[] getThreads();
1749
1750 /**
1751 * Returns the identifier of this Thread. The thread ID is a positive
1752 * {@code long} number generated when this thread was created.
1753 * The thread ID is unique and remains unchanged during its lifetime.
1754 * When a thread is terminated, this thread ID may be reused.
1755 *
1756 * @return this thread's ID.
1757 * @since 1.5
1758 */
1759 public long getId() {
1760 return tid;
1761 }
1762
1763 /**
1764 * A thread state. A thread can be in one of the following states:
1765 * <ul>
1766 * <li>{@link #NEW}<br>
1767 * A thread that has not yet started is in this state.
1768 * </li>
1769 * <li>{@link #RUNNABLE}<br>
1770 * A thread executing in the Java virtual machine is in this state.
1771 * </li>
1772 * <li>{@link #BLOCKED}<br>
1773 * A thread that is blocked waiting for a monitor lock
1774 * is in this state.
1775 * </li>
1776 * <li>{@link #WAITING}<br>
1777 * A thread that is waiting indefinitely for another thread to
1778 * perform a particular action is in this state.
1779 * </li>
1780 * <li>{@link #TIMED_WAITING}<br>
1781 * A thread that is waiting for another thread to perform an action
1782 * for up to a specified waiting time is in this state.
1783 * </li>
1784 * <li>{@link #TERMINATED}<br>
1785 * A thread that has exited is in this state.
1786 * </li>
1787 * </ul>
1788 *
1789 * <p>
1790 * A thread can be in only one state at a given point in time.
1791 * These states are virtual machine states which do not reflect
1792 * any operating system thread states.
1793 *
1794 * @since 1.5
1795 * @see #getState
1796 */
1797 public enum State {
1798 /**
1799 * Thread state for a thread which has not yet started.
1800 */
1801 NEW,
1802
1803 /**
1804 * Thread state for a runnable thread. A thread in the runnable
1805 * state is executing in the Java virtual machine but it may
1806 * be waiting for other resources from the operating system
1807 * such as processor.
1808 */
1809 RUNNABLE,
1810
1811 /**
1812 * Thread state for a thread blocked waiting for a monitor lock.
1813 * A thread in the blocked state is waiting for a monitor lock
1814 * to enter a synchronized block/method or
1815 * reenter a synchronized block/method after calling
1816 * {@link Object#wait() Object.wait}.
1817 */
1818 BLOCKED,
1819
1820 /**
1821 * Thread state for a waiting thread.
1822 * A thread is in the waiting state due to calling one of the
1823 * following methods:
1824 * <ul>
1825 * <li>{@link Object#wait() Object.wait} with no timeout</li>
1826 * <li>{@link #join() Thread.join} with no timeout</li>
1827 * <li>{@link LockSupport#park() LockSupport.park}</li>
1828 * </ul>
1829 *
1830 * <p>A thread in the waiting state is waiting for another thread to
1831 * perform a particular action.
1832 *
1833 * For example, a thread that has called {@code Object.wait()}
1834 * on an object is waiting for another thread to call
1835 * {@code Object.notify()} or {@code Object.notifyAll()} on
1836 * that object. A thread that has called {@code Thread.join()}
1837 * is waiting for a specified thread to terminate.
1838 */
1839 WAITING,
1840
1841 /**
1842 * Thread state for a waiting thread with a specified waiting time.
1843 * A thread is in the timed waiting state due to calling one of
1844 * the following methods with a specified positive waiting time:
1845 * <ul>
1846 * <li>{@link #sleep Thread.sleep}</li>
1847 * <li>{@link Object#wait(long) Object.wait} with timeout</li>
1848 * <li>{@link #join(long) Thread.join} with timeout</li>
1849 * <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
1850 * <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
1851 * </ul>
1852 */
1853 TIMED_WAITING,
1854
1855 /**
1856 * Thread state for a terminated thread.
1857 * The thread has completed execution.
1858 */
1859 TERMINATED;
1860 }
1861
1862 /**
1863 * Returns the state of this thread.
1864 * This method is designed for use in monitoring of the system state,
1865 * not for synchronization control.
1866 *
1867 * @return this thread's state.
1868 * @since 1.5
1869 */
1870 public State getState() {
1871 // get current thread state
1872 return jdk.internal.misc.VM.toThreadState(threadStatus);
1873 }
1874
1875 // Added in JSR-166
1876
1877 /**
1878 * Interface for handlers invoked when a {@code Thread} abruptly
1879 * terminates due to an uncaught exception.
1880 * <p>When a thread is about to terminate due to an uncaught exception
1881 * the Java Virtual Machine will query the thread for its
1882 * {@code UncaughtExceptionHandler} using
1883 * {@link #getUncaughtExceptionHandler} and will invoke the handler's
1884 * {@code uncaughtException} method, passing the thread and the
1885 * exception as arguments.
1886 * If a thread has not had its {@code UncaughtExceptionHandler}
1887 * explicitly set, then its {@code ThreadGroup} object acts as its
1888 * {@code UncaughtExceptionHandler}. If the {@code ThreadGroup} object
1889 * has no
1890 * special requirements for dealing with the exception, it can forward
1891 * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler
1892 * default uncaught exception handler}.
1893 *
1894 * @see #setDefaultUncaughtExceptionHandler
1895 * @see #setUncaughtExceptionHandler
1896 * @see ThreadGroup#uncaughtException
1897 * @since 1.5
1898 */
1899 @FunctionalInterface
1900 public interface UncaughtExceptionHandler {
1901 /**
1902 * Method invoked when the given thread terminates due to the
1903 * given uncaught exception.
1904 * <p>Any exception thrown by this method will be ignored by the
1905 * Java Virtual Machine.
1906 * @param t the thread
1907 * @param e the exception
1908 */
1909 void uncaughtException(Thread t, Throwable e);
1910 }
1911
1912 // null unless explicitly set
1913 private volatile UncaughtExceptionHandler uncaughtExceptionHandler;
1914
1915 // null unless explicitly set
1916 private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler;
1917
1918 /**
1919 * Set the default handler invoked when a thread abruptly terminates
1920 * due to an uncaught exception, and no other handler has been defined
1921 * for that thread.
1922 *
1923 * <p>Uncaught exception handling is controlled first by the thread, then
1924 * by the thread's {@link ThreadGroup} object and finally by the default
1925 * uncaught exception handler. If the thread does not have an explicit
1926 * uncaught exception handler set, and the thread's thread group
1927 * (including parent thread groups) does not specialize its
1928 * {@code uncaughtException} method, then the default handler's
1929 * {@code uncaughtException} method will be invoked.
1930 * <p>By setting the default uncaught exception handler, an application
1931 * can change the way in which uncaught exceptions are handled (such as
1932 * logging to a specific device, or file) for those threads that would
1933 * already accept whatever "default" behavior the system
1934 * provided.
1935 *
1936 * <p>Note that the default uncaught exception handler should not usually
1937 * defer to the thread's {@code ThreadGroup} object, as that could cause
1938 * infinite recursion.
1939 *
1940 * @param eh the object to use as the default uncaught exception handler.
1941 * If {@code null} then there is no default handler.
1942 *
1943 * @throws SecurityException if a security manager is present and it denies
1944 * {@link RuntimePermission}{@code ("setDefaultUncaughtExceptionHandler")}
1945 *
1946 * @see #setUncaughtExceptionHandler
1947 * @see #getUncaughtExceptionHandler
1948 * @see ThreadGroup#uncaughtException
1949 * @since 1.5
1950 */
1951 public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
1952 SecurityManager sm = System.getSecurityManager();
1953 if (sm != null) {
1954 sm.checkPermission(
1955 new RuntimePermission("setDefaultUncaughtExceptionHandler")
1956 );
1957 }
1958
1959 defaultUncaughtExceptionHandler = eh;
1960 }
1961
1962 /**
1963 * Returns the default handler invoked when a thread abruptly terminates
1964 * due to an uncaught exception. If the returned value is {@code null},
1965 * there is no default.
1966 * @since 1.5
1967 * @see #setDefaultUncaughtExceptionHandler
1968 * @return the default uncaught exception handler for all threads
1969 */
1970 public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler(){
1971 return defaultUncaughtExceptionHandler;
1972 }
1973
1974 /**
1975 * Returns the handler invoked when this thread abruptly terminates
1976 * due to an uncaught exception. If this thread has not had an
1977 * uncaught exception handler explicitly set then this thread's
1978 * {@code ThreadGroup} object is returned, unless this thread
1979 * has terminated, in which case {@code null} is returned.
1980 * @since 1.5
1981 * @return the uncaught exception handler for this thread
1982 */
1983 public UncaughtExceptionHandler getUncaughtExceptionHandler() {
1984 return uncaughtExceptionHandler != null ?
1985 uncaughtExceptionHandler : group;
1986 }
1987
1988 /**
1989 * Set the handler invoked when this thread abruptly terminates
1990 * due to an uncaught exception.
1991 * <p>A thread can take full control of how it responds to uncaught
1992 * exceptions by having its uncaught exception handler explicitly set.
1993 * If no such handler is set then the thread's {@code ThreadGroup}
1994 * object acts as its handler.
1995 * @param eh the object to use as this thread's uncaught exception
1996 * handler. If {@code null} then this thread has no explicit handler.
1997 * @throws SecurityException if the current thread is not allowed to
1998 * modify this thread.
1999 * @see #setDefaultUncaughtExceptionHandler
2000 * @see ThreadGroup#uncaughtException
2001 * @since 1.5
2002 */
2003 public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
2004 checkAccess();
2005 uncaughtExceptionHandler = eh;
2006 }
2007
2008 /**
2009 * Dispatch an uncaught exception to the handler. This method is
2010 * intended to be called only by the JVM.
2011 */
2012 private void dispatchUncaughtException(Throwable e) {
2013 getUncaughtExceptionHandler().uncaughtException(this, e);
2014 }
2015
2016 /**
2017 * Removes from the specified map any keys that have been enqueued
2018 * on the specified reference queue.
2019 */
2020 static void processQueue(ReferenceQueue<Class<?>> queue,
2021 ConcurrentMap<? extends
2022 WeakReference<Class<?>>, ?> map)
2023 {
2024 Reference<? extends Class<?>> ref;
2025 while((ref = queue.poll()) != null) {
2026 map.remove(ref);
2027 }
2028 }
2029
2030 /**
2031 * Weak key for Class objects.
2032 **/
2033 static class WeakClassKey extends WeakReference<Class<?>> {
2034 /**
2035 * saved value of the referent's identity hash code, to maintain
2036 * a consistent hash code after the referent has been cleared
2037 */
2038 private final int hash;
2039
2040 /**
2041 * Create a new WeakClassKey to the given object, registered
2042 * with a queue.
2043 */
2044 WeakClassKey(Class<?> cl, ReferenceQueue<Class<?>> refQueue) {
2045 super(cl, refQueue);
2046 hash = System.identityHashCode(cl);
2047 }
2048
2049 /**
2050 * Returns the identity hash code of the original referent.
2051 */
2052 @Override
2053 public int hashCode() {
2054 return hash;
2055 }
2056
2057 /**
2058 * Returns true if the given object is this identical
2059 * WeakClassKey instance, or, if this object's referent has not
2060 * been cleared, if the given object is another WeakClassKey
2061 * instance with the identical non-null referent as this one.
2062 */
2063 @Override
2064 public boolean equals(Object obj) {
2065 if (obj == this)
2066 return true;
2067
2068 if (obj instanceof WeakClassKey) {
2069 Object referent = get();
2070 return (referent != null) &&
2071 (referent == ((WeakClassKey) obj).get());
2072 } else {
2073 return false;
2074 }
2075 }
2076 }
2077
2078
2079 // The following three initially uninitialized fields are exclusively
2080 // managed by class java.util.concurrent.ThreadLocalRandom. These
2081 // fields are used to build the high-performance PRNGs in the
2082 // concurrent code, and we can not risk accidental false sharing.
2083 // Hence, the fields are isolated with @Contended.
2084
2085 /** The current seed for a ThreadLocalRandom */
2086 @jdk.internal.vm.annotation.Contended("tlr")
2087 long threadLocalRandomSeed;
2088
2089 /** Probe hash value; nonzero if threadLocalRandomSeed initialized */
2090 @jdk.internal.vm.annotation.Contended("tlr")
2091 int threadLocalRandomProbe;
2092
2093 /** Secondary seed isolated from public ThreadLocalRandom sequence */
2094 @jdk.internal.vm.annotation.Contended("tlr")
2095 int threadLocalRandomSecondarySeed;
2096
2097 /* Some private helper methods */
2098 private native void setPriority0(int newPriority);
2099 private native void stop0(Object o);
2100 private native void suspend0();
2101 private native void resume0();
2102 private native void interrupt0();
2103 private native void setNativeName(String name);
2104 }