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 jdk.internal.reflect.CallerSensitive;
41 import jdk.internal.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 * Indicates that the caller is momentarily unable to progress, until the
345 * occurrence of one or more actions on the part of other activities. By
346 * invoking this method within each iteration of a spin-wait loop construct,
347 * the calling thread indicates to the runtime that it is busy-waiting.
348 * The runtime may take action to improve the performance of invoking
349 * spin-wait loop constructions.
350 * <p>
351 * @apiNote
352 * As an example consider a method in a class that spins in a loop until
353 * some flag is set outside of that method. A call to the {@code onSpinWait}
354 * method should be placed inside the spin loop.
355 * <pre>{@code
356 * class EventHandler {
357 * volatile boolean eventNotificationNotReceived;
358 * void waitForEventAndHandleIt() {
359 * while ( eventNotificationNotReceived ) {
360 * java.lang.Thread.onSpinWait();
361 * }
362 * readAndProcessEvent();
363 * }
364 *
365 * void readAndProcessEvent() {
366 * // Read event from some source and process it
367 * . . .
368 * }
369 * }
370 * }</pre>
371 * <p>
372 * The code above would remain correct even if the {@code onSpinWait}
373 * method was not called at all. However on some architectures the Java
374 * Virtual Machine may issue the processor instructions to address such
375 * code patterns in a more beneficial way.
376 * <p>
377 * @since 9
378 */
379 @HotSpotIntrinsicCandidate
380 public static void onSpinWait() {}
381
382 /**
383 * Initializes a Thread with the current AccessControlContext.
384 * @see #init(ThreadGroup,Runnable,String,long,AccessControlContext,boolean)
385 */
386 private void init(ThreadGroup g, Runnable target, String name,
387 long stackSize) {
388 init(g, target, name, stackSize, null, true);
389 }
390
391 /**
392 * Initializes a Thread.
393 *
394 * @param g the Thread group
395 * @param target the object whose run() method gets called
396 * @param name the name of the new Thread
397 * @param stackSize the desired stack size for the new thread, or
398 * zero to indicate that this parameter is to be ignored.
399 * @param acc the AccessControlContext to inherit, or
400 * AccessController.getContext() if null
401 * @param inheritThreadLocals if {@code true}, inherit initial values for
402 * inheritable thread-locals from the constructing thread
403 */
404 private void init(ThreadGroup g, Runnable target, String name,
405 long stackSize, AccessControlContext acc,
406 boolean inheritThreadLocals) {
407 if (name == null) {
408 throw new NullPointerException("name cannot be null");
409 }
410
411 this.name = name;
412
413 Thread parent = currentThread();
414 SecurityManager security = System.getSecurityManager();
415 if (g == null) {
416 /* Determine if it's an applet or not */
417
418 /* If there is a security manager, ask the security manager
419 what to do. */
420 if (security != null) {
421 g = security.getThreadGroup();
422 }
423
424 /* If the security doesn't have a strong opinion of the matter
425 use the parent thread group. */
426 if (g == null) {
427 g = parent.getThreadGroup();
428 }
429 }
430
431 /* checkAccess regardless of whether or not threadgroup is
432 explicitly passed in. */
433 g.checkAccess();
434
435 /*
436 * Do we have the required permissions?
437 */
438 if (security != null) {
439 if (isCCLOverridden(getClass())) {
440 security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
441 }
442 }
443
444 g.addUnstarted();
445
446 this.group = g;
447 this.daemon = parent.isDaemon();
448 this.priority = parent.getPriority();
449 if (security == null || isCCLOverridden(parent.getClass()))
450 this.contextClassLoader = parent.getContextClassLoader();
451 else
452 this.contextClassLoader = parent.contextClassLoader;
453 this.inheritedAccessControlContext =
454 acc != null ? acc : AccessController.getContext();
455 this.target = target;
456 setPriority(priority);
457 if (inheritThreadLocals && parent.inheritableThreadLocals != null)
458 this.inheritableThreadLocals =
459 ThreadLocal.createInheritedMap(parent.inheritableThreadLocals);
460 /* Stash the specified stack size in case the VM cares */
461 this.stackSize = stackSize;
462
463 /* Set thread ID */
464 tid = nextThreadID();
465 }
466
467 /**
468 * Throws CloneNotSupportedException as a Thread can not be meaningfully
469 * cloned. Construct a new Thread instead.
470 *
471 * @throws CloneNotSupportedException
472 * always
473 */
474 @Override
475 protected Object clone() throws CloneNotSupportedException {
476 throw new CloneNotSupportedException();
477 }
478
479 /**
480 * Allocates a new {@code Thread} object. This constructor has the same
481 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
482 * {@code (null, null, gname)}, where {@code gname} is a newly generated
483 * name. Automatically generated names are of the form
484 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
485 */
486 public Thread() {
487 init(null, null, "Thread-" + nextThreadNum(), 0);
488 }
489
490 /**
491 * Allocates a new {@code Thread} object. This constructor has the same
492 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
493 * {@code (null, target, gname)}, where {@code gname} is a newly generated
494 * name. Automatically generated names are of the form
495 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
496 *
497 * @param target
498 * the object whose {@code run} method is invoked when this thread
499 * is started. If {@code null}, this classes {@code run} method does
500 * nothing.
501 */
502 public Thread(Runnable target) {
503 init(null, target, "Thread-" + nextThreadNum(), 0);
504 }
505
506 /**
507 * Creates a new Thread that inherits the given AccessControlContext.
508 * This is not a public constructor.
509 */
510 Thread(Runnable target, AccessControlContext acc) {
511 init(null, target, "Thread-" + nextThreadNum(), 0, acc, true);
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, target, gname)} ,where {@code gname} is a newly generated
518 * name. Automatically generated names are of the form
519 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
520 *
521 * @param group
522 * the thread group. If {@code null} and there is a security
523 * manager, the group is determined by {@linkplain
524 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
525 * If there is not a security manager or {@code
526 * SecurityManager.getThreadGroup()} returns {@code null}, the group
527 * is set to the current thread's thread group.
528 *
529 * @param target
530 * the object whose {@code run} method is invoked when this thread
531 * is started. If {@code null}, this thread's run method is invoked.
532 *
533 * @throws SecurityException
534 * if the current thread cannot create a thread in the specified
535 * thread group
536 */
537 public Thread(ThreadGroup group, Runnable target) {
538 init(group, target, "Thread-" + nextThreadNum(), 0);
539 }
540
541 /**
542 * Allocates a new {@code Thread} object. This constructor has the same
543 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
544 * {@code (null, null, name)}.
545 *
546 * @param name
547 * the name of the new thread
548 */
549 public Thread(String name) {
550 init(null, null, name, 0);
551 }
552
553 /**
554 * Allocates a new {@code Thread} object. This constructor has the same
555 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
556 * {@code (group, null, name)}.
557 *
558 * @param group
559 * the thread group. If {@code null} and there is a security
560 * manager, the group is determined by {@linkplain
561 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
562 * If there is not a security manager or {@code
563 * SecurityManager.getThreadGroup()} returns {@code null}, the group
564 * is set to the current thread's thread group.
565 *
566 * @param name
567 * the name of the new thread
568 *
569 * @throws SecurityException
570 * if the current thread cannot create a thread in the specified
571 * thread group
572 */
573 public Thread(ThreadGroup group, String name) {
574 init(group, null, name, 0);
575 }
576
577 /**
578 * Allocates a new {@code Thread} object. This constructor has the same
579 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
580 * {@code (null, target, name)}.
581 *
582 * @param target
583 * the object whose {@code run} method is invoked when this thread
584 * is started. If {@code null}, this thread's run method is invoked.
585 *
586 * @param name
587 * the name of the new thread
588 */
589 public Thread(Runnable target, String name) {
590 init(null, target, name, 0);
591 }
592
593 /**
594 * Allocates a new {@code Thread} object so that it has {@code target}
595 * as its run object, has the specified {@code name} as its name,
596 * and belongs to the thread group referred to by {@code group}.
597 *
598 * <p>If there is a security manager, its
599 * {@link SecurityManager#checkAccess(ThreadGroup) checkAccess}
600 * method is invoked with the ThreadGroup as its argument.
601 *
602 * <p>In addition, its {@code checkPermission} method is invoked with
603 * the {@code RuntimePermission("enableContextClassLoaderOverride")}
604 * permission when invoked directly or indirectly by the constructor
605 * of a subclass which overrides the {@code getContextClassLoader}
606 * or {@code setContextClassLoader} methods.
607 *
608 * <p>The priority of the newly created thread is set equal to the
609 * priority of the thread creating it, that is, the currently running
610 * thread. The method {@linkplain #setPriority setPriority} may be
611 * used to change the priority to a new value.
612 *
613 * <p>The newly created thread is initially marked as being a daemon
614 * thread if and only if the thread creating it is currently marked
615 * as a daemon thread. The method {@linkplain #setDaemon setDaemon}
616 * may be used to change whether or not a thread is a daemon.
617 *
618 * @param group
619 * the thread group. If {@code null} and there is a security
620 * manager, the group is determined by {@linkplain
621 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
622 * If there is not a security manager or {@code
623 * SecurityManager.getThreadGroup()} returns {@code null}, the group
624 * is set to the current thread's thread group.
625 *
626 * @param target
627 * the object whose {@code run} method is invoked when this thread
628 * is started. If {@code null}, this thread's run method is invoked.
629 *
630 * @param name
631 * the name of the new thread
632 *
633 * @throws SecurityException
634 * if the current thread cannot create a thread in the specified
635 * thread group or cannot override the context class loader methods.
636 */
637 public Thread(ThreadGroup group, Runnable target, String name) {
638 init(group, target, name, 0);
639 }
640
641 /**
642 * Allocates a new {@code Thread} object so that it has {@code target}
643 * as its run object, has the specified {@code name} as its name,
644 * and belongs to the thread group referred to by {@code group}, and has
645 * the specified <i>stack size</i>.
646 *
647 * <p>This constructor is identical to {@link
648 * #Thread(ThreadGroup,Runnable,String)} with the exception of the fact
649 * that it allows the thread stack size to be specified. The stack size
650 * is the approximate number of bytes of address space that the virtual
651 * machine is to allocate for this thread's stack. <b>The effect of the
652 * {@code stackSize} parameter, if any, is highly platform dependent.</b>
653 *
654 * <p>On some platforms, specifying a higher value for the
655 * {@code stackSize} parameter may allow a thread to achieve greater
656 * recursion depth before throwing a {@link StackOverflowError}.
657 * Similarly, specifying a lower value may allow a greater number of
658 * threads to exist concurrently without throwing an {@link
659 * OutOfMemoryError} (or other internal error). The details of
660 * the relationship between the value of the {@code stackSize} parameter
661 * and the maximum recursion depth and concurrency level are
662 * platform-dependent. <b>On some platforms, the value of the
663 * {@code stackSize} parameter may have no effect whatsoever.</b>
664 *
665 * <p>The virtual machine is free to treat the {@code stackSize}
666 * parameter as a suggestion. If the specified value is unreasonably low
667 * for the platform, the virtual machine may instead use some
668 * platform-specific minimum value; if the specified value is unreasonably
669 * high, the virtual machine may instead use some platform-specific
670 * maximum. Likewise, the virtual machine is free to round the specified
671 * value up or down as it sees fit (or to ignore it completely).
672 *
673 * <p>Specifying a value of zero for the {@code stackSize} parameter will
674 * cause this constructor to behave exactly like the
675 * {@code Thread(ThreadGroup, Runnable, String)} constructor.
676 *
677 * <p><i>Due to the platform-dependent nature of the behavior of this
678 * constructor, extreme care should be exercised in its use.
679 * The thread stack size necessary to perform a given computation will
680 * likely vary from one JRE implementation to another. In light of this
681 * variation, careful tuning of the stack size parameter may be required,
682 * and the tuning may need to be repeated for each JRE implementation on
683 * which an application is to run.</i>
684 *
685 * <p>Implementation note: Java platform implementers are encouraged to
686 * document their implementation's behavior with respect to the
687 * {@code stackSize} parameter.
688 *
689 *
690 * @param group
691 * the thread group. If {@code null} and there is a security
692 * manager, the group is determined by {@linkplain
693 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
694 * If there is not a security manager or {@code
695 * SecurityManager.getThreadGroup()} returns {@code null}, the group
696 * is set to the current thread's thread group.
697 *
698 * @param target
699 * the object whose {@code run} method is invoked when this thread
700 * is started. If {@code null}, this thread's run method is invoked.
701 *
702 * @param name
703 * the name of the new thread
704 *
705 * @param stackSize
706 * the desired stack size for the new thread, or zero to indicate
707 * that this parameter is to be ignored.
708 *
709 * @throws SecurityException
710 * if the current thread cannot create a thread in the specified
711 * thread group
712 *
713 * @since 1.4
714 */
715 public Thread(ThreadGroup group, Runnable target, String name,
716 long stackSize) {
717 init(group, target, name, stackSize);
718 }
719
720 /**
721 * Allocates a new {@code Thread} object so that it has {@code target}
722 * as its run object, has the specified {@code name} as its name,
723 * belongs to the thread group referred to by {@code group}, has
724 * the specified {@code stackSize}, and inherits initial values for
725 * {@linkplain InheritableThreadLocal inheritable thread-local} variables
726 * if {@code inheritThreadLocals} is {@code true}.
727 *
728 * <p> This constructor is identical to {@link
729 * #Thread(ThreadGroup,Runnable,String,long)} with the added ability to
730 * suppress, or not, the inheriting of initial values for inheritable
731 * thread-local variables from the constructing thread. This allows for
732 * finer grain control over inheritable thread-locals. Care must be taken
733 * when passing a value of {@code false} for {@code inheritThreadLocals},
734 * as it may lead to unexpected behavior if the new thread executes code
735 * that expects a specific thread-local value to be inherited.
736 *
737 * <p> Specifying a value of {@code true} for the {@code inheritThreadLocals}
738 * parameter will cause this constructor to behave exactly like the
739 * {@code Thread(ThreadGroup, Runnable, String, long)} constructor.
740 *
741 * @param group
742 * the thread group. If {@code null} and there is a security
743 * manager, the group is determined by {@linkplain
744 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
745 * If there is not a security manager or {@code
746 * SecurityManager.getThreadGroup()} returns {@code null}, the group
747 * is set to the current thread's thread group.
748 *
749 * @param target
750 * the object whose {@code run} method is invoked when this thread
751 * is started. If {@code null}, this thread's run method is invoked.
752 *
753 * @param name
754 * the name of the new thread
755 *
756 * @param stackSize
757 * the desired stack size for the new thread, or zero to indicate
758 * that this parameter is to be ignored
759 *
760 * @param inheritThreadLocals
761 * if {@code true}, inherit initial values for inheritable
762 * thread-locals from the constructing thread, otherwise no initial
763 * values are inherited
764 *
765 * @throws SecurityException
766 * if the current thread cannot create a thread in the specified
767 * thread group
768 *
769 * @since 9
770 */
771 public Thread(ThreadGroup group, Runnable target, String name,
772 long stackSize, boolean inheritThreadLocals) {
773 init(group, target, name, stackSize, null, inheritThreadLocals);
774 }
775
776 /**
777 * Causes this thread to begin execution; the Java Virtual Machine
778 * calls the <code>run</code> method of this thread.
779 * <p>
780 * The result is that two threads are running concurrently: the
781 * current thread (which returns from the call to the
782 * <code>start</code> method) and the other thread (which executes its
783 * <code>run</code> method).
784 * <p>
785 * It is never legal to start a thread more than once.
786 * In particular, a thread may not be restarted once it has completed
787 * execution.
788 *
789 * @exception IllegalThreadStateException if the thread was already
790 * started.
791 * @see #run()
792 * @see #stop()
793 */
794 public synchronized void start() {
795 /**
796 * This method is not invoked for the main method thread or "system"
797 * group threads created/set up by the VM. Any new functionality added
798 * to this method in the future may have to also be added to the VM.
799 *
800 * A zero status value corresponds to state "NEW".
801 */
802 if (threadStatus != 0)
803 throw new IllegalThreadStateException();
804
805 /* Notify the group that this thread is about to be started
806 * so that it can be added to the group's list of threads
807 * and the group's unstarted count can be decremented. */
808 group.add(this);
809
810 boolean started = false;
811 try {
812 start0();
813 started = true;
814 } finally {
815 try {
816 if (!started) {
817 group.threadStartFailed(this);
818 }
819 } catch (Throwable ignore) {
820 /* do nothing. If start0 threw a Throwable then
821 it will be passed up the call stack */
822 }
823 }
824 }
825
826 private native void start0();
827
828 /**
829 * If this thread was constructed using a separate
830 * <code>Runnable</code> run object, then that
831 * <code>Runnable</code> object's <code>run</code> method is called;
832 * otherwise, this method does nothing and returns.
833 * <p>
834 * Subclasses of <code>Thread</code> should override this method.
835 *
836 * @see #start()
837 * @see #stop()
838 * @see #Thread(ThreadGroup, Runnable, String)
839 */
840 @Override
841 public void run() {
842 if (target != null) {
843 target.run();
844 }
845 }
846
847 /**
848 * This method is called by the system to give a Thread
849 * a chance to clean up before it actually exits.
850 */
851 private void exit() {
852 if (group != null) {
853 group.threadTerminated(this);
854 group = null;
855 }
856 /* Aggressively null out all reference fields: see bug 4006245 */
857 target = null;
858 /* Speed the release of some of these resources */
859 threadLocals = null;
860 inheritableThreadLocals = null;
861 inheritedAccessControlContext = null;
862 blocker = null;
863 uncaughtExceptionHandler = null;
864 }
865
866 /**
867 * Forces the thread to stop executing.
868 * <p>
869 * If there is a security manager installed, its <code>checkAccess</code>
870 * method is called with <code>this</code>
871 * as its argument. This may result in a
872 * <code>SecurityException</code> being raised (in the current thread).
873 * <p>
874 * If this thread is different from the current thread (that is, the current
875 * thread is trying to stop a thread other than itself), the
876 * security manager's <code>checkPermission</code> method (with a
877 * <code>RuntimePermission("stopThread")</code> argument) is called in
878 * addition.
879 * Again, this may result in throwing a
880 * <code>SecurityException</code> (in the current thread).
881 * <p>
882 * The thread represented by this thread is forced to stop whatever
883 * it is doing abnormally and to throw a newly created
884 * <code>ThreadDeath</code> object as an exception.
885 * <p>
886 * It is permitted to stop a thread that has not yet been started.
887 * If the thread is eventually started, it immediately terminates.
888 * <p>
889 * An application should not normally try to catch
890 * <code>ThreadDeath</code> unless it must do some extraordinary
891 * cleanup operation (note that the throwing of
892 * <code>ThreadDeath</code> causes <code>finally</code> clauses of
893 * <code>try</code> statements to be executed before the thread
894 * officially dies). If a <code>catch</code> clause catches a
895 * <code>ThreadDeath</code> object, it is important to rethrow the
896 * object so that the thread actually dies.
897 * <p>
898 * The top-level error handler that reacts to otherwise uncaught
899 * exceptions does not print out a message or otherwise notify the
900 * application if the uncaught exception is an instance of
901 * <code>ThreadDeath</code>.
902 *
903 * @exception SecurityException if the current thread cannot
904 * modify this thread.
905 * @see #interrupt()
906 * @see #checkAccess()
907 * @see #run()
908 * @see #start()
909 * @see ThreadDeath
910 * @see ThreadGroup#uncaughtException(Thread,Throwable)
911 * @see SecurityManager#checkAccess(Thread)
912 * @see SecurityManager#checkPermission
913 * @deprecated This method is inherently unsafe. Stopping a thread with
914 * Thread.stop causes it to unlock all of the monitors that it
915 * has locked (as a natural consequence of the unchecked
916 * <code>ThreadDeath</code> exception propagating up the stack). If
917 * any of the objects previously protected by these monitors were in
918 * an inconsistent state, the damaged objects become visible to
919 * other threads, potentially resulting in arbitrary behavior. Many
920 * uses of <code>stop</code> should be replaced by code that simply
921 * modifies some variable to indicate that the target thread should
922 * stop running. The target thread should check this variable
923 * regularly, and return from its run method in an orderly fashion
924 * if the variable indicates that it is to stop running. If the
925 * target thread waits for long periods (on a condition variable,
926 * for example), the <code>interrupt</code> method should be used to
927 * interrupt the wait.
928 * For more information, see
929 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
930 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
931 */
932 @Deprecated(since="1.2")
933 public final void stop() {
934 SecurityManager security = System.getSecurityManager();
935 if (security != null) {
936 checkAccess();
937 if (this != Thread.currentThread()) {
938 security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
939 }
940 }
941 // A zero status value corresponds to "NEW", it can't change to
942 // not-NEW because we hold the lock.
943 if (threadStatus != 0) {
944 resume(); // Wake up thread if it was suspended; no-op otherwise
945 }
946
947 // The VM can handle all thread states
948 stop0(new ThreadDeath());
949 }
950
951 /**
952 * Throws {@code UnsupportedOperationException}.
953 *
954 * @param obj ignored
955 *
956 * @deprecated This method was originally designed to force a thread to stop
957 * and throw a given {@code Throwable} as an exception. It was
958 * inherently unsafe (see {@link #stop()} for details), and furthermore
959 * could be used to generate exceptions that the target thread was
960 * not prepared to handle.
961 * For more information, see
962 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
963 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
964 * This method is subject to removal in a future version of Java SE.
965 */
966 @Deprecated(since="1.2", forRemoval=true)
967 public final synchronized void stop(Throwable obj) {
968 throw new UnsupportedOperationException();
969 }
970
971 /**
972 * Interrupts this thread.
973 *
974 * <p> Unless the current thread is interrupting itself, which is
975 * always permitted, the {@link #checkAccess() checkAccess} method
976 * of this thread is invoked, which may cause a {@link
977 * SecurityException} to be thrown.
978 *
979 * <p> If this thread is blocked in an invocation of the {@link
980 * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
981 * Object#wait(long, int) wait(long, int)} methods of the {@link Object}
982 * class, or of the {@link #join()}, {@link #join(long)}, {@link
983 * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
984 * methods of this class, then its interrupt status will be cleared and it
985 * will receive an {@link InterruptedException}.
986 *
987 * <p> If this thread is blocked in an I/O operation upon an {@link
988 * java.nio.channels.InterruptibleChannel InterruptibleChannel}
989 * then the channel will be closed, the thread's interrupt
990 * status will be set, and the thread will receive a {@link
991 * java.nio.channels.ClosedByInterruptException}.
992 *
993 * <p> If this thread is blocked in a {@link java.nio.channels.Selector}
994 * then the thread's interrupt status will be set and it will return
995 * immediately from the selection operation, possibly with a non-zero
996 * value, just as if the selector's {@link
997 * java.nio.channels.Selector#wakeup wakeup} method were invoked.
998 *
999 * <p> If none of the previous conditions hold then this thread's interrupt
1000 * status will be set. </p>
1001 *
1002 * <p> Interrupting a thread that is not alive need not have any effect.
1003 *
1004 * @throws SecurityException
1005 * if the current thread cannot modify this thread
1006 *
1007 * @revised 6.0
1008 * @spec JSR-51
1009 */
1010 public void interrupt() {
1011 if (this != Thread.currentThread())
1012 checkAccess();
1013
1014 synchronized (blockerLock) {
1015 Interruptible b = blocker;
1016 if (b != null) {
1017 interrupt0(); // Just to set the interrupt flag
1018 b.interrupt(this);
1019 return;
1020 }
1021 }
1022 interrupt0();
1023 }
1024
1025 /**
1026 * Tests whether the current thread has been interrupted. The
1027 * <i>interrupted status</i> of the thread is cleared by this method. In
1028 * other words, if this method were to be called twice in succession, the
1029 * second call would return false (unless the current thread were
1030 * interrupted again, after the first call had cleared its interrupted
1031 * status and before the second call had examined it).
1032 *
1033 * <p>A thread interruption ignored because a thread was not alive
1034 * at the time of the interrupt will be reflected by this method
1035 * returning false.
1036 *
1037 * @return <code>true</code> if the current thread has been interrupted;
1038 * <code>false</code> otherwise.
1039 * @see #isInterrupted()
1040 * @revised 6.0
1041 */
1042 public static boolean interrupted() {
1043 return currentThread().isInterrupted(true);
1044 }
1045
1046 /**
1047 * Tests whether this thread has been interrupted. The <i>interrupted
1048 * status</i> of the thread is unaffected by this method.
1049 *
1050 * <p>A thread interruption ignored because a thread was not alive
1051 * at the time of the interrupt will be reflected by this method
1052 * returning false.
1053 *
1054 * @return <code>true</code> if this thread has been interrupted;
1055 * <code>false</code> otherwise.
1056 * @see #interrupted()
1057 * @revised 6.0
1058 */
1059 public boolean isInterrupted() {
1060 return isInterrupted(false);
1061 }
1062
1063 /**
1064 * Tests if some Thread has been interrupted. The interrupted state
1065 * is reset or not based on the value of ClearInterrupted that is
1066 * passed.
1067 */
1068 @HotSpotIntrinsicCandidate
1069 private native boolean isInterrupted(boolean ClearInterrupted);
1070
1071 /**
1072 * Throws {@link NoSuchMethodError}.
1073 *
1074 * @deprecated This method was originally designed to destroy this
1075 * thread without any cleanup. Any monitors it held would have
1076 * remained locked. However, the method was never implemented.
1077 * If it were to be implemented, it would be deadlock-prone in
1078 * much the manner of {@link #suspend}. If the target thread held
1079 * a lock protecting a critical system resource when it was
1080 * destroyed, no thread could ever access this resource again.
1081 * If another thread ever attempted to lock this resource, deadlock
1082 * would result. Such deadlocks typically manifest themselves as
1083 * "frozen" processes. For more information, see
1084 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">
1085 * Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1086 * This method is subject to removal in a future version of Java SE.
1087 * @throws NoSuchMethodError always
1088 */
1089 @Deprecated(since="1.5", forRemoval=true)
1090 public void destroy() {
1091 throw new NoSuchMethodError();
1092 }
1093
1094 /**
1095 * Tests if this thread is alive. A thread is alive if it has
1096 * been started and has not yet died.
1097 *
1098 * @return <code>true</code> if this thread is alive;
1099 * <code>false</code> otherwise.
1100 */
1101 public final native boolean isAlive();
1102
1103 /**
1104 * Suspends this thread.
1105 * <p>
1106 * First, the <code>checkAccess</code> method of this thread is called
1107 * with no arguments. This may result in throwing a
1108 * <code>SecurityException </code>(in the current thread).
1109 * <p>
1110 * If the thread is alive, it is suspended and makes no further
1111 * progress unless and until it is resumed.
1112 *
1113 * @exception SecurityException if the current thread cannot modify
1114 * this thread.
1115 * @see #checkAccess
1116 * @deprecated This method has been deprecated, as it is
1117 * inherently deadlock-prone. If the target thread holds a lock on the
1118 * monitor protecting a critical system resource when it is suspended, no
1119 * thread can access this resource until the target thread is resumed. If
1120 * the thread that would resume the target thread attempts to lock this
1121 * monitor prior to calling <code>resume</code>, deadlock results. Such
1122 * deadlocks typically manifest themselves as "frozen" processes.
1123 * For more information, see
1124 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
1125 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1126 */
1127 @Deprecated(since="1.2")
1128 public final void suspend() {
1129 checkAccess();
1130 suspend0();
1131 }
1132
1133 /**
1134 * Resumes a suspended thread.
1135 * <p>
1136 * First, the <code>checkAccess</code> method of this thread is called
1137 * with no arguments. This may result in throwing a
1138 * <code>SecurityException</code> (in the current thread).
1139 * <p>
1140 * If the thread is alive but suspended, it is resumed and is
1141 * permitted to make progress in its execution.
1142 *
1143 * @exception SecurityException if the current thread cannot modify this
1144 * thread.
1145 * @see #checkAccess
1146 * @see #suspend()
1147 * @deprecated This method exists solely for use with {@link #suspend},
1148 * which has been deprecated because it is deadlock-prone.
1149 * For more information, see
1150 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
1151 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1152 */
1153 @Deprecated(since="1.2")
1154 public final void resume() {
1155 checkAccess();
1156 resume0();
1157 }
1158
1159 /**
1160 * Changes the priority of this thread.
1161 * <p>
1162 * First the <code>checkAccess</code> method of this thread is called
1163 * with no arguments. This may result in throwing a
1164 * <code>SecurityException</code>.
1165 * <p>
1166 * Otherwise, the priority of this thread is set to the smaller of
1167 * the specified <code>newPriority</code> and the maximum permitted
1168 * priority of the thread's thread group.
1169 *
1170 * @param newPriority priority to set this thread to
1171 * @exception IllegalArgumentException If the priority is not in the
1172 * range <code>MIN_PRIORITY</code> to
1173 * <code>MAX_PRIORITY</code>.
1174 * @exception SecurityException if the current thread cannot modify
1175 * this thread.
1176 * @see #getPriority
1177 * @see #checkAccess()
1178 * @see #getThreadGroup()
1179 * @see #MAX_PRIORITY
1180 * @see #MIN_PRIORITY
1181 * @see ThreadGroup#getMaxPriority()
1182 */
1183 public final void setPriority(int newPriority) {
1184 ThreadGroup g;
1185 checkAccess();
1186 if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
1187 throw new IllegalArgumentException();
1188 }
1189 if((g = getThreadGroup()) != null) {
1190 if (newPriority > g.getMaxPriority()) {
1191 newPriority = g.getMaxPriority();
1192 }
1193 setPriority0(priority = newPriority);
1194 }
1195 }
1196
1197 /**
1198 * Returns this thread's priority.
1199 *
1200 * @return this thread's priority.
1201 * @see #setPriority
1202 */
1203 public final int getPriority() {
1204 return priority;
1205 }
1206
1207 /**
1208 * Changes the name of this thread to be equal to the argument
1209 * <code>name</code>.
1210 * <p>
1211 * First the <code>checkAccess</code> method of this thread is called
1212 * with no arguments. This may result in throwing a
1213 * <code>SecurityException</code>.
1214 *
1215 * @param name the new name for this thread.
1216 * @exception SecurityException if the current thread cannot modify this
1217 * thread.
1218 * @see #getName
1219 * @see #checkAccess()
1220 */
1221 public final synchronized void setName(String name) {
1222 checkAccess();
1223 if (name == null) {
1224 throw new NullPointerException("name cannot be null");
1225 }
1226
1227 this.name = name;
1228 if (threadStatus != 0) {
1229 setNativeName(name);
1230 }
1231 }
1232
1233 /**
1234 * Returns this thread's name.
1235 *
1236 * @return this thread's name.
1237 * @see #setName(String)
1238 */
1239 public final String getName() {
1240 return name;
1241 }
1242
1243 /**
1244 * Returns the thread group to which this thread belongs.
1245 * This method returns null if this thread has died
1246 * (been stopped).
1247 *
1248 * @return this thread's thread group.
1249 */
1250 public final ThreadGroup getThreadGroup() {
1251 return group;
1252 }
1253
1254 /**
1255 * Returns an estimate of the number of active threads in the current
1256 * thread's {@linkplain java.lang.ThreadGroup thread group} and its
1257 * subgroups. Recursively iterates over all subgroups in the current
1258 * thread's thread group.
1259 *
1260 * <p> The value returned is only an estimate because the number of
1261 * threads may change dynamically while this method traverses internal
1262 * data structures, and might be affected by the presence of certain
1263 * system threads. This method is intended primarily for debugging
1264 * and monitoring purposes.
1265 *
1266 * @return an estimate of the number of active threads in the current
1267 * thread's thread group and in any other thread group that
1268 * has the current thread's thread group as an ancestor
1269 */
1270 public static int activeCount() {
1271 return currentThread().getThreadGroup().activeCount();
1272 }
1273
1274 /**
1275 * Copies into the specified array every active thread in the current
1276 * thread's thread group and its subgroups. This method simply
1277 * invokes the {@link java.lang.ThreadGroup#enumerate(Thread[])}
1278 * method of the current thread's thread group.
1279 *
1280 * <p> An application might use the {@linkplain #activeCount activeCount}
1281 * method to get an estimate of how big the array should be, however
1282 * <i>if the array is too short to hold all the threads, the extra threads
1283 * are silently ignored.</i> If it is critical to obtain every active
1284 * thread in the current thread's thread group and its subgroups, the
1285 * invoker should verify that the returned int value is strictly less
1286 * than the length of {@code tarray}.
1287 *
1288 * <p> Due to the inherent race condition in this method, it is recommended
1289 * that the method only be used for debugging and monitoring purposes.
1290 *
1291 * @param tarray
1292 * an array into which to put the list of threads
1293 *
1294 * @return the number of threads put into the array
1295 *
1296 * @throws SecurityException
1297 * if {@link java.lang.ThreadGroup#checkAccess} determines that
1298 * the current thread cannot access its thread group
1299 */
1300 public static int enumerate(Thread tarray[]) {
1301 return currentThread().getThreadGroup().enumerate(tarray);
1302 }
1303
1304 /**
1305 * Counts the number of stack frames in this thread. The thread must
1306 * be suspended.
1307 *
1308 * @return the number of stack frames in this thread.
1309 * @exception IllegalThreadStateException if this thread is not
1310 * suspended.
1311 * @deprecated The definition of this call depends on {@link #suspend},
1312 * which is deprecated. Further, the results of this call
1313 * were never well-defined.
1314 * This method is subject to removal in a future version of Java SE.
1315 * @see StackWalker
1316 */
1317 @Deprecated(since="1.2", forRemoval=true)
1318 public native int countStackFrames();
1319
1320 /**
1321 * Waits at most {@code millis} milliseconds for this thread to
1322 * die. A timeout of {@code 0} means to wait forever.
1323 *
1324 * <p> This implementation uses a loop of {@code this.wait} calls
1325 * conditioned on {@code this.isAlive}. As a thread terminates the
1326 * {@code this.notifyAll} method is invoked. It is recommended that
1327 * applications not use {@code wait}, {@code notify}, or
1328 * {@code notifyAll} on {@code Thread} instances.
1329 *
1330 * @param millis
1331 * the time to wait in milliseconds
1332 *
1333 * @throws IllegalArgumentException
1334 * if the value of {@code millis} is negative
1335 *
1336 * @throws InterruptedException
1337 * if any thread has interrupted the current thread. The
1338 * <i>interrupted status</i> of the current thread is
1339 * cleared when this exception is thrown.
1340 */
1341 public final synchronized void join(long millis)
1342 throws InterruptedException {
1343 long base = System.currentTimeMillis();
1344 long now = 0;
1345
1346 if (millis < 0) {
1347 throw new IllegalArgumentException("timeout value is negative");
1348 }
1349
1350 if (millis == 0) {
1351 while (isAlive()) {
1352 wait(0);
1353 }
1354 } else {
1355 while (isAlive()) {
1356 long delay = millis - now;
1357 if (delay <= 0) {
1358 break;
1359 }
1360 wait(delay);
1361 now = System.currentTimeMillis() - base;
1362 }
1363 }
1364 }
1365
1366 /**
1367 * Waits at most {@code millis} milliseconds plus
1368 * {@code nanos} nanoseconds for this thread to die.
1369 *
1370 * <p> This implementation uses a loop of {@code this.wait} calls
1371 * conditioned on {@code this.isAlive}. As a thread terminates the
1372 * {@code this.notifyAll} method is invoked. It is recommended that
1373 * applications not use {@code wait}, {@code notify}, or
1374 * {@code notifyAll} on {@code Thread} instances.
1375 *
1376 * @param millis
1377 * the time to wait in milliseconds
1378 *
1379 * @param nanos
1380 * {@code 0-999999} additional nanoseconds to wait
1381 *
1382 * @throws IllegalArgumentException
1383 * if the value of {@code millis} is negative, or the value
1384 * of {@code nanos} is not in the range {@code 0-999999}
1385 *
1386 * @throws InterruptedException
1387 * if any thread has interrupted the current thread. The
1388 * <i>interrupted status</i> of the current thread is
1389 * cleared when this exception is thrown.
1390 */
1391 public final synchronized void join(long millis, int nanos)
1392 throws InterruptedException {
1393
1394 if (millis < 0) {
1395 throw new IllegalArgumentException("timeout value is negative");
1396 }
1397
1398 if (nanos < 0 || nanos > 999999) {
1399 throw new IllegalArgumentException(
1400 "nanosecond timeout value out of range");
1401 }
1402
1403 if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
1404 millis++;
1405 }
1406
1407 join(millis);
1408 }
1409
1410 /**
1411 * Waits for this thread to die.
1412 *
1413 * <p> An invocation of this method behaves in exactly the same
1414 * way as the invocation
1415 *
1416 * <blockquote>
1417 * {@linkplain #join(long) join}{@code (0)}
1418 * </blockquote>
1419 *
1420 * @throws InterruptedException
1421 * if any thread has interrupted the current thread. The
1422 * <i>interrupted status</i> of the current thread is
1423 * cleared when this exception is thrown.
1424 */
1425 public final void join() throws InterruptedException {
1426 join(0);
1427 }
1428
1429 /**
1430 * Prints a stack trace of the current thread to the standard error stream.
1431 * This method is used only for debugging.
1432 */
1433 public static void dumpStack() {
1434 new Exception("Stack trace").printStackTrace();
1435 }
1436
1437 /**
1438 * Marks this thread as either a {@linkplain #isDaemon daemon} thread
1439 * or a user thread. The Java Virtual Machine exits when the only
1440 * threads running are all daemon threads.
1441 *
1442 * <p> This method must be invoked before the thread is started.
1443 *
1444 * @param on
1445 * if {@code true}, marks this thread as a daemon thread
1446 *
1447 * @throws IllegalThreadStateException
1448 * if this thread is {@linkplain #isAlive alive}
1449 *
1450 * @throws SecurityException
1451 * if {@link #checkAccess} determines that the current
1452 * thread cannot modify this thread
1453 */
1454 public final void setDaemon(boolean on) {
1455 checkAccess();
1456 if (isAlive()) {
1457 throw new IllegalThreadStateException();
1458 }
1459 daemon = on;
1460 }
1461
1462 /**
1463 * Tests if this thread is a daemon thread.
1464 *
1465 * @return <code>true</code> if this thread is a daemon thread;
1466 * <code>false</code> otherwise.
1467 * @see #setDaemon(boolean)
1468 */
1469 public final boolean isDaemon() {
1470 return daemon;
1471 }
1472
1473 /**
1474 * Determines if the currently running thread has permission to
1475 * modify this thread.
1476 * <p>
1477 * If there is a security manager, its <code>checkAccess</code> method
1478 * is called with this thread as its argument. This may result in
1479 * throwing a <code>SecurityException</code>.
1480 *
1481 * @exception SecurityException if the current thread is not allowed to
1482 * access this thread.
1483 * @see SecurityManager#checkAccess(Thread)
1484 */
1485 public final void checkAccess() {
1486 SecurityManager security = System.getSecurityManager();
1487 if (security != null) {
1488 security.checkAccess(this);
1489 }
1490 }
1491
1492 /**
1493 * Returns a string representation of this thread, including the
1494 * thread's name, priority, and thread group.
1495 *
1496 * @return a string representation of this thread.
1497 */
1498 public String toString() {
1499 ThreadGroup group = getThreadGroup();
1500 if (group != null) {
1501 return "Thread[" + getName() + "," + getPriority() + "," +
1502 group.getName() + "]";
1503 } else {
1504 return "Thread[" + getName() + "," + getPriority() + "," +
1505 "" + "]";
1506 }
1507 }
1508
1509 /**
1510 * Returns the context ClassLoader for this Thread. The context
1511 * ClassLoader is provided by the creator of the thread for use
1512 * by code running in this thread when loading classes and resources.
1513 * If not {@linkplain #setContextClassLoader set}, the default is the
1514 * ClassLoader context of the parent Thread. The context ClassLoader of the
1515 * primordial thread is typically set to the class loader used to load the
1516 * application.
1517 *
1518 * <p>If a security manager is present, and the invoker's class loader is not
1519 * {@code null} and is not the same as or an ancestor of the context class
1520 * loader, then this method invokes the security manager's {@link
1521 * SecurityManager#checkPermission(java.security.Permission) checkPermission}
1522 * method with a {@link RuntimePermission RuntimePermission}{@code
1523 * ("getClassLoader")} permission to verify that retrieval of the context
1524 * class loader is permitted.
1525 *
1526 * @return the context ClassLoader for this Thread, or {@code null}
1527 * indicating the system class loader (or, failing that, the
1528 * bootstrap class loader)
1529 *
1530 * @throws SecurityException
1531 * if the current thread cannot get the context ClassLoader
1532 *
1533 * @since 1.2
1534 */
1535 @CallerSensitive
1536 public ClassLoader getContextClassLoader() {
1537 if (contextClassLoader == null)
1538 return null;
1539 SecurityManager sm = System.getSecurityManager();
1540 if (sm != null) {
1541 ClassLoader.checkClassLoaderPermission(contextClassLoader,
1542 Reflection.getCallerClass());
1543 }
1544 return contextClassLoader;
1545 }
1546
1547 /**
1548 * Sets the context ClassLoader for this Thread. The context
1549 * ClassLoader can be set when a thread is created, and allows
1550 * the creator of the thread to provide the appropriate class loader,
1551 * through {@code getContextClassLoader}, to code running in the thread
1552 * when loading classes and resources.
1553 *
1554 * <p>If a security manager is present, its {@link
1555 * SecurityManager#checkPermission(java.security.Permission) checkPermission}
1556 * method is invoked with a {@link RuntimePermission RuntimePermission}{@code
1557 * ("setContextClassLoader")} permission to see if setting the context
1558 * ClassLoader is permitted.
1559 *
1560 * @param cl
1561 * the context ClassLoader for this Thread, or null indicating the
1562 * system class loader (or, failing that, the bootstrap class loader)
1563 *
1564 * @throws SecurityException
1565 * if the current thread cannot set the context ClassLoader
1566 *
1567 * @since 1.2
1568 */
1569 public void setContextClassLoader(ClassLoader cl) {
1570 SecurityManager sm = System.getSecurityManager();
1571 if (sm != null) {
1572 sm.checkPermission(new RuntimePermission("setContextClassLoader"));
1573 }
1574 contextClassLoader = cl;
1575 }
1576
1577 /**
1578 * Returns {@code true} if and only if the current thread holds the
1579 * monitor lock on the specified object.
1580 *
1581 * <p>This method is designed to allow a program to assert that
1582 * the current thread already holds a specified lock:
1583 * <pre>
1584 * assert Thread.holdsLock(obj);
1585 * </pre>
1586 *
1587 * @param obj the object on which to test lock ownership
1588 * @throws NullPointerException if obj is {@code null}
1589 * @return {@code true} if the current thread holds the monitor lock on
1590 * the specified object.
1591 * @since 1.4
1592 */
1593 public static native boolean holdsLock(Object obj);
1594
1595 private static final StackTraceElement[] EMPTY_STACK_TRACE
1596 = new StackTraceElement[0];
1597
1598 /**
1599 * Returns an array of stack trace elements representing the stack dump
1600 * of this thread. This method will return a zero-length array if
1601 * this thread has not started, has started but has not yet been
1602 * scheduled to run by the system, or has terminated.
1603 * If the returned array is of non-zero length then the first element of
1604 * the array represents the top of the stack, which is the most recent
1605 * method invocation in the sequence. The last element of the array
1606 * represents the bottom of the stack, which is the least recent method
1607 * invocation in the sequence.
1608 *
1609 * <p>If there is a security manager, and this thread is not
1610 * the current thread, then the security manager's
1611 * {@code checkPermission} method is called with a
1612 * {@code RuntimePermission("getStackTrace")} permission
1613 * to see if it's ok to get the stack trace.
1614 *
1615 * <p>Some virtual machines may, under some circumstances, omit one
1616 * or more stack frames from the stack trace. In the extreme case,
1617 * a virtual machine that has no stack trace information concerning
1618 * this thread is permitted to return a zero-length array from this
1619 * method.
1620 *
1621 * @return an array of {@code StackTraceElement},
1622 * each represents one stack frame.
1623 *
1624 * @throws SecurityException
1625 * if a security manager exists and its
1626 * {@code checkPermission} method doesn't allow
1627 * getting the stack trace of thread.
1628 * @see SecurityManager#checkPermission
1629 * @see RuntimePermission
1630 * @see Throwable#getStackTrace
1631 *
1632 * @since 1.5
1633 */
1634 public StackTraceElement[] getStackTrace() {
1635 if (this != Thread.currentThread()) {
1636 // check for getStackTrace permission
1637 SecurityManager security = System.getSecurityManager();
1638 if (security != null) {
1639 security.checkPermission(
1640 SecurityConstants.GET_STACK_TRACE_PERMISSION);
1641 }
1642 // optimization so we do not call into the vm for threads that
1643 // have not yet started or have terminated
1644 if (!isAlive()) {
1645 return EMPTY_STACK_TRACE;
1646 }
1647 StackTraceElement[][] stackTraceArray = dumpThreads(new Thread[] {this});
1648 StackTraceElement[] stackTrace = stackTraceArray[0];
1649 // a thread that was alive during the previous isAlive call may have
1650 // since terminated, therefore not having a stacktrace.
1651 if (stackTrace == null) {
1652 stackTrace = EMPTY_STACK_TRACE;
1653 }
1654 return stackTrace;
1655 } else {
1656 return (new Exception()).getStackTrace();
1657 }
1658 }
1659
1660 /**
1661 * Returns a map of stack traces for all live threads.
1662 * The map keys are threads and each map value is an array of
1663 * {@code StackTraceElement} that represents the stack dump
1664 * of the corresponding {@code Thread}.
1665 * The returned stack traces are in the format specified for
1666 * the {@link #getStackTrace getStackTrace} method.
1667 *
1668 * <p>The threads may be executing while this method is called.
1669 * The stack trace of each thread only represents a snapshot and
1670 * each stack trace may be obtained at different time. A zero-length
1671 * array will be returned in the map value if the virtual machine has
1672 * no stack trace information about a thread.
1673 *
1674 * <p>If there is a security manager, then the security manager's
1675 * {@code checkPermission} method is called with a
1676 * {@code RuntimePermission("getStackTrace")} permission as well as
1677 * {@code RuntimePermission("modifyThreadGroup")} permission
1678 * to see if it is ok to get the stack trace of all threads.
1679 *
1680 * @return a {@code Map} from {@code Thread} to an array of
1681 * {@code StackTraceElement} that represents the stack trace of
1682 * the corresponding thread.
1683 *
1684 * @throws SecurityException
1685 * if a security manager exists and its
1686 * {@code checkPermission} method doesn't allow
1687 * getting the stack trace of thread.
1688 * @see #getStackTrace
1689 * @see SecurityManager#checkPermission
1690 * @see RuntimePermission
1691 * @see Throwable#getStackTrace
1692 *
1693 * @since 1.5
1694 */
1695 public static Map<Thread, StackTraceElement[]> getAllStackTraces() {
1696 // check for getStackTrace permission
1697 SecurityManager security = System.getSecurityManager();
1698 if (security != null) {
1699 security.checkPermission(
1700 SecurityConstants.GET_STACK_TRACE_PERMISSION);
1701 security.checkPermission(
1702 SecurityConstants.MODIFY_THREADGROUP_PERMISSION);
1703 }
1704
1705 // Get a snapshot of the list of all threads
1706 Thread[] threads = getThreads();
1707 StackTraceElement[][] traces = dumpThreads(threads);
1708 Map<Thread, StackTraceElement[]> m = new HashMap<>(threads.length);
1709 for (int i = 0; i < threads.length; i++) {
1710 StackTraceElement[] stackTrace = traces[i];
1711 if (stackTrace != null) {
1712 m.put(threads[i], stackTrace);
1713 }
1714 // else terminated so we don't put it in the map
1715 }
1716 return m;
1717 }
1718
1719
1720 private static final RuntimePermission SUBCLASS_IMPLEMENTATION_PERMISSION =
1721 new RuntimePermission("enableContextClassLoaderOverride");
1722
1723 /** cache of subclass security audit results */
1724 /* Replace with ConcurrentReferenceHashMap when/if it appears in a future
1725 * release */
1726 private static class Caches {
1727 /** cache of subclass security audit results */
1728 static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits =
1729 new ConcurrentHashMap<>();
1730
1731 /** queue for WeakReferences to audited subclasses */
1732 static final ReferenceQueue<Class<?>> subclassAuditsQueue =
1733 new ReferenceQueue<>();
1734 }
1735
1736 /**
1737 * Verifies that this (possibly subclass) instance can be constructed
1738 * without violating security constraints: the subclass must not override
1739 * security-sensitive non-final methods, or else the
1740 * "enableContextClassLoaderOverride" RuntimePermission is checked.
1741 */
1742 private static boolean isCCLOverridden(Class<?> cl) {
1743 if (cl == Thread.class)
1744 return false;
1745
1746 processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits);
1747 WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue);
1748 Boolean result = Caches.subclassAudits.get(key);
1749 if (result == null) {
1750 result = Boolean.valueOf(auditSubclass(cl));
1751 Caches.subclassAudits.putIfAbsent(key, result);
1752 }
1753
1754 return result.booleanValue();
1755 }
1756
1757 /**
1758 * Performs reflective checks on given subclass to verify that it doesn't
1759 * override security-sensitive non-final methods. Returns true if the
1760 * subclass overrides any of the methods, false otherwise.
1761 */
1762 private static boolean auditSubclass(final Class<?> subcl) {
1763 Boolean result = AccessController.doPrivileged(
1764 new PrivilegedAction<>() {
1765 public Boolean run() {
1766 for (Class<?> cl = subcl;
1767 cl != Thread.class;
1768 cl = cl.getSuperclass())
1769 {
1770 try {
1771 cl.getDeclaredMethod("getContextClassLoader", new Class<?>[0]);
1772 return Boolean.TRUE;
1773 } catch (NoSuchMethodException ex) {
1774 }
1775 try {
1776 Class<?>[] params = {ClassLoader.class};
1777 cl.getDeclaredMethod("setContextClassLoader", params);
1778 return Boolean.TRUE;
1779 } catch (NoSuchMethodException ex) {
1780 }
1781 }
1782 return Boolean.FALSE;
1783 }
1784 }
1785 );
1786 return result.booleanValue();
1787 }
1788
1789 private static native StackTraceElement[][] dumpThreads(Thread[] threads);
1790 private static native Thread[] getThreads();
1791
1792 /**
1793 * Returns the identifier of this Thread. The thread ID is a positive
1794 * {@code long} number generated when this thread was created.
1795 * The thread ID is unique and remains unchanged during its lifetime.
1796 * When a thread is terminated, this thread ID may be reused.
1797 *
1798 * @return this thread's ID.
1799 * @since 1.5
1800 */
1801 public long getId() {
1802 return tid;
1803 }
1804
1805 /**
1806 * A thread state. A thread can be in one of the following states:
1807 * <ul>
1808 * <li>{@link #NEW}<br>
1809 * A thread that has not yet started is in this state.
1810 * </li>
1811 * <li>{@link #RUNNABLE}<br>
1812 * A thread executing in the Java virtual machine is in this state.
1813 * </li>
1814 * <li>{@link #BLOCKED}<br>
1815 * A thread that is blocked waiting for a monitor lock
1816 * is in this state.
1817 * </li>
1818 * <li>{@link #WAITING}<br>
1819 * A thread that is waiting indefinitely for another thread to
1820 * perform a particular action is in this state.
1821 * </li>
1822 * <li>{@link #TIMED_WAITING}<br>
1823 * A thread that is waiting for another thread to perform an action
1824 * for up to a specified waiting time is in this state.
1825 * </li>
1826 * <li>{@link #TERMINATED}<br>
1827 * A thread that has exited is in this state.
1828 * </li>
1829 * </ul>
1830 *
1831 * <p>
1832 * A thread can be in only one state at a given point in time.
1833 * These states are virtual machine states which do not reflect
1834 * any operating system thread states.
1835 *
1836 * @since 1.5
1837 * @see #getState
1838 */
1839 public enum State {
1840 /**
1841 * Thread state for a thread which has not yet started.
1842 */
1843 NEW,
1844
1845 /**
1846 * Thread state for a runnable thread. A thread in the runnable
1847 * state is executing in the Java virtual machine but it may
1848 * be waiting for other resources from the operating system
1849 * such as processor.
1850 */
1851 RUNNABLE,
1852
1853 /**
1854 * Thread state for a thread blocked waiting for a monitor lock.
1855 * A thread in the blocked state is waiting for a monitor lock
1856 * to enter a synchronized block/method or
1857 * reenter a synchronized block/method after calling
1858 * {@link Object#wait() Object.wait}.
1859 */
1860 BLOCKED,
1861
1862 /**
1863 * Thread state for a waiting thread.
1864 * A thread is in the waiting state due to calling one of the
1865 * following methods:
1866 * <ul>
1867 * <li>{@link Object#wait() Object.wait} with no timeout</li>
1868 * <li>{@link #join() Thread.join} with no timeout</li>
1869 * <li>{@link LockSupport#park() LockSupport.park}</li>
1870 * </ul>
1871 *
1872 * <p>A thread in the waiting state is waiting for another thread to
1873 * perform a particular action.
1874 *
1875 * For example, a thread that has called {@code Object.wait()}
1876 * on an object is waiting for another thread to call
1877 * {@code Object.notify()} or {@code Object.notifyAll()} on
1878 * that object. A thread that has called {@code Thread.join()}
1879 * is waiting for a specified thread to terminate.
1880 */
1881 WAITING,
1882
1883 /**
1884 * Thread state for a waiting thread with a specified waiting time.
1885 * A thread is in the timed waiting state due to calling one of
1886 * the following methods with a specified positive waiting time:
1887 * <ul>
1888 * <li>{@link #sleep Thread.sleep}</li>
1889 * <li>{@link Object#wait(long) Object.wait} with timeout</li>
1890 * <li>{@link #join(long) Thread.join} with timeout</li>
1891 * <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
1892 * <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
1893 * </ul>
1894 */
1895 TIMED_WAITING,
1896
1897 /**
1898 * Thread state for a terminated thread.
1899 * The thread has completed execution.
1900 */
1901 TERMINATED;
1902 }
1903
1904 /**
1905 * Returns the state of this thread.
1906 * This method is designed for use in monitoring of the system state,
1907 * not for synchronization control.
1908 *
1909 * @return this thread's state.
1910 * @since 1.5
1911 */
1912 public State getState() {
1913 // get current thread state
1914 return jdk.internal.misc.VM.toThreadState(threadStatus);
1915 }
1916
1917 // Added in JSR-166
1918
1919 /**
1920 * Interface for handlers invoked when a {@code Thread} abruptly
1921 * terminates due to an uncaught exception.
1922 * <p>When a thread is about to terminate due to an uncaught exception
1923 * the Java Virtual Machine will query the thread for its
1924 * {@code UncaughtExceptionHandler} using
1925 * {@link #getUncaughtExceptionHandler} and will invoke the handler's
1926 * {@code uncaughtException} method, passing the thread and the
1927 * exception as arguments.
1928 * If a thread has not had its {@code UncaughtExceptionHandler}
1929 * explicitly set, then its {@code ThreadGroup} object acts as its
1930 * {@code UncaughtExceptionHandler}. If the {@code ThreadGroup} object
1931 * has no
1932 * special requirements for dealing with the exception, it can forward
1933 * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler
1934 * default uncaught exception handler}.
1935 *
1936 * @see #setDefaultUncaughtExceptionHandler
1937 * @see #setUncaughtExceptionHandler
1938 * @see ThreadGroup#uncaughtException
1939 * @since 1.5
1940 */
1941 @FunctionalInterface
1942 public interface UncaughtExceptionHandler {
1943 /**
1944 * Method invoked when the given thread terminates due to the
1945 * given uncaught exception.
1946 * <p>Any exception thrown by this method will be ignored by the
1947 * Java Virtual Machine.
1948 * @param t the thread
1949 * @param e the exception
1950 */
1951 void uncaughtException(Thread t, Throwable e);
1952 }
1953
1954 // null unless explicitly set
1955 private volatile UncaughtExceptionHandler uncaughtExceptionHandler;
1956
1957 // null unless explicitly set
1958 private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler;
1959
1960 /**
1961 * Set the default handler invoked when a thread abruptly terminates
1962 * due to an uncaught exception, and no other handler has been defined
1963 * for that thread.
1964 *
1965 * <p>Uncaught exception handling is controlled first by the thread, then
1966 * by the thread's {@link ThreadGroup} object and finally by the default
1967 * uncaught exception handler. If the thread does not have an explicit
1968 * uncaught exception handler set, and the thread's thread group
1969 * (including parent thread groups) does not specialize its
1970 * {@code uncaughtException} method, then the default handler's
1971 * {@code uncaughtException} method will be invoked.
1972 * <p>By setting the default uncaught exception handler, an application
1973 * can change the way in which uncaught exceptions are handled (such as
1974 * logging to a specific device, or file) for those threads that would
1975 * already accept whatever "default" behavior the system
1976 * provided.
1977 *
1978 * <p>Note that the default uncaught exception handler should not usually
1979 * defer to the thread's {@code ThreadGroup} object, as that could cause
1980 * infinite recursion.
1981 *
1982 * @param eh the object to use as the default uncaught exception handler.
1983 * If {@code null} then there is no default handler.
1984 *
1985 * @throws SecurityException if a security manager is present and it denies
1986 * {@link RuntimePermission}{@code ("setDefaultUncaughtExceptionHandler")}
1987 *
1988 * @see #setUncaughtExceptionHandler
1989 * @see #getUncaughtExceptionHandler
1990 * @see ThreadGroup#uncaughtException
1991 * @since 1.5
1992 */
1993 public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
1994 SecurityManager sm = System.getSecurityManager();
1995 if (sm != null) {
1996 sm.checkPermission(
1997 new RuntimePermission("setDefaultUncaughtExceptionHandler")
1998 );
1999 }
2000
2001 defaultUncaughtExceptionHandler = eh;
2002 }
2003
2004 /**
2005 * Returns the default handler invoked when a thread abruptly terminates
2006 * due to an uncaught exception. If the returned value is {@code null},
2007 * there is no default.
2008 * @since 1.5
2009 * @see #setDefaultUncaughtExceptionHandler
2010 * @return the default uncaught exception handler for all threads
2011 */
2012 public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler(){
2013 return defaultUncaughtExceptionHandler;
2014 }
2015
2016 /**
2017 * Returns the handler invoked when this thread abruptly terminates
2018 * due to an uncaught exception. If this thread has not had an
2019 * uncaught exception handler explicitly set then this thread's
2020 * {@code ThreadGroup} object is returned, unless this thread
2021 * has terminated, in which case {@code null} is returned.
2022 * @since 1.5
2023 * @return the uncaught exception handler for this thread
2024 */
2025 public UncaughtExceptionHandler getUncaughtExceptionHandler() {
2026 return uncaughtExceptionHandler != null ?
2027 uncaughtExceptionHandler : group;
2028 }
2029
2030 /**
2031 * Set the handler invoked when this thread abruptly terminates
2032 * due to an uncaught exception.
2033 * <p>A thread can take full control of how it responds to uncaught
2034 * exceptions by having its uncaught exception handler explicitly set.
2035 * If no such handler is set then the thread's {@code ThreadGroup}
2036 * object acts as its handler.
2037 * @param eh the object to use as this thread's uncaught exception
2038 * handler. If {@code null} then this thread has no explicit handler.
2039 * @throws SecurityException if the current thread is not allowed to
2040 * modify this thread.
2041 * @see #setDefaultUncaughtExceptionHandler
2042 * @see ThreadGroup#uncaughtException
2043 * @since 1.5
2044 */
2045 public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
2046 checkAccess();
2047 uncaughtExceptionHandler = eh;
2048 }
2049
2050 /**
2051 * Dispatch an uncaught exception to the handler. This method is
2052 * intended to be called only by the JVM.
2053 */
2054 private void dispatchUncaughtException(Throwable e) {
2055 getUncaughtExceptionHandler().uncaughtException(this, e);
2056 }
2057
2058 /**
2059 * Removes from the specified map any keys that have been enqueued
2060 * on the specified reference queue.
2061 */
2062 static void processQueue(ReferenceQueue<Class<?>> queue,
2063 ConcurrentMap<? extends
2064 WeakReference<Class<?>>, ?> map)
2065 {
2066 Reference<? extends Class<?>> ref;
2067 while((ref = queue.poll()) != null) {
2068 map.remove(ref);
2069 }
2070 }
2071
2072 /**
2073 * Weak key for Class objects.
2074 **/
2075 static class WeakClassKey extends WeakReference<Class<?>> {
2076 /**
2077 * saved value of the referent's identity hash code, to maintain
2078 * a consistent hash code after the referent has been cleared
2079 */
2080 private final int hash;
2081
2082 /**
2083 * Create a new WeakClassKey to the given object, registered
2084 * with a queue.
2085 */
2086 WeakClassKey(Class<?> cl, ReferenceQueue<Class<?>> refQueue) {
2087 super(cl, refQueue);
2088 hash = System.identityHashCode(cl);
2089 }
2090
2091 /**
2092 * Returns the identity hash code of the original referent.
2093 */
2094 @Override
2095 public int hashCode() {
2096 return hash;
2097 }
2098
2099 /**
2100 * Returns true if the given object is this identical
2101 * WeakClassKey instance, or, if this object's referent has not
2102 * been cleared, if the given object is another WeakClassKey
2103 * instance with the identical non-null referent as this one.
2104 */
2105 @Override
2106 public boolean equals(Object obj) {
2107 if (obj == this)
2108 return true;
2109
2110 if (obj instanceof WeakClassKey) {
2111 Object referent = get();
2112 return (referent != null) &&
2113 (referent == ((WeakClassKey) obj).get());
2114 } else {
2115 return false;
2116 }
2117 }
2118 }
2119
2120
2121 // The following three initially uninitialized fields are exclusively
2122 // managed by class java.util.concurrent.ThreadLocalRandom. These
2123 // fields are used to build the high-performance PRNGs in the
2124 // concurrent code, and we can not risk accidental false sharing.
2125 // Hence, the fields are isolated with @Contended.
2126
2127 /** The current seed for a ThreadLocalRandom */
2128 @jdk.internal.vm.annotation.Contended("tlr")
2129 long threadLocalRandomSeed;
2130
2131 /** Probe hash value; nonzero if threadLocalRandomSeed initialized */
2132 @jdk.internal.vm.annotation.Contended("tlr")
2133 int threadLocalRandomProbe;
2134
2135 /** Secondary seed isolated from public ThreadLocalRandom sequence */
2136 @jdk.internal.vm.annotation.Contended("tlr")
2137 int threadLocalRandomSecondarySeed;
2138
2139 /* Some private helper methods */
2140 private native void setPriority0(int newPriority);
2141 private native void stop0(Object o);
2142 private native void suspend0();
2143 private native void resume0();
2144 private native void interrupt0();
2145 private native void setNativeName(String name);
2146 }