1 /*
2 * Copyright (c) 1994, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. 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} 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} 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} method of class {@code Runtime} 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} method or by
69 * throwing an exception that propagates beyond the {@code run}
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}. This
75 * subclass should override the {@code run} method of class
76 * {@code Thread}. 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} interface. That class then
101 * implements the {@code run} method. An instance of the class can
102 * then be allocated, passed as an argument when creating
103 * {@code Thread}, 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 the thread is a daemon thread. */
154 private boolean daemon = false;
155
156 /* JVM state */
157 private boolean stillborn = false;
158
159 /* What will be run. */
160 private Runnable target;
161
162 /* The group of this thread */
163 private ThreadGroup group;
164
165 /* The context ClassLoader for this thread */
166 private ClassLoader contextClassLoader;
167
168 /* The inherited AccessControlContext of this thread */
169 private AccessControlContext inheritedAccessControlContext;
170
171 /* For autonumbering anonymous threads. */
172 private static int threadInitNumber;
173 private static synchronized int nextThreadNum() {
174 return threadInitNumber++;
175 }
176
177 /* ThreadLocal values pertaining to this thread. This map is maintained
178 * by the ThreadLocal class. */
179 ThreadLocal.ThreadLocalMap threadLocals = null;
180
181 /*
182 * InheritableThreadLocal values pertaining to this thread. This map is
183 * maintained by the InheritableThreadLocal class.
184 */
185 ThreadLocal.ThreadLocalMap inheritableThreadLocals = null;
186
187 /*
188 * The requested stack size for this thread, or 0 if the creator did
189 * not specify a stack size. It is up to the VM to do whatever it
190 * likes with this number; some VMs will ignore it.
191 */
192 private long stackSize;
193
194 /*
195 * JVM-private state that persists after native thread termination.
196 */
197 private long nativeParkEventPointer;
198
199 /*
200 * Thread ID
201 */
202 private long tid;
203
204 /* For generating thread ID */
205 private static long threadSeqNumber;
206
207 /*
208 * Java thread status for tools, default indicates thread 'not yet started'
209 */
210 private volatile int threadStatus;
211
212 private static synchronized long nextThreadID() {
213 return ++threadSeqNumber;
214 }
215
216 /**
217 * The argument supplied to the current call to
218 * java.util.concurrent.locks.LockSupport.park.
219 * Set by (private) java.util.concurrent.locks.LockSupport.setBlocker
220 * Accessed using java.util.concurrent.locks.LockSupport.getBlocker
221 */
222 volatile Object parkBlocker;
223
224 /* The object in which this thread is blocked in an interruptible I/O
225 * operation, if any. The blocker's interrupt method should be invoked
226 * after setting this thread's interrupt status.
227 */
228 private volatile Interruptible blocker;
229 private final Object blockerLock = new Object();
230
231 /* Set the blocker field; invoked via jdk.internal.misc.SharedSecrets
232 * from java.nio code
233 */
234 static void blockedOn(Interruptible b) {
235 Thread me = Thread.currentThread();
236 synchronized (me.blockerLock) {
237 me.blocker = b;
238 }
239 }
240
241 /**
242 * The minimum priority that a thread can have.
243 */
244 public static final int MIN_PRIORITY = 1;
245
246 /**
247 * The default priority that is assigned to a thread.
248 */
249 public static final int NORM_PRIORITY = 5;
250
251 /**
252 * The maximum priority that a thread can have.
253 */
254 public static final int MAX_PRIORITY = 10;
255
256 /**
257 * Returns a reference to the currently executing thread object.
258 *
259 * @return the currently executing thread.
260 */
261 @HotSpotIntrinsicCandidate
262 public static native Thread currentThread();
263
264 /**
265 * A hint to the scheduler that the current thread is willing to yield
266 * its current use of a processor. The scheduler is free to ignore this
267 * hint.
268 *
269 * <p> Yield is a heuristic attempt to improve relative progression
270 * between threads that would otherwise over-utilise a CPU. Its use
271 * should be combined with detailed profiling and benchmarking to
272 * ensure that it actually has the desired effect.
273 *
274 * <p> It is rarely appropriate to use this method. It may be useful
275 * for debugging or testing purposes, where it may help to reproduce
276 * bugs due to race conditions. It may also be useful when designing
277 * concurrency control constructs such as the ones in the
278 * {@link java.util.concurrent.locks} package.
279 */
280 public static native void yield();
281
282 /**
283 * Causes the currently executing thread to sleep (temporarily cease
284 * execution) for the specified number of milliseconds, subject to
285 * the precision and accuracy of system timers and schedulers. The thread
286 * does not lose ownership of any monitors.
287 *
288 * @param millis
289 * the length of time to sleep in milliseconds
290 *
291 * @throws IllegalArgumentException
292 * if the value of {@code millis} is negative
293 *
294 * @throws InterruptedException
295 * if any thread has interrupted the current thread. The
296 * <i>interrupted status</i> of the current thread is
297 * cleared when this exception is thrown.
298 */
299 public static native void sleep(long millis) throws InterruptedException;
300
301 /**
302 * Causes the currently executing thread to sleep (temporarily cease
303 * execution) for the specified number of milliseconds plus the specified
304 * number of nanoseconds, subject to the precision and accuracy of system
305 * timers and schedulers. The thread does not lose ownership of any
306 * monitors.
307 *
308 * @param millis
309 * the length of time to sleep in milliseconds
310 *
311 * @param nanos
312 * {@code 0-999999} additional nanoseconds to sleep
313 *
314 * @throws IllegalArgumentException
315 * if the value of {@code millis} is negative, or the value of
316 * {@code nanos} is not in the range {@code 0-999999}
317 *
318 * @throws InterruptedException
319 * if any thread has interrupted the current thread. The
320 * <i>interrupted status</i> of the current thread is
321 * cleared when this exception is thrown.
322 */
323 public static void sleep(long millis, int nanos)
324 throws InterruptedException {
325 if (millis < 0) {
326 throw new IllegalArgumentException("timeout value is negative");
327 }
328
329 if (nanos < 0 || nanos > 999999) {
330 throw new IllegalArgumentException(
331 "nanosecond timeout value out of range");
332 }
333
334 if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
335 millis++;
336 }
337
338 sleep(millis);
339 }
340
341 /**
342 * Indicates that the caller is momentarily unable to progress, until the
343 * occurrence of one or more actions on the part of other activities. By
344 * invoking this method within each iteration of a spin-wait loop construct,
345 * the calling thread indicates to the runtime that it is busy-waiting.
346 * The runtime may take action to improve the performance of invoking
347 * spin-wait loop constructions.
348 *
349 * @apiNote
350 * As an example consider a method in a class that spins in a loop until
351 * some flag is set outside of that method. A call to the {@code onSpinWait}
352 * method should be placed inside the spin loop.
353 * <pre>{@code
354 * class EventHandler {
355 * volatile boolean eventNotificationNotReceived;
356 * void waitForEventAndHandleIt() {
357 * while ( eventNotificationNotReceived ) {
358 * java.lang.Thread.onSpinWait();
359 * }
360 * readAndProcessEvent();
361 * }
362 *
363 * void readAndProcessEvent() {
364 * // Read event from some source and process it
365 * . . .
366 * }
367 * }
368 * }</pre>
369 * <p>
370 * The code above would remain correct even if the {@code onSpinWait}
371 * method was not called at all. However on some architectures the Java
372 * Virtual Machine may issue the processor instructions to address such
373 * code patterns in a more beneficial way.
374 *
375 * @since 9
376 */
377 @HotSpotIntrinsicCandidate
378 public static void onSpinWait() {}
379
380 /**
381 * Initializes a Thread with the current AccessControlContext.
382 * @see #init(ThreadGroup,Runnable,String,long,AccessControlContext,boolean)
383 */
384 private void init(ThreadGroup g, Runnable target, String name,
385 long stackSize) {
386 init(g, target, name, stackSize, null, true);
387 }
388
389 /**
390 * Initializes a Thread.
391 *
392 * @param g the Thread group
393 * @param target the object whose run() method gets called
394 * @param name the name of the new Thread
395 * @param stackSize the desired stack size for the new thread, or
396 * zero to indicate that this parameter is to be ignored.
397 * @param acc the AccessControlContext to inherit, or
398 * AccessController.getContext() if null
399 * @param inheritThreadLocals if {@code true}, inherit initial values for
400 * inheritable thread-locals from the constructing thread
401 */
402 private void init(ThreadGroup g, Runnable target, String name,
403 long stackSize, AccessControlContext acc,
404 boolean inheritThreadLocals) {
405 if (name == null) {
406 throw new NullPointerException("name cannot be null");
407 }
408
409 this.name = name;
410
411 Thread parent = currentThread();
412 SecurityManager security = System.getSecurityManager();
413 if (g == null) {
414 /* Determine if it's an applet or not */
415
416 /* If there is a security manager, ask the security manager
417 what to do. */
418 if (security != null) {
419 g = security.getThreadGroup();
420 }
421
422 /* If the security doesn't have a strong opinion of the matter
423 use the parent thread group. */
424 if (g == null) {
425 g = parent.getThreadGroup();
426 }
427 }
428
429 /* checkAccess regardless of whether or not threadgroup is
430 explicitly passed in. */
431 g.checkAccess();
432
433 /*
434 * Do we have the required permissions?
435 */
436 if (security != null) {
437 if (isCCLOverridden(getClass())) {
438 security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
439 }
440 }
441
442 g.addUnstarted();
443
444 this.group = g;
445 this.daemon = parent.isDaemon();
446 this.priority = parent.getPriority();
447 if (security == null || isCCLOverridden(parent.getClass()))
448 this.contextClassLoader = parent.getContextClassLoader();
449 else
450 this.contextClassLoader = parent.contextClassLoader;
451 this.inheritedAccessControlContext =
452 acc != null ? acc : AccessController.getContext();
453 this.target = target;
454 setPriority(priority);
455 if (inheritThreadLocals && parent.inheritableThreadLocals != null)
456 this.inheritableThreadLocals =
457 ThreadLocal.createInheritedMap(parent.inheritableThreadLocals);
458 /* Stash the specified stack size in case the VM cares */
459 this.stackSize = stackSize;
460
461 /* Set thread ID */
462 tid = nextThreadID();
463 }
464
465 /**
466 * Throws CloneNotSupportedException as a Thread can not be meaningfully
467 * cloned. Construct a new Thread instead.
468 *
469 * @throws CloneNotSupportedException
470 * always
471 */
472 @Override
473 protected Object clone() throws CloneNotSupportedException {
474 throw new CloneNotSupportedException();
475 }
476
477 /**
478 * Allocates a new {@code Thread} object. This constructor has the same
479 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
480 * {@code (null, null, gname)}, where {@code gname} is a newly generated
481 * name. Automatically generated names are of the form
482 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
483 */
484 public Thread() {
485 init(null, null, "Thread-" + nextThreadNum(), 0);
486 }
487
488 /**
489 * Allocates a new {@code Thread} object. This constructor has the same
490 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
491 * {@code (null, target, gname)}, where {@code gname} is a newly generated
492 * name. Automatically generated names are of the form
493 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
494 *
495 * @param target
496 * the object whose {@code run} method is invoked when this thread
497 * is started. If {@code null}, this classes {@code run} method does
498 * nothing.
499 */
500 public Thread(Runnable target) {
501 init(null, target, "Thread-" + nextThreadNum(), 0);
502 }
503
504 /**
505 * Creates a new Thread that inherits the given AccessControlContext
506 * but thread-local variables are not inherited.
507 * This is not a public constructor.
508 */
509 Thread(Runnable target, AccessControlContext acc) {
510 init(null, target, "Thread-" + nextThreadNum(), 0, acc, false);
511 }
512
513 /**
514 * Allocates a new {@code Thread} object. This constructor has the same
515 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
516 * {@code (group, target, gname)} ,where {@code gname} is a newly generated
517 * name. Automatically generated names are of the form
518 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
519 *
520 * @param group
521 * the thread group. If {@code null} and there is a security
522 * manager, the group is determined by {@linkplain
523 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
524 * If there is not a security manager or {@code
525 * SecurityManager.getThreadGroup()} returns {@code null}, the group
526 * is set to the current thread's thread group.
527 *
528 * @param target
529 * the object whose {@code run} method is invoked when this thread
530 * is started. If {@code null}, this thread's run method is invoked.
531 *
532 * @throws SecurityException
533 * if the current thread cannot create a thread in the specified
534 * thread group
535 */
536 public Thread(ThreadGroup group, Runnable target) {
537 init(group, target, "Thread-" + nextThreadNum(), 0);
538 }
539
540 /**
541 * Allocates a new {@code Thread} object. This constructor has the same
542 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
543 * {@code (null, null, name)}.
544 *
545 * @param name
546 * the name of the new thread
547 */
548 public Thread(String name) {
549 init(null, null, name, 0);
550 }
551
552 /**
553 * Allocates a new {@code Thread} object. This constructor has the same
554 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
555 * {@code (group, null, name)}.
556 *
557 * @param group
558 * the thread group. If {@code null} and there is a security
559 * manager, the group is determined by {@linkplain
560 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
561 * If there is not a security manager or {@code
562 * SecurityManager.getThreadGroup()} returns {@code null}, the group
563 * is set to the current thread's thread group.
564 *
565 * @param name
566 * the name of the new thread
567 *
568 * @throws SecurityException
569 * if the current thread cannot create a thread in the specified
570 * thread group
571 */
572 public Thread(ThreadGroup group, String name) {
573 init(group, null, name, 0);
574 }
575
576 /**
577 * Allocates a new {@code Thread} object. This constructor has the same
578 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
579 * {@code (null, target, name)}.
580 *
581 * @param target
582 * the object whose {@code run} method is invoked when this thread
583 * is started. If {@code null}, this thread's run method is invoked.
584 *
585 * @param name
586 * the name of the new thread
587 */
588 public Thread(Runnable target, String name) {
589 init(null, target, name, 0);
590 }
591
592 /**
593 * Allocates a new {@code Thread} object so that it has {@code target}
594 * as its run object, has the specified {@code name} as its name,
595 * and belongs to the thread group referred to by {@code group}.
596 *
597 * <p>If there is a security manager, its
598 * {@link SecurityManager#checkAccess(ThreadGroup) checkAccess}
599 * method is invoked with the ThreadGroup as its argument.
600 *
601 * <p>In addition, its {@code checkPermission} method is invoked with
602 * the {@code RuntimePermission("enableContextClassLoaderOverride")}
603 * permission when invoked directly or indirectly by the constructor
604 * of a subclass which overrides the {@code getContextClassLoader}
605 * or {@code setContextClassLoader} methods.
606 *
607 * <p>The priority of the newly created thread is set equal to the
608 * priority of the thread creating it, that is, the currently running
609 * thread. The method {@linkplain #setPriority setPriority} may be
610 * used to change the priority to a new value.
611 *
612 * <p>The newly created thread is initially marked as being a daemon
613 * thread if and only if the thread creating it is currently marked
614 * as a daemon thread. The method {@linkplain #setDaemon setDaemon}
615 * may be used to change whether or not a thread is a daemon.
616 *
617 * @param group
618 * the thread group. If {@code null} and there is a security
619 * manager, the group is determined by {@linkplain
620 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
621 * If there is not a security manager or {@code
622 * SecurityManager.getThreadGroup()} returns {@code null}, the group
623 * is set to the current thread's thread group.
624 *
625 * @param target
626 * the object whose {@code run} method is invoked when this thread
627 * is started. If {@code null}, this thread's run method is invoked.
628 *
629 * @param name
630 * the name of the new thread
631 *
632 * @throws SecurityException
633 * if the current thread cannot create a thread in the specified
634 * thread group or cannot override the context class loader methods.
635 */
636 public Thread(ThreadGroup group, Runnable target, String name) {
637 init(group, target, name, 0);
638 }
639
640 /**
641 * Allocates a new {@code Thread} object so that it has {@code target}
642 * as its run object, has the specified {@code name} as its name,
643 * and belongs to the thread group referred to by {@code group}, and has
644 * the specified <i>stack size</i>.
645 *
646 * <p>This constructor is identical to {@link
647 * #Thread(ThreadGroup,Runnable,String)} with the exception of the fact
648 * that it allows the thread stack size to be specified. The stack size
649 * is the approximate number of bytes of address space that the virtual
650 * machine is to allocate for this thread's stack. <b>The effect of the
651 * {@code stackSize} parameter, if any, is highly platform dependent.</b>
652 *
653 * <p>On some platforms, specifying a higher value for the
654 * {@code stackSize} parameter may allow a thread to achieve greater
655 * recursion depth before throwing a {@link StackOverflowError}.
656 * Similarly, specifying a lower value may allow a greater number of
657 * threads to exist concurrently without throwing an {@link
658 * OutOfMemoryError} (or other internal error). The details of
659 * the relationship between the value of the {@code stackSize} parameter
660 * and the maximum recursion depth and concurrency level are
661 * platform-dependent. <b>On some platforms, the value of the
662 * {@code stackSize} parameter may have no effect whatsoever.</b>
663 *
664 * <p>The virtual machine is free to treat the {@code stackSize}
665 * parameter as a suggestion. If the specified value is unreasonably low
666 * for the platform, the virtual machine may instead use some
667 * platform-specific minimum value; if the specified value is unreasonably
668 * high, the virtual machine may instead use some platform-specific
669 * maximum. Likewise, the virtual machine is free to round the specified
670 * value up or down as it sees fit (or to ignore it completely).
671 *
672 * <p>Specifying a value of zero for the {@code stackSize} parameter will
673 * cause this constructor to behave exactly like the
674 * {@code Thread(ThreadGroup, Runnable, String)} constructor.
675 *
676 * <p><i>Due to the platform-dependent nature of the behavior of this
677 * constructor, extreme care should be exercised in its use.
678 * The thread stack size necessary to perform a given computation will
679 * likely vary from one JRE implementation to another. In light of this
680 * variation, careful tuning of the stack size parameter may be required,
681 * and the tuning may need to be repeated for each JRE implementation on
682 * which an application is to run.</i>
683 *
684 * <p>Implementation note: Java platform implementers are encouraged to
685 * document their implementation's behavior with respect to the
686 * {@code stackSize} parameter.
687 *
688 *
689 * @param group
690 * the thread group. If {@code null} and there is a security
691 * manager, the group is determined by {@linkplain
692 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
693 * If there is not a security manager or {@code
694 * SecurityManager.getThreadGroup()} returns {@code null}, the group
695 * is set to the current thread's thread group.
696 *
697 * @param target
698 * the object whose {@code run} method is invoked when this thread
699 * is started. If {@code null}, this thread's run method is invoked.
700 *
701 * @param name
702 * the name of the new thread
703 *
704 * @param stackSize
705 * the desired stack size for the new thread, or zero to indicate
706 * that this parameter is to be ignored.
707 *
708 * @throws SecurityException
709 * if the current thread cannot create a thread in the specified
710 * thread group
711 *
712 * @since 1.4
713 */
714 public Thread(ThreadGroup group, Runnable target, String name,
715 long stackSize) {
716 init(group, target, name, stackSize);
717 }
718
719 /**
720 * Allocates a new {@code Thread} object so that it has {@code target}
721 * as its run object, has the specified {@code name} as its name,
722 * belongs to the thread group referred to by {@code group}, has
723 * the specified {@code stackSize}, and inherits initial values for
724 * {@linkplain InheritableThreadLocal inheritable thread-local} variables
725 * if {@code inheritThreadLocals} is {@code true}.
726 *
727 * <p> This constructor is identical to {@link
728 * #Thread(ThreadGroup,Runnable,String,long)} with the added ability to
729 * suppress, or not, the inheriting of initial values for inheritable
730 * thread-local variables from the constructing thread. This allows for
731 * finer grain control over inheritable thread-locals. Care must be taken
732 * when passing a value of {@code false} for {@code inheritThreadLocals},
733 * as it may lead to unexpected behavior if the new thread executes code
734 * that expects a specific thread-local value to be inherited.
735 *
736 * <p> Specifying a value of {@code true} for the {@code inheritThreadLocals}
737 * parameter will cause this constructor to behave exactly like the
738 * {@code Thread(ThreadGroup, Runnable, String, long)} constructor.
739 *
740 * @param group
741 * the thread group. If {@code null} and there is a security
742 * manager, the group is determined by {@linkplain
743 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
744 * If there is not a security manager or {@code
745 * SecurityManager.getThreadGroup()} returns {@code null}, the group
746 * is set to the current thread's thread group.
747 *
748 * @param target
749 * the object whose {@code run} method is invoked when this thread
750 * is started. If {@code null}, this thread's run method is invoked.
751 *
752 * @param name
753 * the name of the new thread
754 *
755 * @param stackSize
756 * the desired stack size for the new thread, or zero to indicate
757 * that this parameter is to be ignored
758 *
759 * @param inheritThreadLocals
760 * if {@code true}, inherit initial values for inheritable
761 * thread-locals from the constructing thread, otherwise no initial
762 * values are inherited
763 *
764 * @throws SecurityException
765 * if the current thread cannot create a thread in the specified
766 * thread group
767 *
768 * @since 9
769 */
770 public Thread(ThreadGroup group, Runnable target, String name,
771 long stackSize, boolean inheritThreadLocals) {
772 init(group, target, name, stackSize, null, inheritThreadLocals);
773 }
774
775 /**
776 * Causes this thread to begin execution; the Java Virtual Machine
777 * calls the {@code run} method of this thread.
778 * <p>
779 * The result is that two threads are running concurrently: the
780 * current thread (which returns from the call to the
781 * {@code start} method) and the other thread (which executes its
782 * {@code run} method).
783 * <p>
784 * It is never legal to start a thread more than once.
785 * In particular, a thread may not be restarted once it has completed
786 * execution.
787 *
788 * @throws IllegalThreadStateException if the thread was already started.
789 * @see #run()
790 * @see #stop()
791 */
792 public synchronized void start() {
793 /**
794 * This method is not invoked for the main method thread or "system"
795 * group threads created/set up by the VM. Any new functionality added
796 * to this method in the future may have to also be added to the VM.
797 *
798 * A zero status value corresponds to state "NEW".
799 */
800 if (threadStatus != 0)
801 throw new IllegalThreadStateException();
802
803 /* Notify the group that this thread is about to be started
804 * so that it can be added to the group's list of threads
805 * and the group's unstarted count can be decremented. */
806 group.add(this);
807
808 boolean started = false;
809 try {
810 start0();
811 started = true;
812 } finally {
813 try {
814 if (!started) {
815 group.threadStartFailed(this);
816 }
817 } catch (Throwable ignore) {
818 /* do nothing. If start0 threw a Throwable then
819 it will be passed up the call stack */
820 }
821 }
822 }
823
824 private native void start0();
825
826 /**
827 * If this thread was constructed using a separate
828 * {@code Runnable} run object, then that
829 * {@code Runnable} object's {@code run} method is called;
830 * otherwise, this method does nothing and returns.
831 * <p>
832 * Subclasses of {@code Thread} should override this method.
833 *
834 * @see #start()
835 * @see #stop()
836 * @see #Thread(ThreadGroup, Runnable, String)
837 */
838 @Override
839 public void run() {
840 if (target != null) {
841 target.run();
842 }
843 }
844
845 /**
846 * This method is called by the system to give a Thread
847 * a chance to clean up before it actually exits.
848 */
849 private void exit() {
850 if (group != null) {
851 group.threadTerminated(this);
852 group = null;
853 }
854 /* Aggressively null out all reference fields: see bug 4006245 */
855 target = null;
856 /* Speed the release of some of these resources */
857 threadLocals = null;
858 inheritableThreadLocals = null;
859 inheritedAccessControlContext = null;
860 blocker = null;
861 uncaughtExceptionHandler = null;
862 }
863
864 /**
865 * Forces the thread to stop executing.
866 * <p>
867 * If there is a security manager installed, its {@code checkAccess}
868 * method is called with {@code this}
869 * as its argument. This may result in a
870 * {@code SecurityException} being raised (in the current thread).
871 * <p>
872 * If this thread is different from the current thread (that is, the current
873 * thread is trying to stop a thread other than itself), the
874 * security manager's {@code checkPermission} method (with a
875 * {@code RuntimePermission("stopThread")} argument) is called in
876 * addition.
877 * Again, this may result in throwing a
878 * {@code SecurityException} (in the current thread).
879 * <p>
880 * The thread represented by this thread is forced to stop whatever
881 * it is doing abnormally and to throw a newly created
882 * {@code ThreadDeath} object as an exception.
883 * <p>
884 * It is permitted to stop a thread that has not yet been started.
885 * If the thread is eventually started, it immediately terminates.
886 * <p>
887 * An application should not normally try to catch
888 * {@code ThreadDeath} unless it must do some extraordinary
889 * cleanup operation (note that the throwing of
890 * {@code ThreadDeath} causes {@code finally} clauses of
891 * {@code try} statements to be executed before the thread
892 * officially dies). If a {@code catch} clause catches a
893 * {@code ThreadDeath} object, it is important to rethrow the
894 * object so that the thread actually dies.
895 * <p>
896 * The top-level error handler that reacts to otherwise uncaught
897 * exceptions does not print out a message or otherwise notify the
898 * application if the uncaught exception is an instance of
899 * {@code ThreadDeath}.
900 *
901 * @throws SecurityException if the current thread cannot
902 * modify this thread.
903 * @see #interrupt()
904 * @see #checkAccess()
905 * @see #run()
906 * @see #start()
907 * @see ThreadDeath
908 * @see ThreadGroup#uncaughtException(Thread,Throwable)
909 * @see SecurityManager#checkAccess(Thread)
910 * @see SecurityManager#checkPermission
911 * @deprecated This method is inherently unsafe. Stopping a thread with
912 * Thread.stop causes it to unlock all of the monitors that it
913 * has locked (as a natural consequence of the unchecked
914 * {@code ThreadDeath} exception propagating up the stack). If
915 * any of the objects previously protected by these monitors were in
916 * an inconsistent state, the damaged objects become visible to
917 * other threads, potentially resulting in arbitrary behavior. Many
918 * uses of {@code stop} should be replaced by code that simply
919 * modifies some variable to indicate that the target thread should
920 * stop running. The target thread should check this variable
921 * regularly, and return from its run method in an orderly fashion
922 * if the variable indicates that it is to stop running. If the
923 * target thread waits for long periods (on a condition variable,
924 * for example), the {@code interrupt} method should be used to
925 * interrupt the wait.
926 * For more information, see
927 * <a href="{@docRoot}/java/lang/doc-files/threadPrimitiveDeprecation.html">Why
928 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
929 */
930 @Deprecated(since="1.2")
931 public final void stop() {
932 SecurityManager security = System.getSecurityManager();
933 if (security != null) {
934 checkAccess();
935 if (this != Thread.currentThread()) {
936 security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
937 }
938 }
939 // A zero status value corresponds to "NEW", it can't change to
940 // not-NEW because we hold the lock.
941 if (threadStatus != 0) {
942 resume(); // Wake up thread if it was suspended; no-op otherwise
943 }
944
945 // The VM can handle all thread states
946 stop0(new ThreadDeath());
947 }
948
949 /**
950 * Throws {@code UnsupportedOperationException}.
951 *
952 * @param obj ignored
953 *
954 * @deprecated This method was originally designed to force a thread to stop
955 * and throw a given {@code Throwable} as an exception. It was
956 * inherently unsafe (see {@link #stop()} for details), and furthermore
957 * could be used to generate exceptions that the target thread was
958 * not prepared to handle.
959 * For more information, see
960 * <a href="{@docRoot}/java/lang/doc-files/threadPrimitiveDeprecation.html">Why
961 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
962 * This method is subject to removal in a future version of Java SE.
963 */
964 @Deprecated(since="1.2", forRemoval=true)
965 public final synchronized void stop(Throwable obj) {
966 throw new UnsupportedOperationException();
967 }
968
969 /**
970 * Interrupts this thread.
971 *
972 * <p> Unless the current thread is interrupting itself, which is
973 * always permitted, the {@link #checkAccess() checkAccess} method
974 * of this thread is invoked, which may cause a {@link
975 * SecurityException} to be thrown.
976 *
977 * <p> If this thread is blocked in an invocation of the {@link
978 * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
979 * Object#wait(long, int) wait(long, int)} methods of the {@link Object}
980 * class, or of the {@link #join()}, {@link #join(long)}, {@link
981 * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
982 * methods of this class, then its interrupt status will be cleared and it
983 * will receive an {@link InterruptedException}.
984 *
985 * <p> If this thread is blocked in an I/O operation upon an {@link
986 * java.nio.channels.InterruptibleChannel InterruptibleChannel}
987 * then the channel will be closed, the thread's interrupt
988 * status will be set, and the thread will receive a {@link
989 * java.nio.channels.ClosedByInterruptException}.
990 *
991 * <p> If this thread is blocked in a {@link java.nio.channels.Selector}
992 * then the thread's interrupt status will be set and it will return
993 * immediately from the selection operation, possibly with a non-zero
994 * value, just as if the selector's {@link
995 * java.nio.channels.Selector#wakeup wakeup} method were invoked.
996 *
997 * <p> If none of the previous conditions hold then this thread's interrupt
998 * status will be set. </p>
999 *
1000 * <p> Interrupting a thread that is not alive need not have any effect.
1001 *
1002 * @throws SecurityException
1003 * if the current thread cannot modify this thread
1004 *
1005 * @revised 6.0
1006 * @spec JSR-51
1007 */
1008 public void interrupt() {
1009 if (this != Thread.currentThread()) {
1010 checkAccess();
1011
1012 // thread may be blocked in an I/O operation
1013 synchronized (blockerLock) {
1014 Interruptible b = blocker;
1015 if (b != null) {
1016 interrupt0(); // set interrupt status
1017 b.interrupt(this);
1018 return;
1019 }
1020 }
1021 }
1022
1023 // set interrupt status
1024 interrupt0();
1025 }
1026
1027 /**
1028 * Tests whether the current thread has been interrupted. The
1029 * <i>interrupted status</i> of the thread is cleared by this method. In
1030 * other words, if this method were to be called twice in succession, the
1031 * second call would return false (unless the current thread were
1032 * interrupted again, after the first call had cleared its interrupted
1033 * status and before the second call had examined it).
1034 *
1035 * <p>A thread interruption ignored because a thread was not alive
1036 * at the time of the interrupt will be reflected by this method
1037 * returning false.
1038 *
1039 * @return {@code true} if the current thread has been interrupted;
1040 * {@code false} otherwise.
1041 * @see #isInterrupted()
1042 * @revised 6.0
1043 */
1044 public static boolean interrupted() {
1045 return currentThread().isInterrupted(true);
1046 }
1047
1048 /**
1049 * Tests whether this thread has been interrupted. The <i>interrupted
1050 * status</i> of the thread is unaffected by this method.
1051 *
1052 * <p>A thread interruption ignored because a thread was not alive
1053 * at the time of the interrupt will be reflected by this method
1054 * returning false.
1055 *
1056 * @return {@code true} if this thread has been interrupted;
1057 * {@code false} otherwise.
1058 * @see #interrupted()
1059 * @revised 6.0
1060 */
1061 public boolean isInterrupted() {
1062 return isInterrupted(false);
1063 }
1064
1065 /**
1066 * Tests if some Thread has been interrupted. The interrupted state
1067 * is reset or not based on the value of ClearInterrupted that is
1068 * passed.
1069 */
1070 @HotSpotIntrinsicCandidate
1071 private native boolean isInterrupted(boolean ClearInterrupted);
1072
1073 /**
1074 * Throws {@link NoSuchMethodError}.
1075 *
1076 * @deprecated This method was originally designed to destroy this
1077 * thread without any cleanup. Any monitors it held would have
1078 * remained locked. However, the method was never implemented.
1079 * If it were to be implemented, it would be deadlock-prone in
1080 * much the manner of {@link #suspend}. If the target thread held
1081 * a lock protecting a critical system resource when it was
1082 * destroyed, no thread could ever access this resource again.
1083 * If another thread ever attempted to lock this resource, deadlock
1084 * would result. Such deadlocks typically manifest themselves as
1085 * "frozen" processes. For more information, see
1086 * <a href="{@docRoot}/java/lang/doc-files/threadPrimitiveDeprecation.html">
1087 * Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1088 * This method is subject to removal in a future version of Java SE.
1089 * @throws NoSuchMethodError always
1090 */
1091 @Deprecated(since="1.5", forRemoval=true)
1092 public void destroy() {
1093 throw new NoSuchMethodError();
1094 }
1095
1096 /**
1097 * Tests if this thread is alive. A thread is alive if it has
1098 * been started and has not yet died.
1099 *
1100 * @return {@code true} if this thread is alive;
1101 * {@code false} otherwise.
1102 */
1103 public final native boolean isAlive();
1104
1105 /**
1106 * Suspends this thread.
1107 * <p>
1108 * First, the {@code checkAccess} method of this thread is called
1109 * with no arguments. This may result in throwing a
1110 * {@code SecurityException }(in the current thread).
1111 * <p>
1112 * If the thread is alive, it is suspended and makes no further
1113 * progress unless and until it is resumed.
1114 *
1115 * @throws SecurityException if the current thread cannot modify
1116 * this thread.
1117 * @see #checkAccess
1118 * @deprecated This method has been deprecated, as it is
1119 * inherently deadlock-prone. If the target thread holds a lock on the
1120 * monitor protecting a critical system resource when it is suspended, no
1121 * thread can access this resource until the target thread is resumed. If
1122 * the thread that would resume the target thread attempts to lock this
1123 * monitor prior to calling {@code resume}, deadlock results. Such
1124 * deadlocks typically manifest themselves as "frozen" processes.
1125 * For more information, see
1126 * <a href="{@docRoot}/java/lang/doc-files/threadPrimitiveDeprecation.html">Why
1127 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1128 */
1129 @Deprecated(since="1.2")
1130 public final void suspend() {
1131 checkAccess();
1132 suspend0();
1133 }
1134
1135 /**
1136 * Resumes a suspended thread.
1137 * <p>
1138 * First, the {@code checkAccess} method of this thread is called
1139 * with no arguments. This may result in throwing a
1140 * {@code SecurityException} (in the current thread).
1141 * <p>
1142 * If the thread is alive but suspended, it is resumed and is
1143 * permitted to make progress in its execution.
1144 *
1145 * @throws SecurityException if the current thread cannot modify this
1146 * thread.
1147 * @see #checkAccess
1148 * @see #suspend()
1149 * @deprecated This method exists solely for use with {@link #suspend},
1150 * which has been deprecated because it is deadlock-prone.
1151 * For more information, see
1152 * <a href="{@docRoot}/java/lang/doc-files/threadPrimitiveDeprecation.html">Why
1153 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1154 */
1155 @Deprecated(since="1.2")
1156 public final void resume() {
1157 checkAccess();
1158 resume0();
1159 }
1160
1161 /**
1162 * Changes the priority of this thread.
1163 * <p>
1164 * First the {@code checkAccess} method of this thread is called
1165 * with no arguments. This may result in throwing a {@code SecurityException}.
1166 * <p>
1167 * Otherwise, the priority of this thread is set to the smaller of
1168 * the specified {@code newPriority} and the maximum permitted
1169 * priority of the thread's thread group.
1170 *
1171 * @param newPriority priority to set this thread to
1172 * @throws IllegalArgumentException If the priority is not in the
1173 * range {@code MIN_PRIORITY} to
1174 * {@code MAX_PRIORITY}.
1175 * @throws SecurityException if the current thread cannot modify
1176 * this thread.
1177 * @see #getPriority
1178 * @see #checkAccess()
1179 * @see #getThreadGroup()
1180 * @see #MAX_PRIORITY
1181 * @see #MIN_PRIORITY
1182 * @see ThreadGroup#getMaxPriority()
1183 */
1184 public final void setPriority(int newPriority) {
1185 ThreadGroup g;
1186 checkAccess();
1187 if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
1188 throw new IllegalArgumentException();
1189 }
1190 if((g = getThreadGroup()) != null) {
1191 if (newPriority > g.getMaxPriority()) {
1192 newPriority = g.getMaxPriority();
1193 }
1194 setPriority0(priority = newPriority);
1195 }
1196 }
1197
1198 /**
1199 * Returns this thread's priority.
1200 *
1201 * @return this thread's priority.
1202 * @see #setPriority
1203 */
1204 public final int getPriority() {
1205 return priority;
1206 }
1207
1208 /**
1209 * Changes the name of this thread to be equal to the argument {@code name}.
1210 * <p>
1211 * First the {@code checkAccess} method of this thread is called
1212 * with no arguments. This may result in throwing a
1213 * {@code SecurityException}.
1214 *
1215 * @param name the new name for this thread.
1216 * @throws 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 * @throws 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} if this thread is a daemon thread;
1466 * {@code false} 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} method
1478 * is called with this thread as its argument. This may result in
1479 * throwing a {@code SecurityException}.
1480 *
1481 * @throws 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 {@code ClassLoader} for this thread. The context
1511 * {@code 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 * {@code ClassLoader} context of the parent thread. The context
1515 * {@code ClassLoader} of the
1516 * primordial thread is typically set to the class loader used to load the
1517 * application.
1518 *
1519 *
1520 * @return the context {@code ClassLoader} for this thread, or {@code null}
1521 * indicating the system class loader (or, failing that, the
1522 * bootstrap class loader)
1523 *
1524 * @throws SecurityException
1525 * if a security manager is present, and the caller's class loader
1526 * is not {@code null} and is not the same as or an ancestor of the
1527 * context class loader, and the caller does not have the
1528 * {@link RuntimePermission}{@code ("getClassLoader")}
1529 *
1530 * @since 1.2
1531 */
1532 @CallerSensitive
1533 public ClassLoader getContextClassLoader() {
1534 if (contextClassLoader == null)
1535 return null;
1536 SecurityManager sm = System.getSecurityManager();
1537 if (sm != null) {
1538 ClassLoader.checkClassLoaderPermission(contextClassLoader,
1539 Reflection.getCallerClass());
1540 }
1541 return contextClassLoader;
1542 }
1543
1544 /**
1545 * Sets the context ClassLoader for this Thread. The context
1546 * ClassLoader can be set when a thread is created, and allows
1547 * the creator of the thread to provide the appropriate class loader,
1548 * through {@code getContextClassLoader}, to code running in the thread
1549 * when loading classes and resources.
1550 *
1551 * <p>If a security manager is present, its {@link
1552 * SecurityManager#checkPermission(java.security.Permission) checkPermission}
1553 * method is invoked with a {@link RuntimePermission RuntimePermission}{@code
1554 * ("setContextClassLoader")} permission to see if setting the context
1555 * ClassLoader is permitted.
1556 *
1557 * @param cl
1558 * the context ClassLoader for this Thread, or null indicating the
1559 * system class loader (or, failing that, the bootstrap class loader)
1560 *
1561 * @throws SecurityException
1562 * if the current thread cannot set the context ClassLoader
1563 *
1564 * @since 1.2
1565 */
1566 public void setContextClassLoader(ClassLoader cl) {
1567 SecurityManager sm = System.getSecurityManager();
1568 if (sm != null) {
1569 sm.checkPermission(new RuntimePermission("setContextClassLoader"));
1570 }
1571 contextClassLoader = cl;
1572 }
1573
1574 /**
1575 * Returns {@code true} if and only if the current thread holds the
1576 * monitor lock on the specified object.
1577 *
1578 * <p>This method is designed to allow a program to assert that
1579 * the current thread already holds a specified lock:
1580 * <pre>
1581 * assert Thread.holdsLock(obj);
1582 * </pre>
1583 *
1584 * @param obj the object on which to test lock ownership
1585 * @throws NullPointerException if obj is {@code null}
1586 * @return {@code true} if the current thread holds the monitor lock on
1587 * the specified object.
1588 * @since 1.4
1589 */
1590 public static native boolean holdsLock(Object obj);
1591
1592 private static final StackTraceElement[] EMPTY_STACK_TRACE
1593 = new StackTraceElement[0];
1594
1595 /**
1596 * Returns an array of stack trace elements representing the stack dump
1597 * of this thread. This method will return a zero-length array if
1598 * this thread has not started, has started but has not yet been
1599 * scheduled to run by the system, or has terminated.
1600 * If the returned array is of non-zero length then the first element of
1601 * the array represents the top of the stack, which is the most recent
1602 * method invocation in the sequence. The last element of the array
1603 * represents the bottom of the stack, which is the least recent method
1604 * invocation in the sequence.
1605 *
1606 * <p>If there is a security manager, and this thread is not
1607 * the current thread, then the security manager's
1608 * {@code checkPermission} method is called with a
1609 * {@code RuntimePermission("getStackTrace")} permission
1610 * to see if it's ok to get the stack trace.
1611 *
1612 * <p>Some virtual machines may, under some circumstances, omit one
1613 * or more stack frames from the stack trace. In the extreme case,
1614 * a virtual machine that has no stack trace information concerning
1615 * this thread is permitted to return a zero-length array from this
1616 * method.
1617 *
1618 * @return an array of {@code StackTraceElement},
1619 * each represents one stack frame.
1620 *
1621 * @throws SecurityException
1622 * if a security manager exists and its
1623 * {@code checkPermission} method doesn't allow
1624 * getting the stack trace of thread.
1625 * @see SecurityManager#checkPermission
1626 * @see RuntimePermission
1627 * @see Throwable#getStackTrace
1628 *
1629 * @since 1.5
1630 */
1631 public StackTraceElement[] getStackTrace() {
1632 if (this != Thread.currentThread()) {
1633 // check for getStackTrace permission
1634 SecurityManager security = System.getSecurityManager();
1635 if (security != null) {
1636 security.checkPermission(
1637 SecurityConstants.GET_STACK_TRACE_PERMISSION);
1638 }
1639 // optimization so we do not call into the vm for threads that
1640 // have not yet started or have terminated
1641 if (!isAlive()) {
1642 return EMPTY_STACK_TRACE;
1643 }
1644 StackTraceElement[][] stackTraceArray = dumpThreads(new Thread[] {this});
1645 StackTraceElement[] stackTrace = stackTraceArray[0];
1646 // a thread that was alive during the previous isAlive call may have
1647 // since terminated, therefore not having a stacktrace.
1648 if (stackTrace == null) {
1649 stackTrace = EMPTY_STACK_TRACE;
1650 }
1651 return stackTrace;
1652 } else {
1653 return (new Exception()).getStackTrace();
1654 }
1655 }
1656
1657 /**
1658 * Returns a map of stack traces for all live threads.
1659 * The map keys are threads and each map value is an array of
1660 * {@code StackTraceElement} that represents the stack dump
1661 * of the corresponding {@code Thread}.
1662 * The returned stack traces are in the format specified for
1663 * the {@link #getStackTrace getStackTrace} method.
1664 *
1665 * <p>The threads may be executing while this method is called.
1666 * The stack trace of each thread only represents a snapshot and
1667 * each stack trace may be obtained at different time. A zero-length
1668 * array will be returned in the map value if the virtual machine has
1669 * no stack trace information about a thread.
1670 *
1671 * <p>If there is a security manager, then the security manager's
1672 * {@code checkPermission} method is called with a
1673 * {@code RuntimePermission("getStackTrace")} permission as well as
1674 * {@code RuntimePermission("modifyThreadGroup")} permission
1675 * to see if it is ok to get the stack trace of all threads.
1676 *
1677 * @return a {@code Map} from {@code Thread} to an array of
1678 * {@code StackTraceElement} that represents the stack trace of
1679 * the corresponding thread.
1680 *
1681 * @throws SecurityException
1682 * if a security manager exists and its
1683 * {@code checkPermission} method doesn't allow
1684 * getting the stack trace of thread.
1685 * @see #getStackTrace
1686 * @see SecurityManager#checkPermission
1687 * @see RuntimePermission
1688 * @see Throwable#getStackTrace
1689 *
1690 * @since 1.5
1691 */
1692 public static Map<Thread, StackTraceElement[]> getAllStackTraces() {
1693 // check for getStackTrace permission
1694 SecurityManager security = System.getSecurityManager();
1695 if (security != null) {
1696 security.checkPermission(
1697 SecurityConstants.GET_STACK_TRACE_PERMISSION);
1698 security.checkPermission(
1699 SecurityConstants.MODIFY_THREADGROUP_PERMISSION);
1700 }
1701
1702 // Get a snapshot of the list of all threads
1703 Thread[] threads = getThreads();
1704 StackTraceElement[][] traces = dumpThreads(threads);
1705 Map<Thread, StackTraceElement[]> m = new HashMap<>(threads.length);
1706 for (int i = 0; i < threads.length; i++) {
1707 StackTraceElement[] stackTrace = traces[i];
1708 if (stackTrace != null) {
1709 m.put(threads[i], stackTrace);
1710 }
1711 // else terminated so we don't put it in the map
1712 }
1713 return m;
1714 }
1715
1716
1717 private static final RuntimePermission SUBCLASS_IMPLEMENTATION_PERMISSION =
1718 new RuntimePermission("enableContextClassLoaderOverride");
1719
1720 /** cache of subclass security audit results */
1721 /* Replace with ConcurrentReferenceHashMap when/if it appears in a future
1722 * release */
1723 private static class Caches {
1724 /** cache of subclass security audit results */
1725 static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits =
1726 new ConcurrentHashMap<>();
1727
1728 /** queue for WeakReferences to audited subclasses */
1729 static final ReferenceQueue<Class<?>> subclassAuditsQueue =
1730 new ReferenceQueue<>();
1731 }
1732
1733 /**
1734 * Verifies that this (possibly subclass) instance can be constructed
1735 * without violating security constraints: the subclass must not override
1736 * security-sensitive non-final methods, or else the
1737 * "enableContextClassLoaderOverride" RuntimePermission is checked.
1738 */
1739 private static boolean isCCLOverridden(Class<?> cl) {
1740 if (cl == Thread.class)
1741 return false;
1742
1743 processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits);
1744 WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue);
1745 Boolean result = Caches.subclassAudits.get(key);
1746 if (result == null) {
1747 result = Boolean.valueOf(auditSubclass(cl));
1748 Caches.subclassAudits.putIfAbsent(key, result);
1749 }
1750
1751 return result.booleanValue();
1752 }
1753
1754 /**
1755 * Performs reflective checks on given subclass to verify that it doesn't
1756 * override security-sensitive non-final methods. Returns true if the
1757 * subclass overrides any of the methods, false otherwise.
1758 */
1759 private static boolean auditSubclass(final Class<?> subcl) {
1760 Boolean result = AccessController.doPrivileged(
1761 new PrivilegedAction<>() {
1762 public Boolean run() {
1763 for (Class<?> cl = subcl;
1764 cl != Thread.class;
1765 cl = cl.getSuperclass())
1766 {
1767 try {
1768 cl.getDeclaredMethod("getContextClassLoader", new Class<?>[0]);
1769 return Boolean.TRUE;
1770 } catch (NoSuchMethodException ex) {
1771 }
1772 try {
1773 Class<?>[] params = {ClassLoader.class};
1774 cl.getDeclaredMethod("setContextClassLoader", params);
1775 return Boolean.TRUE;
1776 } catch (NoSuchMethodException ex) {
1777 }
1778 }
1779 return Boolean.FALSE;
1780 }
1781 }
1782 );
1783 return result.booleanValue();
1784 }
1785
1786 private static native StackTraceElement[][] dumpThreads(Thread[] threads);
1787 private static native Thread[] getThreads();
1788
1789 /**
1790 * Returns the identifier of this Thread. The thread ID is a positive
1791 * {@code long} number generated when this thread was created.
1792 * The thread ID is unique and remains unchanged during its lifetime.
1793 * When a thread is terminated, this thread ID may be reused.
1794 *
1795 * @return this thread's ID.
1796 * @since 1.5
1797 */
1798 public long getId() {
1799 return tid;
1800 }
1801
1802 /**
1803 * A thread state. A thread can be in one of the following states:
1804 * <ul>
1805 * <li>{@link #NEW}<br>
1806 * A thread that has not yet started is in this state.
1807 * </li>
1808 * <li>{@link #RUNNABLE}<br>
1809 * A thread executing in the Java virtual machine is in this state.
1810 * </li>
1811 * <li>{@link #BLOCKED}<br>
1812 * A thread that is blocked waiting for a monitor lock
1813 * is in this state.
1814 * </li>
1815 * <li>{@link #WAITING}<br>
1816 * A thread that is waiting indefinitely for another thread to
1817 * perform a particular action is in this state.
1818 * </li>
1819 * <li>{@link #TIMED_WAITING}<br>
1820 * A thread that is waiting for another thread to perform an action
1821 * for up to a specified waiting time is in this state.
1822 * </li>
1823 * <li>{@link #TERMINATED}<br>
1824 * A thread that has exited is in this state.
1825 * </li>
1826 * </ul>
1827 *
1828 * <p>
1829 * A thread can be in only one state at a given point in time.
1830 * These states are virtual machine states which do not reflect
1831 * any operating system thread states.
1832 *
1833 * @since 1.5
1834 * @see #getState
1835 */
1836 public enum State {
1837 /**
1838 * Thread state for a thread which has not yet started.
1839 */
1840 NEW,
1841
1842 /**
1843 * Thread state for a runnable thread. A thread in the runnable
1844 * state is executing in the Java virtual machine but it may
1845 * be waiting for other resources from the operating system
1846 * such as processor.
1847 */
1848 RUNNABLE,
1849
1850 /**
1851 * Thread state for a thread blocked waiting for a monitor lock.
1852 * A thread in the blocked state is waiting for a monitor lock
1853 * to enter a synchronized block/method or
1854 * reenter a synchronized block/method after calling
1855 * {@link Object#wait() Object.wait}.
1856 */
1857 BLOCKED,
1858
1859 /**
1860 * Thread state for a waiting thread.
1861 * A thread is in the waiting state due to calling one of the
1862 * following methods:
1863 * <ul>
1864 * <li>{@link Object#wait() Object.wait} with no timeout</li>
1865 * <li>{@link #join() Thread.join} with no timeout</li>
1866 * <li>{@link LockSupport#park() LockSupport.park}</li>
1867 * </ul>
1868 *
1869 * <p>A thread in the waiting state is waiting for another thread to
1870 * perform a particular action.
1871 *
1872 * For example, a thread that has called {@code Object.wait()}
1873 * on an object is waiting for another thread to call
1874 * {@code Object.notify()} or {@code Object.notifyAll()} on
1875 * that object. A thread that has called {@code Thread.join()}
1876 * is waiting for a specified thread to terminate.
1877 */
1878 WAITING,
1879
1880 /**
1881 * Thread state for a waiting thread with a specified waiting time.
1882 * A thread is in the timed waiting state due to calling one of
1883 * the following methods with a specified positive waiting time:
1884 * <ul>
1885 * <li>{@link #sleep Thread.sleep}</li>
1886 * <li>{@link Object#wait(long) Object.wait} with timeout</li>
1887 * <li>{@link #join(long) Thread.join} with timeout</li>
1888 * <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
1889 * <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
1890 * </ul>
1891 */
1892 TIMED_WAITING,
1893
1894 /**
1895 * Thread state for a terminated thread.
1896 * The thread has completed execution.
1897 */
1898 TERMINATED;
1899 }
1900
1901 /**
1902 * Returns the state of this thread.
1903 * This method is designed for use in monitoring of the system state,
1904 * not for synchronization control.
1905 *
1906 * @return this thread's state.
1907 * @since 1.5
1908 */
1909 public State getState() {
1910 // get current thread state
1911 return jdk.internal.misc.VM.toThreadState(threadStatus);
1912 }
1913
1914 // Added in JSR-166
1915
1916 /**
1917 * Interface for handlers invoked when a {@code Thread} abruptly
1918 * terminates due to an uncaught exception.
1919 * <p>When a thread is about to terminate due to an uncaught exception
1920 * the Java Virtual Machine will query the thread for its
1921 * {@code UncaughtExceptionHandler} using
1922 * {@link #getUncaughtExceptionHandler} and will invoke the handler's
1923 * {@code uncaughtException} method, passing the thread and the
1924 * exception as arguments.
1925 * If a thread has not had its {@code UncaughtExceptionHandler}
1926 * explicitly set, then its {@code ThreadGroup} object acts as its
1927 * {@code UncaughtExceptionHandler}. If the {@code ThreadGroup} object
1928 * has no
1929 * special requirements for dealing with the exception, it can forward
1930 * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler
1931 * default uncaught exception handler}.
1932 *
1933 * @see #setDefaultUncaughtExceptionHandler
1934 * @see #setUncaughtExceptionHandler
1935 * @see ThreadGroup#uncaughtException
1936 * @since 1.5
1937 */
1938 @FunctionalInterface
1939 public interface UncaughtExceptionHandler {
1940 /**
1941 * Method invoked when the given thread terminates due to the
1942 * given uncaught exception.
1943 * <p>Any exception thrown by this method will be ignored by the
1944 * Java Virtual Machine.
1945 * @param t the thread
1946 * @param e the exception
1947 */
1948 void uncaughtException(Thread t, Throwable e);
1949 }
1950
1951 // null unless explicitly set
1952 private volatile UncaughtExceptionHandler uncaughtExceptionHandler;
1953
1954 // null unless explicitly set
1955 private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler;
1956
1957 /**
1958 * Set the default handler invoked when a thread abruptly terminates
1959 * due to an uncaught exception, and no other handler has been defined
1960 * for that thread.
1961 *
1962 * <p>Uncaught exception handling is controlled first by the thread, then
1963 * by the thread's {@link ThreadGroup} object and finally by the default
1964 * uncaught exception handler. If the thread does not have an explicit
1965 * uncaught exception handler set, and the thread's thread group
1966 * (including parent thread groups) does not specialize its
1967 * {@code uncaughtException} method, then the default handler's
1968 * {@code uncaughtException} method will be invoked.
1969 * <p>By setting the default uncaught exception handler, an application
1970 * can change the way in which uncaught exceptions are handled (such as
1971 * logging to a specific device, or file) for those threads that would
1972 * already accept whatever "default" behavior the system
1973 * provided.
1974 *
1975 * <p>Note that the default uncaught exception handler should not usually
1976 * defer to the thread's {@code ThreadGroup} object, as that could cause
1977 * infinite recursion.
1978 *
1979 * @param eh the object to use as the default uncaught exception handler.
1980 * If {@code null} then there is no default handler.
1981 *
1982 * @throws SecurityException if a security manager is present and it denies
1983 * {@link RuntimePermission}{@code ("setDefaultUncaughtExceptionHandler")}
1984 *
1985 * @see #setUncaughtExceptionHandler
1986 * @see #getUncaughtExceptionHandler
1987 * @see ThreadGroup#uncaughtException
1988 * @since 1.5
1989 */
1990 public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
1991 SecurityManager sm = System.getSecurityManager();
1992 if (sm != null) {
1993 sm.checkPermission(
1994 new RuntimePermission("setDefaultUncaughtExceptionHandler")
1995 );
1996 }
1997
1998 defaultUncaughtExceptionHandler = eh;
1999 }
2000
2001 /**
2002 * Returns the default handler invoked when a thread abruptly terminates
2003 * due to an uncaught exception. If the returned value is {@code null},
2004 * there is no default.
2005 * @since 1.5
2006 * @see #setDefaultUncaughtExceptionHandler
2007 * @return the default uncaught exception handler for all threads
2008 */
2009 public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler(){
2010 return defaultUncaughtExceptionHandler;
2011 }
2012
2013 /**
2014 * Returns the handler invoked when this thread abruptly terminates
2015 * due to an uncaught exception. If this thread has not had an
2016 * uncaught exception handler explicitly set then this thread's
2017 * {@code ThreadGroup} object is returned, unless this thread
2018 * has terminated, in which case {@code null} is returned.
2019 * @since 1.5
2020 * @return the uncaught exception handler for this thread
2021 */
2022 public UncaughtExceptionHandler getUncaughtExceptionHandler() {
2023 return uncaughtExceptionHandler != null ?
2024 uncaughtExceptionHandler : group;
2025 }
2026
2027 /**
2028 * Set the handler invoked when this thread abruptly terminates
2029 * due to an uncaught exception.
2030 * <p>A thread can take full control of how it responds to uncaught
2031 * exceptions by having its uncaught exception handler explicitly set.
2032 * If no such handler is set then the thread's {@code ThreadGroup}
2033 * object acts as its handler.
2034 * @param eh the object to use as this thread's uncaught exception
2035 * handler. If {@code null} then this thread has no explicit handler.
2036 * @throws SecurityException if the current thread is not allowed to
2037 * modify this thread.
2038 * @see #setDefaultUncaughtExceptionHandler
2039 * @see ThreadGroup#uncaughtException
2040 * @since 1.5
2041 */
2042 public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
2043 checkAccess();
2044 uncaughtExceptionHandler = eh;
2045 }
2046
2047 /**
2048 * Dispatch an uncaught exception to the handler. This method is
2049 * intended to be called only by the JVM.
2050 */
2051 private void dispatchUncaughtException(Throwable e) {
2052 getUncaughtExceptionHandler().uncaughtException(this, e);
2053 }
2054
2055 /**
2056 * Removes from the specified map any keys that have been enqueued
2057 * on the specified reference queue.
2058 */
2059 static void processQueue(ReferenceQueue<Class<?>> queue,
2060 ConcurrentMap<? extends
2061 WeakReference<Class<?>>, ?> map)
2062 {
2063 Reference<? extends Class<?>> ref;
2064 while((ref = queue.poll()) != null) {
2065 map.remove(ref);
2066 }
2067 }
2068
2069 /**
2070 * Weak key for Class objects.
2071 **/
2072 static class WeakClassKey extends WeakReference<Class<?>> {
2073 /**
2074 * saved value of the referent's identity hash code, to maintain
2075 * a consistent hash code after the referent has been cleared
2076 */
2077 private final int hash;
2078
2079 /**
2080 * Create a new WeakClassKey to the given object, registered
2081 * with a queue.
2082 */
2083 WeakClassKey(Class<?> cl, ReferenceQueue<Class<?>> refQueue) {
2084 super(cl, refQueue);
2085 hash = System.identityHashCode(cl);
2086 }
2087
2088 /**
2089 * Returns the identity hash code of the original referent.
2090 */
2091 @Override
2092 public int hashCode() {
2093 return hash;
2094 }
2095
2096 /**
2097 * Returns true if the given object is this identical
2098 * WeakClassKey instance, or, if this object's referent has not
2099 * been cleared, if the given object is another WeakClassKey
2100 * instance with the identical non-null referent as this one.
2101 */
2102 @Override
2103 public boolean equals(Object obj) {
2104 if (obj == this)
2105 return true;
2106
2107 if (obj instanceof WeakClassKey) {
2108 Object referent = get();
2109 return (referent != null) &&
2110 (referent == ((WeakClassKey) obj).get());
2111 } else {
2112 return false;
2113 }
2114 }
2115 }
2116
2117
2118 // The following three initially uninitialized fields are exclusively
2119 // managed by class java.util.concurrent.ThreadLocalRandom. These
2120 // fields are used to build the high-performance PRNGs in the
2121 // concurrent code, and we can not risk accidental false sharing.
2122 // Hence, the fields are isolated with @Contended.
2123
2124 /** The current seed for a ThreadLocalRandom */
2125 @jdk.internal.vm.annotation.Contended("tlr")
2126 long threadLocalRandomSeed;
2127
2128 /** Probe hash value; nonzero if threadLocalRandomSeed initialized */
2129 @jdk.internal.vm.annotation.Contended("tlr")
2130 int threadLocalRandomProbe;
2131
2132 /** Secondary seed isolated from public ThreadLocalRandom sequence */
2133 @jdk.internal.vm.annotation.Contended("tlr")
2134 int threadLocalRandomSecondarySeed;
2135
2136 /* Some private helper methods */
2137 private native void setPriority0(int newPriority);
2138 private native void stop0(Object o);
2139 private native void suspend0();
2140 private native void resume0();
2141 private native void interrupt0();
2142 private native void setNativeName(String name);
2143 }