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
151 /* Whether or not the thread is a daemon thread. */
152 private boolean daemon = false;
153
154 /* Fields reserved for exclusive use by the JVM */
155 private boolean stillborn = false;
156 private long eetop;
157
158 /* What will be run. */
159 private Runnable target;
160
161 /* The group of this thread */
162 private ThreadGroup group;
163
164 /* The context ClassLoader for this thread */
165 private ClassLoader contextClassLoader;
166
167 /* The inherited AccessControlContext of this thread */
168 private AccessControlContext inheritedAccessControlContext;
169
170 /* For autonumbering anonymous threads. */
171 private static int threadInitNumber;
172 private static synchronized int nextThreadNum() {
173 return threadInitNumber++;
174 }
175
176 /* ThreadLocal values pertaining to this thread. This map is maintained
177 * by the ThreadLocal class. */
178 ThreadLocal.ThreadLocalMap threadLocals = null;
179
180 /*
181 * InheritableThreadLocal values pertaining to this thread. This map is
182 * maintained by the InheritableThreadLocal class.
183 */
184 ThreadLocal.ThreadLocalMap inheritableThreadLocals = null;
185
186 /*
187 * The requested stack size for this thread, or 0 if the creator did
188 * not specify a stack size. It is up to the VM to do whatever it
189 * likes with this number; some VMs will ignore it.
190 */
191 private final long stackSize;
192
193 /*
194 * JVM-private state that persists after native thread termination.
195 */
196 private long nativeParkEventPointer;
197
198 /*
199 * Thread ID
200 */
201 private final long tid;
202
203 /* For generating thread ID */
204 private static long threadSeqNumber;
205
206 private static synchronized long nextThreadID() {
207 return ++threadSeqNumber;
208 }
209
210 /*
211 * Java thread status for tools, default indicates thread 'not yet started'
212 */
213 private volatile int threadStatus;
214
215 /**
216 * The argument supplied to the current call to
217 * java.util.concurrent.locks.LockSupport.park.
218 * Set by (private) java.util.concurrent.locks.LockSupport.setBlocker
219 * Accessed using java.util.concurrent.locks.LockSupport.getBlocker
220 */
221 volatile Object parkBlocker;
222
223 /* The object in which this thread is blocked in an interruptible I/O
224 * operation, if any. The blocker's interrupt method should be invoked
225 * after setting this thread's interrupt status.
226 */
227 private volatile Interruptible blocker;
228 private final Object blockerLock = new Object();
229
230 /* Set the blocker field; invoked via jdk.internal.misc.SharedSecrets
231 * from java.nio code
232 */
233 static void blockedOn(Interruptible b) {
234 Thread me = Thread.currentThread();
235 synchronized (me.blockerLock) {
236 me.blocker = b;
237 }
238 }
239
240 /**
241 * The minimum priority that a thread can have.
242 */
243 public static final int MIN_PRIORITY = 1;
244
245 /**
246 * The default priority that is assigned to a thread.
247 */
248 public static final int NORM_PRIORITY = 5;
249
250 /**
251 * The maximum priority that a thread can have.
252 */
253 public static final int MAX_PRIORITY = 10;
254
255 /**
256 * Returns a reference to the currently executing thread object.
257 *
258 * @return the currently executing thread.
259 */
260 @HotSpotIntrinsicCandidate
261 public static native Thread currentThread();
262
263 /**
264 * A hint to the scheduler that the current thread is willing to yield
265 * its current use of a processor. The scheduler is free to ignore this
266 * hint.
267 *
268 * <p> Yield is a heuristic attempt to improve relative progression
269 * between threads that would otherwise over-utilise a CPU. Its use
270 * should be combined with detailed profiling and benchmarking to
271 * ensure that it actually has the desired effect.
272 *
273 * <p> It is rarely appropriate to use this method. It may be useful
274 * for debugging or testing purposes, where it may help to reproduce
275 * bugs due to race conditions. It may also be useful when designing
276 * concurrency control constructs such as the ones in the
277 * {@link java.util.concurrent.locks} package.
278 */
279 public static native void yield();
280
281 /**
282 * Causes the currently executing thread to sleep (temporarily cease
283 * execution) for the specified number of milliseconds, subject to
284 * the precision and accuracy of system timers and schedulers. The thread
285 * does not lose ownership of any monitors.
286 *
287 * @param millis
288 * the length of time to sleep in milliseconds
289 *
290 * @throws IllegalArgumentException
291 * if the value of {@code millis} is negative
292 *
293 * @throws InterruptedException
294 * if any thread has interrupted the current thread. The
295 * <i>interrupted status</i> of the current thread is
296 * cleared when this exception is thrown.
297 */
298 public static native void sleep(long millis) throws InterruptedException;
299
300 /**
301 * Causes the currently executing thread to sleep (temporarily cease
302 * execution) for the specified number of milliseconds plus the specified
303 * number of nanoseconds, subject to the precision and accuracy of system
304 * timers and schedulers. The thread does not lose ownership of any
305 * monitors.
306 *
307 * @param millis
308 * the length of time to sleep in milliseconds
309 *
310 * @param nanos
311 * {@code 0-999999} additional nanoseconds to sleep
312 *
313 * @throws IllegalArgumentException
314 * if the value of {@code millis} is negative, or the value of
315 * {@code nanos} is not in the range {@code 0-999999}
316 *
317 * @throws InterruptedException
318 * if any thread has interrupted the current thread. The
319 * <i>interrupted status</i> of the current thread is
320 * cleared when this exception is thrown.
321 */
322 public static void sleep(long millis, int nanos)
323 throws InterruptedException {
324 if (millis < 0) {
325 throw new IllegalArgumentException("timeout value is negative");
326 }
327
328 if (nanos < 0 || nanos > 999999) {
329 throw new IllegalArgumentException(
330 "nanosecond timeout value out of range");
331 }
332
333 if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
334 millis++;
335 }
336
337 sleep(millis);
338 }
339
340 /**
341 * Indicates that the caller is momentarily unable to progress, until the
342 * occurrence of one or more actions on the part of other activities. By
343 * invoking this method within each iteration of a spin-wait loop construct,
344 * the calling thread indicates to the runtime that it is busy-waiting.
345 * The runtime may take action to improve the performance of invoking
346 * spin-wait loop constructions.
347 *
348 * @apiNote
349 * As an example consider a method in a class that spins in a loop until
350 * some flag is set outside of that method. A call to the {@code onSpinWait}
351 * method should be placed inside the spin loop.
352 * <pre>{@code
353 * class EventHandler {
354 * volatile boolean eventNotificationNotReceived;
355 * void waitForEventAndHandleIt() {
356 * while ( eventNotificationNotReceived ) {
357 * java.lang.Thread.onSpinWait();
358 * }
359 * readAndProcessEvent();
360 * }
361 *
362 * void readAndProcessEvent() {
363 * // Read event from some source and process it
364 * . . .
365 * }
366 * }
367 * }</pre>
368 * <p>
369 * The code above would remain correct even if the {@code onSpinWait}
370 * method was not called at all. However on some architectures the Java
371 * Virtual Machine may issue the processor instructions to address such
372 * code patterns in a more beneficial way.
373 *
374 * @since 9
375 */
376 @HotSpotIntrinsicCandidate
377 public static void onSpinWait() {}
378
379 /**
380 * Initializes a Thread.
381 *
382 * @param g the Thread group
383 * @param target the object whose run() method gets called
384 * @param name the name of the new Thread
385 * @param stackSize the desired stack size for the new thread, or
386 * zero to indicate that this parameter is to be ignored.
387 * @param acc the AccessControlContext to inherit, or
388 * AccessController.getContext() if null
389 * @param inheritThreadLocals if {@code true}, inherit initial values for
390 * inheritable thread-locals from the constructing thread
391 */
392 private Thread(ThreadGroup g, Runnable target, String name,
393 long stackSize, AccessControlContext acc,
394 boolean inheritThreadLocals) {
395 if (name == null) {
396 throw new NullPointerException("name cannot be null");
397 }
398
399 this.name = name;
400
401 Thread parent = currentThread();
402 SecurityManager security = System.getSecurityManager();
403 if (g == null) {
404 /* Determine if it's an applet or not */
405
406 /* If there is a security manager, ask the security manager
407 what to do. */
408 if (security != null) {
409 g = security.getThreadGroup();
410 }
411
412 /* If the security manager doesn't have a strong opinion
413 on the matter, use the parent thread group. */
414 if (g == null) {
415 g = parent.getThreadGroup();
416 }
417 }
418
419 /* checkAccess regardless of whether or not threadgroup is
420 explicitly passed in. */
421 g.checkAccess();
422
423 /*
424 * Do we have the required permissions?
425 */
426 if (security != null) {
427 if (isCCLOverridden(getClass())) {
428 security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
429 }
430 }
431
432 g.addUnstarted();
433
434 this.group = g;
435 this.daemon = parent.isDaemon();
436 this.priority = parent.getPriority();
437 if (security == null || isCCLOverridden(parent.getClass()))
438 this.contextClassLoader = parent.getContextClassLoader();
439 else
440 this.contextClassLoader = parent.contextClassLoader;
441 this.inheritedAccessControlContext =
442 acc != null ? acc : AccessController.getContext();
443 this.target = target;
444 setPriority(priority);
445 if (inheritThreadLocals && parent.inheritableThreadLocals != null)
446 this.inheritableThreadLocals =
447 ThreadLocal.createInheritedMap(parent.inheritableThreadLocals);
448 /* Stash the specified stack size in case the VM cares */
449 this.stackSize = stackSize;
450
451 /* Set thread ID */
452 this.tid = nextThreadID();
453 }
454
455 /**
456 * Throws CloneNotSupportedException as a Thread can not be meaningfully
457 * cloned. Construct a new Thread instead.
458 *
459 * @throws CloneNotSupportedException
460 * always
461 */
462 @Override
463 protected Object clone() throws CloneNotSupportedException {
464 throw new CloneNotSupportedException();
465 }
466
467 /**
468 * Allocates a new {@code Thread} object. This constructor has the same
469 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
470 * {@code (null, null, gname)}, where {@code gname} is a newly generated
471 * name. Automatically generated names are of the form
472 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
473 */
474 public Thread() {
475 this(null, null, "Thread-" + nextThreadNum(), 0);
476 }
477
478 /**
479 * Allocates a new {@code Thread} object. This constructor has the same
480 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
481 * {@code (null, target, gname)}, where {@code gname} is a newly generated
482 * name. Automatically generated names are of the form
483 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
484 *
485 * @param target
486 * the object whose {@code run} method is invoked when this thread
487 * is started. If {@code null}, this classes {@code run} method does
488 * nothing.
489 */
490 public Thread(Runnable target) {
491 this(null, target, "Thread-" + nextThreadNum(), 0);
492 }
493
494 /**
495 * Creates a new Thread that inherits the given AccessControlContext
496 * but thread-local variables are not inherited.
497 * This is not a public constructor.
498 */
499 Thread(Runnable target, AccessControlContext acc) {
500 this(null, target, "Thread-" + nextThreadNum(), 0, acc, false);
501 }
502
503 /**
504 * Allocates a new {@code Thread} object. This constructor has the same
505 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
506 * {@code (group, target, gname)} ,where {@code gname} is a newly generated
507 * name. Automatically generated names are of the form
508 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
509 *
510 * @param group
511 * the thread group. If {@code null} and there is a security
512 * manager, the group is determined by {@linkplain
513 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
514 * If there is not a security manager or {@code
515 * SecurityManager.getThreadGroup()} returns {@code null}, the group
516 * is set to the current thread's thread group.
517 *
518 * @param target
519 * the object whose {@code run} method is invoked when this thread
520 * is started. If {@code null}, this thread's run method is invoked.
521 *
522 * @throws SecurityException
523 * if the current thread cannot create a thread in the specified
524 * thread group
525 */
526 public Thread(ThreadGroup group, Runnable target) {
527 this(group, target, "Thread-" + nextThreadNum(), 0);
528 }
529
530 /**
531 * Allocates a new {@code Thread} object. This constructor has the same
532 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
533 * {@code (null, null, name)}.
534 *
535 * @param name
536 * the name of the new thread
537 */
538 public Thread(String name) {
539 this(null, null, name, 0);
540 }
541
542 /**
543 * Allocates a new {@code Thread} object. This constructor has the same
544 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
545 * {@code (group, null, name)}.
546 *
547 * @param group
548 * the thread group. If {@code null} and there is a security
549 * manager, the group is determined by {@linkplain
550 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
551 * If there is not a security manager or {@code
552 * SecurityManager.getThreadGroup()} returns {@code null}, the group
553 * is set to the current thread's thread group.
554 *
555 * @param name
556 * the name of the new thread
557 *
558 * @throws SecurityException
559 * if the current thread cannot create a thread in the specified
560 * thread group
561 */
562 public Thread(ThreadGroup group, String name) {
563 this(group, null, name, 0);
564 }
565
566 /**
567 * Allocates a new {@code Thread} object. This constructor has the same
568 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
569 * {@code (null, target, name)}.
570 *
571 * @param target
572 * the object whose {@code run} method is invoked when this thread
573 * is started. If {@code null}, this thread's run method is invoked.
574 *
575 * @param name
576 * the name of the new thread
577 */
578 public Thread(Runnable target, String name) {
579 this(null, target, name, 0);
580 }
581
582 /**
583 * Allocates a new {@code Thread} object so that it has {@code target}
584 * as its run object, has the specified {@code name} as its name,
585 * and belongs to the thread group referred to by {@code group}.
586 *
587 * <p>If there is a security manager, its
588 * {@link SecurityManager#checkAccess(ThreadGroup) checkAccess}
589 * method is invoked with the ThreadGroup as its argument.
590 *
591 * <p>In addition, its {@code checkPermission} method is invoked with
592 * the {@code RuntimePermission("enableContextClassLoaderOverride")}
593 * permission when invoked directly or indirectly by the constructor
594 * of a subclass which overrides the {@code getContextClassLoader}
595 * or {@code setContextClassLoader} methods.
596 *
597 * <p>The priority of the newly created thread is set equal to the
598 * priority of the thread creating it, that is, the currently running
599 * thread. The method {@linkplain #setPriority setPriority} may be
600 * used to change the priority to a new value.
601 *
602 * <p>The newly created thread is initially marked as being a daemon
603 * thread if and only if the thread creating it is currently marked
604 * as a daemon thread. The method {@linkplain #setDaemon setDaemon}
605 * may be used to change whether or not a thread is a daemon.
606 *
607 * @param group
608 * the thread group. If {@code null} and there is a security
609 * manager, the group is determined by {@linkplain
610 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
611 * If there is not a security manager or {@code
612 * SecurityManager.getThreadGroup()} returns {@code null}, the group
613 * is set to the current thread's thread group.
614 *
615 * @param target
616 * the object whose {@code run} method is invoked when this thread
617 * is started. If {@code null}, this thread's run method is invoked.
618 *
619 * @param name
620 * the name of the new thread
621 *
622 * @throws SecurityException
623 * if the current thread cannot create a thread in the specified
624 * thread group or cannot override the context class loader methods.
625 */
626 public Thread(ThreadGroup group, Runnable target, String name) {
627 this(group, target, name, 0);
628 }
629
630 /**
631 * Allocates a new {@code Thread} object so that it has {@code target}
632 * as its run object, has the specified {@code name} as its name,
633 * and belongs to the thread group referred to by {@code group}, and has
634 * the specified <i>stack size</i>.
635 *
636 * <p>This constructor is identical to {@link
637 * #Thread(ThreadGroup,Runnable,String)} with the exception of the fact
638 * that it allows the thread stack size to be specified. The stack size
639 * is the approximate number of bytes of address space that the virtual
640 * machine is to allocate for this thread's stack. <b>The effect of the
641 * {@code stackSize} parameter, if any, is highly platform dependent.</b>
642 *
643 * <p>On some platforms, specifying a higher value for the
644 * {@code stackSize} parameter may allow a thread to achieve greater
645 * recursion depth before throwing a {@link StackOverflowError}.
646 * Similarly, specifying a lower value may allow a greater number of
647 * threads to exist concurrently without throwing an {@link
648 * OutOfMemoryError} (or other internal error). The details of
649 * the relationship between the value of the {@code stackSize} parameter
650 * and the maximum recursion depth and concurrency level are
651 * platform-dependent. <b>On some platforms, the value of the
652 * {@code stackSize} parameter may have no effect whatsoever.</b>
653 *
654 * <p>The virtual machine is free to treat the {@code stackSize}
655 * parameter as a suggestion. If the specified value is unreasonably low
656 * for the platform, the virtual machine may instead use some
657 * platform-specific minimum value; if the specified value is unreasonably
658 * high, the virtual machine may instead use some platform-specific
659 * maximum. Likewise, the virtual machine is free to round the specified
660 * value up or down as it sees fit (or to ignore it completely).
661 *
662 * <p>Specifying a value of zero for the {@code stackSize} parameter will
663 * cause this constructor to behave exactly like the
664 * {@code Thread(ThreadGroup, Runnable, String)} constructor.
665 *
666 * <p><i>Due to the platform-dependent nature of the behavior of this
667 * constructor, extreme care should be exercised in its use.
668 * The thread stack size necessary to perform a given computation will
669 * likely vary from one JRE implementation to another. In light of this
670 * variation, careful tuning of the stack size parameter may be required,
671 * and the tuning may need to be repeated for each JRE implementation on
672 * which an application is to run.</i>
673 *
674 * <p>Implementation note: Java platform implementers are encouraged to
675 * document their implementation's behavior with respect to the
676 * {@code stackSize} parameter.
677 *
678 *
679 * @param group
680 * the thread group. If {@code null} and there is a security
681 * manager, the group is determined by {@linkplain
682 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
683 * If there is not a security manager or {@code
684 * SecurityManager.getThreadGroup()} returns {@code null}, the group
685 * is set to the current thread's thread group.
686 *
687 * @param target
688 * the object whose {@code run} method is invoked when this thread
689 * is started. If {@code null}, this thread's run method is invoked.
690 *
691 * @param name
692 * the name of the new thread
693 *
694 * @param stackSize
695 * the desired stack size for the new thread, or zero to indicate
696 * that this parameter is to be ignored.
697 *
698 * @throws SecurityException
699 * if the current thread cannot create a thread in the specified
700 * thread group
701 *
702 * @since 1.4
703 */
704 public Thread(ThreadGroup group, Runnable target, String name,
705 long stackSize) {
706 this(group, target, name, stackSize, null, true);
707 }
708
709 /**
710 * Allocates a new {@code Thread} object so that it has {@code target}
711 * as its run object, has the specified {@code name} as its name,
712 * belongs to the thread group referred to by {@code group}, has
713 * the specified {@code stackSize}, and inherits initial values for
714 * {@linkplain InheritableThreadLocal inheritable thread-local} variables
715 * if {@code inheritThreadLocals} is {@code true}.
716 *
717 * <p> This constructor is identical to {@link
718 * #Thread(ThreadGroup,Runnable,String,long)} with the added ability to
719 * suppress, or not, the inheriting of initial values for inheritable
720 * thread-local variables from the constructing thread. This allows for
721 * finer grain control over inheritable thread-locals. Care must be taken
722 * when passing a value of {@code false} for {@code inheritThreadLocals},
723 * as it may lead to unexpected behavior if the new thread executes code
724 * that expects a specific thread-local value to be inherited.
725 *
726 * <p> Specifying a value of {@code true} for the {@code inheritThreadLocals}
727 * parameter will cause this constructor to behave exactly like the
728 * {@code Thread(ThreadGroup, Runnable, String, long)} constructor.
729 *
730 * @param group
731 * the thread group. If {@code null} and there is a security
732 * manager, the group is determined by {@linkplain
733 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
734 * If there is not a security manager or {@code
735 * SecurityManager.getThreadGroup()} returns {@code null}, the group
736 * is set to the current thread's thread group.
737 *
738 * @param target
739 * the object whose {@code run} method is invoked when this thread
740 * is started. If {@code null}, this thread's run method is invoked.
741 *
742 * @param name
743 * the name of the new thread
744 *
745 * @param stackSize
746 * the desired stack size for the new thread, or zero to indicate
747 * that this parameter is to be ignored
748 *
749 * @param inheritThreadLocals
750 * if {@code true}, inherit initial values for inheritable
751 * thread-locals from the constructing thread, otherwise no initial
752 * values are inherited
753 *
754 * @throws SecurityException
755 * if the current thread cannot create a thread in the specified
756 * thread group
757 *
758 * @since 9
759 */
760 public Thread(ThreadGroup group, Runnable target, String name,
761 long stackSize, boolean inheritThreadLocals) {
762 this(group, target, name, stackSize, null, inheritThreadLocals);
763 }
764
765 /**
766 * Causes this thread to begin execution; the Java Virtual Machine
767 * calls the {@code run} method of this thread.
768 * <p>
769 * The result is that two threads are running concurrently: the
770 * current thread (which returns from the call to the
771 * {@code start} method) and the other thread (which executes its
772 * {@code run} method).
773 * <p>
774 * It is never legal to start a thread more than once.
775 * In particular, a thread may not be restarted once it has completed
776 * execution.
777 *
778 * @throws IllegalThreadStateException if the thread was already started.
779 * @see #run()
780 * @see #stop()
781 */
782 public synchronized void start() {
783 /**
784 * This method is not invoked for the main method thread or "system"
785 * group threads created/set up by the VM. Any new functionality added
786 * to this method in the future may have to also be added to the VM.
787 *
788 * A zero status value corresponds to state "NEW".
789 */
790 if (threadStatus != 0)
791 throw new IllegalThreadStateException();
792
793 /* Notify the group that this thread is about to be started
794 * so that it can be added to the group's list of threads
795 * and the group's unstarted count can be decremented. */
796 group.add(this);
797
798 boolean started = false;
799 try {
800 start0();
801 started = true;
802 } finally {
803 try {
804 if (!started) {
805 group.threadStartFailed(this);
806 }
807 } catch (Throwable ignore) {
808 /* do nothing. If start0 threw a Throwable then
809 it will be passed up the call stack */
810 }
811 }
812 }
813
814 private native void start0();
815
816 /**
817 * If this thread was constructed using a separate
818 * {@code Runnable} run object, then that
819 * {@code Runnable} object's {@code run} method is called;
820 * otherwise, this method does nothing and returns.
821 * <p>
822 * Subclasses of {@code Thread} should override this method.
823 *
824 * @see #start()
825 * @see #stop()
826 * @see #Thread(ThreadGroup, Runnable, String)
827 */
828 @Override
829 public void run() {
830 if (target != null) {
831 target.run();
832 }
833 }
834
835 /**
836 * This method is called by the system to give a Thread
837 * a chance to clean up before it actually exits.
838 */
839 private void exit() {
840 if (group != null) {
841 group.threadTerminated(this);
842 group = null;
843 }
844 /* Aggressively null out all reference fields: see bug 4006245 */
845 target = null;
846 /* Speed the release of some of these resources */
847 threadLocals = null;
848 inheritableThreadLocals = null;
849 inheritedAccessControlContext = null;
850 blocker = null;
851 uncaughtExceptionHandler = null;
852 }
853
854 /**
855 * Forces the thread to stop executing.
856 * <p>
857 * If there is a security manager installed, its {@code checkAccess}
858 * method is called with {@code this}
859 * as its argument. This may result in a
860 * {@code SecurityException} being raised (in the current thread).
861 * <p>
862 * If this thread is different from the current thread (that is, the current
863 * thread is trying to stop a thread other than itself), the
864 * security manager's {@code checkPermission} method (with a
865 * {@code RuntimePermission("stopThread")} argument) is called in
866 * addition.
867 * Again, this may result in throwing a
868 * {@code SecurityException} (in the current thread).
869 * <p>
870 * The thread represented by this thread is forced to stop whatever
871 * it is doing abnormally and to throw a newly created
872 * {@code ThreadDeath} object as an exception.
873 * <p>
874 * It is permitted to stop a thread that has not yet been started.
875 * If the thread is eventually started, it immediately terminates.
876 * <p>
877 * An application should not normally try to catch
878 * {@code ThreadDeath} unless it must do some extraordinary
879 * cleanup operation (note that the throwing of
880 * {@code ThreadDeath} causes {@code finally} clauses of
881 * {@code try} statements to be executed before the thread
882 * officially dies). If a {@code catch} clause catches a
883 * {@code ThreadDeath} object, it is important to rethrow the
884 * object so that the thread actually dies.
885 * <p>
886 * The top-level error handler that reacts to otherwise uncaught
887 * exceptions does not print out a message or otherwise notify the
888 * application if the uncaught exception is an instance of
889 * {@code ThreadDeath}.
890 *
891 * @throws SecurityException if the current thread cannot
892 * modify this thread.
893 * @see #interrupt()
894 * @see #checkAccess()
895 * @see #run()
896 * @see #start()
897 * @see ThreadDeath
898 * @see ThreadGroup#uncaughtException(Thread,Throwable)
899 * @see SecurityManager#checkAccess(Thread)
900 * @see SecurityManager#checkPermission
901 * @deprecated This method is inherently unsafe. Stopping a thread with
902 * Thread.stop causes it to unlock all of the monitors that it
903 * has locked (as a natural consequence of the unchecked
904 * {@code ThreadDeath} exception propagating up the stack). If
905 * any of the objects previously protected by these monitors were in
906 * an inconsistent state, the damaged objects become visible to
907 * other threads, potentially resulting in arbitrary behavior. Many
908 * uses of {@code stop} should be replaced by code that simply
909 * modifies some variable to indicate that the target thread should
910 * stop running. The target thread should check this variable
911 * regularly, and return from its run method in an orderly fashion
912 * if the variable indicates that it is to stop running. If the
913 * target thread waits for long periods (on a condition variable,
914 * for example), the {@code interrupt} method should be used to
915 * interrupt the wait.
916 * For more information, see
917 * <a href="{@docRoot}/java.base/java/lang/doc-files/threadPrimitiveDeprecation.html">Why
918 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
919 */
920 @Deprecated(since="1.2")
921 public final void stop() {
922 SecurityManager security = System.getSecurityManager();
923 if (security != null) {
924 checkAccess();
925 if (this != Thread.currentThread()) {
926 security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
927 }
928 }
929 // A zero status value corresponds to "NEW", it can't change to
930 // not-NEW because we hold the lock.
931 if (threadStatus != 0) {
932 resume(); // Wake up thread if it was suspended; no-op otherwise
933 }
934
935 // The VM can handle all thread states
936 stop0(new ThreadDeath());
937 }
938
939 /**
940 * Throws {@code UnsupportedOperationException}.
941 *
942 * @param obj ignored
943 *
944 * @deprecated This method was originally designed to force a thread to stop
945 * and throw a given {@code Throwable} as an exception. It was
946 * inherently unsafe (see {@link #stop()} for details), and furthermore
947 * could be used to generate exceptions that the target thread was
948 * not prepared to handle.
949 * For more information, see
950 * <a href="{@docRoot}/java.base/java/lang/doc-files/threadPrimitiveDeprecation.html">Why
951 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
952 * This method is subject to removal in a future version of Java SE.
953 */
954 @Deprecated(since="1.2", forRemoval=true)
955 public final synchronized void stop(Throwable obj) {
956 throw new UnsupportedOperationException();
957 }
958
959 /**
960 * Interrupts this thread.
961 *
962 * <p> Unless the current thread is interrupting itself, which is
963 * always permitted, the {@link #checkAccess() checkAccess} method
964 * of this thread is invoked, which may cause a {@link
965 * SecurityException} to be thrown.
966 *
967 * <p> If this thread is blocked in an invocation of the {@link
968 * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
969 * Object#wait(long, int) wait(long, int)} methods of the {@link Object}
970 * class, or of the {@link #join()}, {@link #join(long)}, {@link
971 * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
972 * methods of this class, then its interrupt status will be cleared and it
973 * will receive an {@link InterruptedException}.
974 *
975 * <p> If this thread is blocked in an I/O operation upon an {@link
976 * java.nio.channels.InterruptibleChannel InterruptibleChannel}
977 * then the channel will be closed, the thread's interrupt
978 * status will be set, and the thread will receive a {@link
979 * java.nio.channels.ClosedByInterruptException}.
980 *
981 * <p> If this thread is blocked in a {@link java.nio.channels.Selector}
982 * then the thread's interrupt status will be set and it will return
983 * immediately from the selection operation, possibly with a non-zero
984 * value, just as if the selector's {@link
985 * java.nio.channels.Selector#wakeup wakeup} method were invoked.
986 *
987 * <p> If none of the previous conditions hold then this thread's interrupt
988 * status will be set. </p>
989 *
990 * <p> Interrupting a thread that is not alive need not have any effect.
991 *
992 * @throws SecurityException
993 * if the current thread cannot modify this thread
994 *
995 * @revised 6.0
996 * @spec JSR-51
997 */
998 public void interrupt() {
999 if (this != Thread.currentThread()) {
1000 checkAccess();
1001
1002 // thread may be blocked in an I/O operation
1003 synchronized (blockerLock) {
1004 Interruptible b = blocker;
1005 if (b != null) {
1006 interrupt0(); // set interrupt status
1007 b.interrupt(this);
1008 return;
1009 }
1010 }
1011 }
1012
1013 // set interrupt status
1014 interrupt0();
1015 }
1016
1017 /**
1018 * Tests whether the current thread has been interrupted. The
1019 * <i>interrupted status</i> of the thread is cleared by this method. In
1020 * other words, if this method were to be called twice in succession, the
1021 * second call would return false (unless the current thread were
1022 * interrupted again, after the first call had cleared its interrupted
1023 * status and before the second call had examined it).
1024 *
1025 * <p>A thread interruption ignored because a thread was not alive
1026 * at the time of the interrupt will be reflected by this method
1027 * returning false.
1028 *
1029 * @return {@code true} if the current thread has been interrupted;
1030 * {@code false} otherwise.
1031 * @see #isInterrupted()
1032 * @revised 6.0
1033 */
1034 public static boolean interrupted() {
1035 return currentThread().isInterrupted(true);
1036 }
1037
1038 /**
1039 * Tests whether this thread has been interrupted. The <i>interrupted
1040 * status</i> of the thread is unaffected by this method.
1041 *
1042 * <p>A thread interruption ignored because a thread was not alive
1043 * at the time of the interrupt will be reflected by this method
1044 * returning false.
1045 *
1046 * @return {@code true} if this thread has been interrupted;
1047 * {@code false} otherwise.
1048 * @see #interrupted()
1049 * @revised 6.0
1050 */
1051 public boolean isInterrupted() {
1052 return isInterrupted(false);
1053 }
1054
1055 /**
1056 * Tests if some Thread has been interrupted. The interrupted state
1057 * is reset or not based on the value of ClearInterrupted that is
1058 * passed.
1059 */
1060 @HotSpotIntrinsicCandidate
1061 private native boolean isInterrupted(boolean ClearInterrupted);
1062
1063 /**
1064 * Throws {@link NoSuchMethodError}.
1065 *
1066 * @deprecated This method was originally designed to destroy this
1067 * thread without any cleanup. Any monitors it held would have
1068 * remained locked. However, the method was never implemented.
1069 * If it were to be implemented, it would be deadlock-prone in
1070 * much the manner of {@link #suspend}. If the target thread held
1071 * a lock protecting a critical system resource when it was
1072 * destroyed, no thread could ever access this resource again.
1073 * If another thread ever attempted to lock this resource, deadlock
1074 * would result. Such deadlocks typically manifest themselves as
1075 * "frozen" processes. For more information, see
1076 * <a href="{@docRoot}/java.base/java/lang/doc-files/threadPrimitiveDeprecation.html">
1077 * Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1078 * This method is subject to removal in a future version of Java SE.
1079 * @throws NoSuchMethodError always
1080 */
1081 @Deprecated(since="1.5", forRemoval=true)
1082 public void destroy() {
1083 throw new NoSuchMethodError();
1084 }
1085
1086 /**
1087 * Tests if this thread is alive. A thread is alive if it has
1088 * been started and has not yet died.
1089 *
1090 * @return {@code true} if this thread is alive;
1091 * {@code false} otherwise.
1092 */
1093 public final native boolean isAlive();
1094
1095 /**
1096 * Suspends this thread.
1097 * <p>
1098 * First, the {@code checkAccess} method of this thread is called
1099 * with no arguments. This may result in throwing a
1100 * {@code SecurityException }(in the current thread).
1101 * <p>
1102 * If the thread is alive, it is suspended and makes no further
1103 * progress unless and until it is resumed.
1104 *
1105 * @throws SecurityException if the current thread cannot modify
1106 * this thread.
1107 * @see #checkAccess
1108 * @deprecated This method has been deprecated, as it is
1109 * inherently deadlock-prone. If the target thread holds a lock on the
1110 * monitor protecting a critical system resource when it is suspended, no
1111 * thread can access this resource until the target thread is resumed. If
1112 * the thread that would resume the target thread attempts to lock this
1113 * monitor prior to calling {@code resume}, deadlock results. Such
1114 * deadlocks typically manifest themselves as "frozen" processes.
1115 * For more information, see
1116 * <a href="{@docRoot}/java.base/java/lang/doc-files/threadPrimitiveDeprecation.html">Why
1117 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1118 */
1119 @Deprecated(since="1.2")
1120 public final void suspend() {
1121 checkAccess();
1122 suspend0();
1123 }
1124
1125 /**
1126 * Resumes a suspended thread.
1127 * <p>
1128 * First, the {@code checkAccess} method of this thread is called
1129 * with no arguments. This may result in throwing a
1130 * {@code SecurityException} (in the current thread).
1131 * <p>
1132 * If the thread is alive but suspended, it is resumed and is
1133 * permitted to make progress in its execution.
1134 *
1135 * @throws SecurityException if the current thread cannot modify this
1136 * thread.
1137 * @see #checkAccess
1138 * @see #suspend()
1139 * @deprecated This method exists solely for use with {@link #suspend},
1140 * which has been deprecated because it is deadlock-prone.
1141 * For more information, see
1142 * <a href="{@docRoot}/java.base/java/lang/doc-files/threadPrimitiveDeprecation.html">Why
1143 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1144 */
1145 @Deprecated(since="1.2")
1146 public final void resume() {
1147 checkAccess();
1148 resume0();
1149 }
1150
1151 /**
1152 * Changes the priority of this thread.
1153 * <p>
1154 * First the {@code checkAccess} method of this thread is called
1155 * with no arguments. This may result in throwing a {@code SecurityException}.
1156 * <p>
1157 * Otherwise, the priority of this thread is set to the smaller of
1158 * the specified {@code newPriority} and the maximum permitted
1159 * priority of the thread's thread group.
1160 *
1161 * @param newPriority priority to set this thread to
1162 * @throws IllegalArgumentException If the priority is not in the
1163 * range {@code MIN_PRIORITY} to
1164 * {@code MAX_PRIORITY}.
1165 * @throws SecurityException if the current thread cannot modify
1166 * this thread.
1167 * @see #getPriority
1168 * @see #checkAccess()
1169 * @see #getThreadGroup()
1170 * @see #MAX_PRIORITY
1171 * @see #MIN_PRIORITY
1172 * @see ThreadGroup#getMaxPriority()
1173 */
1174 public final void setPriority(int newPriority) {
1175 ThreadGroup g;
1176 checkAccess();
1177 if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
1178 throw new IllegalArgumentException();
1179 }
1180 if((g = getThreadGroup()) != null) {
1181 if (newPriority > g.getMaxPriority()) {
1182 newPriority = g.getMaxPriority();
1183 }
1184 setPriority0(priority = newPriority);
1185 }
1186 }
1187
1188 /**
1189 * Returns this thread's priority.
1190 *
1191 * @return this thread's priority.
1192 * @see #setPriority
1193 */
1194 public final int getPriority() {
1195 return priority;
1196 }
1197
1198 /**
1199 * Changes the name of this thread to be equal to the argument {@code name}.
1200 * <p>
1201 * First the {@code checkAccess} method of this thread is called
1202 * with no arguments. This may result in throwing a
1203 * {@code SecurityException}.
1204 *
1205 * @param name the new name for this thread.
1206 * @throws SecurityException if the current thread cannot modify this
1207 * thread.
1208 * @see #getName
1209 * @see #checkAccess()
1210 */
1211 public final synchronized void setName(String name) {
1212 checkAccess();
1213 if (name == null) {
1214 throw new NullPointerException("name cannot be null");
1215 }
1216
1217 this.name = name;
1218 if (threadStatus != 0) {
1219 setNativeName(name);
1220 }
1221 }
1222
1223 /**
1224 * Returns this thread's name.
1225 *
1226 * @return this thread's name.
1227 * @see #setName(String)
1228 */
1229 public final String getName() {
1230 return name;
1231 }
1232
1233 /**
1234 * Returns the thread group to which this thread belongs.
1235 * This method returns null if this thread has died
1236 * (been stopped).
1237 *
1238 * @return this thread's thread group.
1239 */
1240 public final ThreadGroup getThreadGroup() {
1241 return group;
1242 }
1243
1244 /**
1245 * Returns an estimate of the number of active threads in the current
1246 * thread's {@linkplain java.lang.ThreadGroup thread group} and its
1247 * subgroups. Recursively iterates over all subgroups in the current
1248 * thread's thread group.
1249 *
1250 * <p> The value returned is only an estimate because the number of
1251 * threads may change dynamically while this method traverses internal
1252 * data structures, and might be affected by the presence of certain
1253 * system threads. This method is intended primarily for debugging
1254 * and monitoring purposes.
1255 *
1256 * @return an estimate of the number of active threads in the current
1257 * thread's thread group and in any other thread group that
1258 * has the current thread's thread group as an ancestor
1259 */
1260 public static int activeCount() {
1261 return currentThread().getThreadGroup().activeCount();
1262 }
1263
1264 /**
1265 * Copies into the specified array every active thread in the current
1266 * thread's thread group and its subgroups. This method simply
1267 * invokes the {@link java.lang.ThreadGroup#enumerate(Thread[])}
1268 * method of the current thread's thread group.
1269 *
1270 * <p> An application might use the {@linkplain #activeCount activeCount}
1271 * method to get an estimate of how big the array should be, however
1272 * <i>if the array is too short to hold all the threads, the extra threads
1273 * are silently ignored.</i> If it is critical to obtain every active
1274 * thread in the current thread's thread group and its subgroups, the
1275 * invoker should verify that the returned int value is strictly less
1276 * than the length of {@code tarray}.
1277 *
1278 * <p> Due to the inherent race condition in this method, it is recommended
1279 * that the method only be used for debugging and monitoring purposes.
1280 *
1281 * @param tarray
1282 * an array into which to put the list of threads
1283 *
1284 * @return the number of threads put into the array
1285 *
1286 * @throws SecurityException
1287 * if {@link java.lang.ThreadGroup#checkAccess} determines that
1288 * the current thread cannot access its thread group
1289 */
1290 public static int enumerate(Thread tarray[]) {
1291 return currentThread().getThreadGroup().enumerate(tarray);
1292 }
1293
1294 /**
1295 * Counts the number of stack frames in this thread. The thread must
1296 * be suspended.
1297 *
1298 * @return the number of stack frames in this thread.
1299 * @throws IllegalThreadStateException if this thread is not
1300 * suspended.
1301 * @deprecated The definition of this call depends on {@link #suspend},
1302 * which is deprecated. Further, the results of this call
1303 * were never well-defined.
1304 * This method is subject to removal in a future version of Java SE.
1305 * @see StackWalker
1306 */
1307 @Deprecated(since="1.2", forRemoval=true)
1308 public native int countStackFrames();
1309
1310 /**
1311 * Waits at most {@code millis} milliseconds for this thread to
1312 * die. A timeout of {@code 0} means to wait forever.
1313 *
1314 * <p> This implementation uses a loop of {@code this.wait} calls
1315 * conditioned on {@code this.isAlive}. As a thread terminates the
1316 * {@code this.notifyAll} method is invoked. It is recommended that
1317 * applications not use {@code wait}, {@code notify}, or
1318 * {@code notifyAll} on {@code Thread} instances.
1319 *
1320 * @param millis
1321 * the time to wait in milliseconds
1322 *
1323 * @throws IllegalArgumentException
1324 * if the value of {@code millis} is negative
1325 *
1326 * @throws InterruptedException
1327 * if any thread has interrupted the current thread. The
1328 * <i>interrupted status</i> of the current thread is
1329 * cleared when this exception is thrown.
1330 */
1331 public final synchronized void join(long millis)
1332 throws InterruptedException {
1333 long base = System.currentTimeMillis();
1334 long now = 0;
1335
1336 if (millis < 0) {
1337 throw new IllegalArgumentException("timeout value is negative");
1338 }
1339
1340 if (millis == 0) {
1341 while (isAlive()) {
1342 wait(0);
1343 }
1344 } else {
1345 while (isAlive()) {
1346 long delay = millis - now;
1347 if (delay <= 0) {
1348 break;
1349 }
1350 wait(delay);
1351 now = System.currentTimeMillis() - base;
1352 }
1353 }
1354 }
1355
1356 /**
1357 * Waits at most {@code millis} milliseconds plus
1358 * {@code nanos} nanoseconds for this thread to die.
1359 *
1360 * <p> This implementation uses a loop of {@code this.wait} calls
1361 * conditioned on {@code this.isAlive}. As a thread terminates the
1362 * {@code this.notifyAll} method is invoked. It is recommended that
1363 * applications not use {@code wait}, {@code notify}, or
1364 * {@code notifyAll} on {@code Thread} instances.
1365 *
1366 * @param millis
1367 * the time to wait in milliseconds
1368 *
1369 * @param nanos
1370 * {@code 0-999999} additional nanoseconds to wait
1371 *
1372 * @throws IllegalArgumentException
1373 * if the value of {@code millis} is negative, or the value
1374 * of {@code nanos} is not in the range {@code 0-999999}
1375 *
1376 * @throws InterruptedException
1377 * if any thread has interrupted the current thread. The
1378 * <i>interrupted status</i> of the current thread is
1379 * cleared when this exception is thrown.
1380 */
1381 public final synchronized void join(long millis, int nanos)
1382 throws InterruptedException {
1383
1384 if (millis < 0) {
1385 throw new IllegalArgumentException("timeout value is negative");
1386 }
1387
1388 if (nanos < 0 || nanos > 999999) {
1389 throw new IllegalArgumentException(
1390 "nanosecond timeout value out of range");
1391 }
1392
1393 if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
1394 millis++;
1395 }
1396
1397 join(millis);
1398 }
1399
1400 /**
1401 * Waits for this thread to die.
1402 *
1403 * <p> An invocation of this method behaves in exactly the same
1404 * way as the invocation
1405 *
1406 * <blockquote>
1407 * {@linkplain #join(long) join}{@code (0)}
1408 * </blockquote>
1409 *
1410 * @throws InterruptedException
1411 * if any thread has interrupted the current thread. The
1412 * <i>interrupted status</i> of the current thread is
1413 * cleared when this exception is thrown.
1414 */
1415 public final void join() throws InterruptedException {
1416 join(0);
1417 }
1418
1419 /**
1420 * Prints a stack trace of the current thread to the standard error stream.
1421 * This method is used only for debugging.
1422 */
1423 public static void dumpStack() {
1424 new Exception("Stack trace").printStackTrace();
1425 }
1426
1427 /**
1428 * Marks this thread as either a {@linkplain #isDaemon daemon} thread
1429 * or a user thread. The Java Virtual Machine exits when the only
1430 * threads running are all daemon threads.
1431 *
1432 * <p> This method must be invoked before the thread is started.
1433 *
1434 * @param on
1435 * if {@code true}, marks this thread as a daemon thread
1436 *
1437 * @throws IllegalThreadStateException
1438 * if this thread is {@linkplain #isAlive alive}
1439 *
1440 * @throws SecurityException
1441 * if {@link #checkAccess} determines that the current
1442 * thread cannot modify this thread
1443 */
1444 public final void setDaemon(boolean on) {
1445 checkAccess();
1446 if (isAlive()) {
1447 throw new IllegalThreadStateException();
1448 }
1449 daemon = on;
1450 }
1451
1452 /**
1453 * Tests if this thread is a daemon thread.
1454 *
1455 * @return {@code true} if this thread is a daemon thread;
1456 * {@code false} otherwise.
1457 * @see #setDaemon(boolean)
1458 */
1459 public final boolean isDaemon() {
1460 return daemon;
1461 }
1462
1463 /**
1464 * Determines if the currently running thread has permission to
1465 * modify this thread.
1466 * <p>
1467 * If there is a security manager, its {@code checkAccess} method
1468 * is called with this thread as its argument. This may result in
1469 * throwing a {@code SecurityException}.
1470 *
1471 * @throws SecurityException if the current thread is not allowed to
1472 * access this thread.
1473 * @see SecurityManager#checkAccess(Thread)
1474 */
1475 public final void checkAccess() {
1476 SecurityManager security = System.getSecurityManager();
1477 if (security != null) {
1478 security.checkAccess(this);
1479 }
1480 }
1481
1482 /**
1483 * Returns a string representation of this thread, including the
1484 * thread's name, priority, and thread group.
1485 *
1486 * @return a string representation of this thread.
1487 */
1488 public String toString() {
1489 ThreadGroup group = getThreadGroup();
1490 if (group != null) {
1491 return "Thread[" + getName() + "," + getPriority() + "," +
1492 group.getName() + "]";
1493 } else {
1494 return "Thread[" + getName() + "," + getPriority() + "," +
1495 "" + "]";
1496 }
1497 }
1498
1499 /**
1500 * Returns the context {@code ClassLoader} for this thread. The context
1501 * {@code ClassLoader} is provided by the creator of the thread for use
1502 * by code running in this thread when loading classes and resources.
1503 * If not {@linkplain #setContextClassLoader set}, the default is the
1504 * {@code ClassLoader} context of the parent thread. The context
1505 * {@code ClassLoader} of the
1506 * primordial thread is typically set to the class loader used to load the
1507 * application.
1508 *
1509 *
1510 * @return the context {@code ClassLoader} for this thread, or {@code null}
1511 * indicating the system class loader (or, failing that, the
1512 * bootstrap class loader)
1513 *
1514 * @throws SecurityException
1515 * if a security manager is present, and the caller's class loader
1516 * is not {@code null} and is not the same as or an ancestor of the
1517 * context class loader, and the caller does not have the
1518 * {@link RuntimePermission}{@code ("getClassLoader")}
1519 *
1520 * @since 1.2
1521 */
1522 @CallerSensitive
1523 public ClassLoader getContextClassLoader() {
1524 if (contextClassLoader == null)
1525 return null;
1526 SecurityManager sm = System.getSecurityManager();
1527 if (sm != null) {
1528 ClassLoader.checkClassLoaderPermission(contextClassLoader,
1529 Reflection.getCallerClass());
1530 }
1531 return contextClassLoader;
1532 }
1533
1534 /**
1535 * Sets the context ClassLoader for this Thread. The context
1536 * ClassLoader can be set when a thread is created, and allows
1537 * the creator of the thread to provide the appropriate class loader,
1538 * through {@code getContextClassLoader}, to code running in the thread
1539 * when loading classes and resources.
1540 *
1541 * <p>If a security manager is present, its {@link
1542 * SecurityManager#checkPermission(java.security.Permission) checkPermission}
1543 * method is invoked with a {@link RuntimePermission RuntimePermission}{@code
1544 * ("setContextClassLoader")} permission to see if setting the context
1545 * ClassLoader is permitted.
1546 *
1547 * @param cl
1548 * the context ClassLoader for this Thread, or null indicating the
1549 * system class loader (or, failing that, the bootstrap class loader)
1550 *
1551 * @throws SecurityException
1552 * if the current thread cannot set the context ClassLoader
1553 *
1554 * @since 1.2
1555 */
1556 public void setContextClassLoader(ClassLoader cl) {
1557 SecurityManager sm = System.getSecurityManager();
1558 if (sm != null) {
1559 sm.checkPermission(new RuntimePermission("setContextClassLoader"));
1560 }
1561 contextClassLoader = cl;
1562 }
1563
1564 /**
1565 * Returns {@code true} if and only if the current thread holds the
1566 * monitor lock on the specified object.
1567 *
1568 * <p>This method is designed to allow a program to assert that
1569 * the current thread already holds a specified lock:
1570 * <pre>
1571 * assert Thread.holdsLock(obj);
1572 * </pre>
1573 *
1574 * @param obj the object on which to test lock ownership
1575 * @throws NullPointerException if obj is {@code null}
1576 * @return {@code true} if the current thread holds the monitor lock on
1577 * the specified object.
1578 * @since 1.4
1579 */
1580 public static native boolean holdsLock(Object obj);
1581
1582 private static final StackTraceElement[] EMPTY_STACK_TRACE
1583 = new StackTraceElement[0];
1584
1585 /**
1586 * Returns an array of stack trace elements representing the stack dump
1587 * of this thread. This method will return a zero-length array if
1588 * this thread has not started, has started but has not yet been
1589 * scheduled to run by the system, or has terminated.
1590 * If the returned array is of non-zero length then the first element of
1591 * the array represents the top of the stack, which is the most recent
1592 * method invocation in the sequence. The last element of the array
1593 * represents the bottom of the stack, which is the least recent method
1594 * invocation in the sequence.
1595 *
1596 * <p>If there is a security manager, and this thread is not
1597 * the current thread, then the security manager's
1598 * {@code checkPermission} method is called with a
1599 * {@code RuntimePermission("getStackTrace")} permission
1600 * to see if it's ok to get the stack trace.
1601 *
1602 * <p>Some virtual machines may, under some circumstances, omit one
1603 * or more stack frames from the stack trace. In the extreme case,
1604 * a virtual machine that has no stack trace information concerning
1605 * this thread is permitted to return a zero-length array from this
1606 * method.
1607 *
1608 * @return an array of {@code StackTraceElement},
1609 * each represents one stack frame.
1610 *
1611 * @throws SecurityException
1612 * if a security manager exists and its
1613 * {@code checkPermission} method doesn't allow
1614 * getting the stack trace of thread.
1615 * @see SecurityManager#checkPermission
1616 * @see RuntimePermission
1617 * @see Throwable#getStackTrace
1618 *
1619 * @since 1.5
1620 */
1621 public StackTraceElement[] getStackTrace() {
1622 if (this != Thread.currentThread()) {
1623 // check for getStackTrace permission
1624 SecurityManager security = System.getSecurityManager();
1625 if (security != null) {
1626 security.checkPermission(
1627 SecurityConstants.GET_STACK_TRACE_PERMISSION);
1628 }
1629 // optimization so we do not call into the vm for threads that
1630 // have not yet started or have terminated
1631 if (!isAlive()) {
1632 return EMPTY_STACK_TRACE;
1633 }
1634 StackTraceElement[][] stackTraceArray = dumpThreads(new Thread[] {this});
1635 StackTraceElement[] stackTrace = stackTraceArray[0];
1636 // a thread that was alive during the previous isAlive call may have
1637 // since terminated, therefore not having a stacktrace.
1638 if (stackTrace == null) {
1639 stackTrace = EMPTY_STACK_TRACE;
1640 }
1641 return stackTrace;
1642 } else {
1643 return (new Exception()).getStackTrace();
1644 }
1645 }
1646
1647 /**
1648 * Returns a map of stack traces for all live threads.
1649 * The map keys are threads and each map value is an array of
1650 * {@code StackTraceElement} that represents the stack dump
1651 * of the corresponding {@code Thread}.
1652 * The returned stack traces are in the format specified for
1653 * the {@link #getStackTrace getStackTrace} method.
1654 *
1655 * <p>The threads may be executing while this method is called.
1656 * The stack trace of each thread only represents a snapshot and
1657 * each stack trace may be obtained at different time. A zero-length
1658 * array will be returned in the map value if the virtual machine has
1659 * no stack trace information about a thread.
1660 *
1661 * <p>If there is a security manager, then the security manager's
1662 * {@code checkPermission} method is called with a
1663 * {@code RuntimePermission("getStackTrace")} permission as well as
1664 * {@code RuntimePermission("modifyThreadGroup")} permission
1665 * to see if it is ok to get the stack trace of all threads.
1666 *
1667 * @return a {@code Map} from {@code Thread} to an array of
1668 * {@code StackTraceElement} that represents the stack trace of
1669 * the corresponding thread.
1670 *
1671 * @throws SecurityException
1672 * if a security manager exists and its
1673 * {@code checkPermission} method doesn't allow
1674 * getting the stack trace of thread.
1675 * @see #getStackTrace
1676 * @see SecurityManager#checkPermission
1677 * @see RuntimePermission
1678 * @see Throwable#getStackTrace
1679 *
1680 * @since 1.5
1681 */
1682 public static Map<Thread, StackTraceElement[]> getAllStackTraces() {
1683 // check for getStackTrace permission
1684 SecurityManager security = System.getSecurityManager();
1685 if (security != null) {
1686 security.checkPermission(
1687 SecurityConstants.GET_STACK_TRACE_PERMISSION);
1688 security.checkPermission(
1689 SecurityConstants.MODIFY_THREADGROUP_PERMISSION);
1690 }
1691
1692 // Get a snapshot of the list of all threads
1693 Thread[] threads = getThreads();
1694 StackTraceElement[][] traces = dumpThreads(threads);
1695 Map<Thread, StackTraceElement[]> m = new HashMap<>(threads.length);
1696 for (int i = 0; i < threads.length; i++) {
1697 StackTraceElement[] stackTrace = traces[i];
1698 if (stackTrace != null) {
1699 m.put(threads[i], stackTrace);
1700 }
1701 // else terminated so we don't put it in the map
1702 }
1703 return m;
1704 }
1705
1706
1707 private static final RuntimePermission SUBCLASS_IMPLEMENTATION_PERMISSION =
1708 new RuntimePermission("enableContextClassLoaderOverride");
1709
1710 /** cache of subclass security audit results */
1711 /* Replace with ConcurrentReferenceHashMap when/if it appears in a future
1712 * release */
1713 private static class Caches {
1714 /** cache of subclass security audit results */
1715 static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits =
1716 new ConcurrentHashMap<>();
1717
1718 /** queue for WeakReferences to audited subclasses */
1719 static final ReferenceQueue<Class<?>> subclassAuditsQueue =
1720 new ReferenceQueue<>();
1721 }
1722
1723 /**
1724 * Verifies that this (possibly subclass) instance can be constructed
1725 * without violating security constraints: the subclass must not override
1726 * security-sensitive non-final methods, or else the
1727 * "enableContextClassLoaderOverride" RuntimePermission is checked.
1728 */
1729 private static boolean isCCLOverridden(Class<?> cl) {
1730 if (cl == Thread.class)
1731 return false;
1732
1733 processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits);
1734 WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue);
1735 Boolean result = Caches.subclassAudits.get(key);
1736 if (result == null) {
1737 result = Boolean.valueOf(auditSubclass(cl));
1738 Caches.subclassAudits.putIfAbsent(key, result);
1739 }
1740
1741 return result.booleanValue();
1742 }
1743
1744 /**
1745 * Performs reflective checks on given subclass to verify that it doesn't
1746 * override security-sensitive non-final methods. Returns true if the
1747 * subclass overrides any of the methods, false otherwise.
1748 */
1749 private static boolean auditSubclass(final Class<?> subcl) {
1750 Boolean result = AccessController.doPrivileged(
1751 new PrivilegedAction<>() {
1752 public Boolean run() {
1753 for (Class<?> cl = subcl;
1754 cl != Thread.class;
1755 cl = cl.getSuperclass())
1756 {
1757 try {
1758 cl.getDeclaredMethod("getContextClassLoader", new Class<?>[0]);
1759 return Boolean.TRUE;
1760 } catch (NoSuchMethodException ex) {
1761 }
1762 try {
1763 Class<?>[] params = {ClassLoader.class};
1764 cl.getDeclaredMethod("setContextClassLoader", params);
1765 return Boolean.TRUE;
1766 } catch (NoSuchMethodException ex) {
1767 }
1768 }
1769 return Boolean.FALSE;
1770 }
1771 }
1772 );
1773 return result.booleanValue();
1774 }
1775
1776 private static native StackTraceElement[][] dumpThreads(Thread[] threads);
1777 private static native Thread[] getThreads();
1778
1779 /**
1780 * Returns the identifier of this Thread. The thread ID is a positive
1781 * {@code long} number generated when this thread was created.
1782 * The thread ID is unique and remains unchanged during its lifetime.
1783 * When a thread is terminated, this thread ID may be reused.
1784 *
1785 * @return this thread's ID.
1786 * @since 1.5
1787 */
1788 public long getId() {
1789 return tid;
1790 }
1791
1792 /**
1793 * A thread state. A thread can be in one of the following states:
1794 * <ul>
1795 * <li>{@link #NEW}<br>
1796 * A thread that has not yet started is in this state.
1797 * </li>
1798 * <li>{@link #RUNNABLE}<br>
1799 * A thread executing in the Java virtual machine is in this state.
1800 * </li>
1801 * <li>{@link #BLOCKED}<br>
1802 * A thread that is blocked waiting for a monitor lock
1803 * is in this state.
1804 * </li>
1805 * <li>{@link #WAITING}<br>
1806 * A thread that is waiting indefinitely for another thread to
1807 * perform a particular action is in this state.
1808 * </li>
1809 * <li>{@link #TIMED_WAITING}<br>
1810 * A thread that is waiting for another thread to perform an action
1811 * for up to a specified waiting time is in this state.
1812 * </li>
1813 * <li>{@link #TERMINATED}<br>
1814 * A thread that has exited is in this state.
1815 * </li>
1816 * </ul>
1817 *
1818 * <p>
1819 * A thread can be in only one state at a given point in time.
1820 * These states are virtual machine states which do not reflect
1821 * any operating system thread states.
1822 *
1823 * @since 1.5
1824 * @see #getState
1825 */
1826 public enum State {
1827 /**
1828 * Thread state for a thread which has not yet started.
1829 */
1830 NEW,
1831
1832 /**
1833 * Thread state for a runnable thread. A thread in the runnable
1834 * state is executing in the Java virtual machine but it may
1835 * be waiting for other resources from the operating system
1836 * such as processor.
1837 */
1838 RUNNABLE,
1839
1840 /**
1841 * Thread state for a thread blocked waiting for a monitor lock.
1842 * A thread in the blocked state is waiting for a monitor lock
1843 * to enter a synchronized block/method or
1844 * reenter a synchronized block/method after calling
1845 * {@link Object#wait() Object.wait}.
1846 */
1847 BLOCKED,
1848
1849 /**
1850 * Thread state for a waiting thread.
1851 * A thread is in the waiting state due to calling one of the
1852 * following methods:
1853 * <ul>
1854 * <li>{@link Object#wait() Object.wait} with no timeout</li>
1855 * <li>{@link #join() Thread.join} with no timeout</li>
1856 * <li>{@link LockSupport#park() LockSupport.park}</li>
1857 * </ul>
1858 *
1859 * <p>A thread in the waiting state is waiting for another thread to
1860 * perform a particular action.
1861 *
1862 * For example, a thread that has called {@code Object.wait()}
1863 * on an object is waiting for another thread to call
1864 * {@code Object.notify()} or {@code Object.notifyAll()} on
1865 * that object. A thread that has called {@code Thread.join()}
1866 * is waiting for a specified thread to terminate.
1867 */
1868 WAITING,
1869
1870 /**
1871 * Thread state for a waiting thread with a specified waiting time.
1872 * A thread is in the timed waiting state due to calling one of
1873 * the following methods with a specified positive waiting time:
1874 * <ul>
1875 * <li>{@link #sleep Thread.sleep}</li>
1876 * <li>{@link Object#wait(long) Object.wait} with timeout</li>
1877 * <li>{@link #join(long) Thread.join} with timeout</li>
1878 * <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
1879 * <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
1880 * </ul>
1881 */
1882 TIMED_WAITING,
1883
1884 /**
1885 * Thread state for a terminated thread.
1886 * The thread has completed execution.
1887 */
1888 TERMINATED;
1889 }
1890
1891 /**
1892 * Returns the state of this thread.
1893 * This method is designed for use in monitoring of the system state,
1894 * not for synchronization control.
1895 *
1896 * @return this thread's state.
1897 * @since 1.5
1898 */
1899 public State getState() {
1900 // get current thread state
1901 return jdk.internal.misc.VM.toThreadState(threadStatus);
1902 }
1903
1904 // Added in JSR-166
1905
1906 /**
1907 * Interface for handlers invoked when a {@code Thread} abruptly
1908 * terminates due to an uncaught exception.
1909 * <p>When a thread is about to terminate due to an uncaught exception
1910 * the Java Virtual Machine will query the thread for its
1911 * {@code UncaughtExceptionHandler} using
1912 * {@link #getUncaughtExceptionHandler} and will invoke the handler's
1913 * {@code uncaughtException} method, passing the thread and the
1914 * exception as arguments.
1915 * If a thread has not had its {@code UncaughtExceptionHandler}
1916 * explicitly set, then its {@code ThreadGroup} object acts as its
1917 * {@code UncaughtExceptionHandler}. If the {@code ThreadGroup} object
1918 * has no
1919 * special requirements for dealing with the exception, it can forward
1920 * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler
1921 * default uncaught exception handler}.
1922 *
1923 * @see #setDefaultUncaughtExceptionHandler
1924 * @see #setUncaughtExceptionHandler
1925 * @see ThreadGroup#uncaughtException
1926 * @since 1.5
1927 */
1928 @FunctionalInterface
1929 public interface UncaughtExceptionHandler {
1930 /**
1931 * Method invoked when the given thread terminates due to the
1932 * given uncaught exception.
1933 * <p>Any exception thrown by this method will be ignored by the
1934 * Java Virtual Machine.
1935 * @param t the thread
1936 * @param e the exception
1937 */
1938 void uncaughtException(Thread t, Throwable e);
1939 }
1940
1941 // null unless explicitly set
1942 private volatile UncaughtExceptionHandler uncaughtExceptionHandler;
1943
1944 // null unless explicitly set
1945 private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler;
1946
1947 /**
1948 * Set the default handler invoked when a thread abruptly terminates
1949 * due to an uncaught exception, and no other handler has been defined
1950 * for that thread.
1951 *
1952 * <p>Uncaught exception handling is controlled first by the thread, then
1953 * by the thread's {@link ThreadGroup} object and finally by the default
1954 * uncaught exception handler. If the thread does not have an explicit
1955 * uncaught exception handler set, and the thread's thread group
1956 * (including parent thread groups) does not specialize its
1957 * {@code uncaughtException} method, then the default handler's
1958 * {@code uncaughtException} method will be invoked.
1959 * <p>By setting the default uncaught exception handler, an application
1960 * can change the way in which uncaught exceptions are handled (such as
1961 * logging to a specific device, or file) for those threads that would
1962 * already accept whatever "default" behavior the system
1963 * provided.
1964 *
1965 * <p>Note that the default uncaught exception handler should not usually
1966 * defer to the thread's {@code ThreadGroup} object, as that could cause
1967 * infinite recursion.
1968 *
1969 * @param eh the object to use as the default uncaught exception handler.
1970 * If {@code null} then there is no default handler.
1971 *
1972 * @throws SecurityException if a security manager is present and it denies
1973 * {@link RuntimePermission}{@code ("setDefaultUncaughtExceptionHandler")}
1974 *
1975 * @see #setUncaughtExceptionHandler
1976 * @see #getUncaughtExceptionHandler
1977 * @see ThreadGroup#uncaughtException
1978 * @since 1.5
1979 */
1980 public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
1981 SecurityManager sm = System.getSecurityManager();
1982 if (sm != null) {
1983 sm.checkPermission(
1984 new RuntimePermission("setDefaultUncaughtExceptionHandler")
1985 );
1986 }
1987
1988 defaultUncaughtExceptionHandler = eh;
1989 }
1990
1991 /**
1992 * Returns the default handler invoked when a thread abruptly terminates
1993 * due to an uncaught exception. If the returned value is {@code null},
1994 * there is no default.
1995 * @since 1.5
1996 * @see #setDefaultUncaughtExceptionHandler
1997 * @return the default uncaught exception handler for all threads
1998 */
1999 public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler(){
2000 return defaultUncaughtExceptionHandler;
2001 }
2002
2003 /**
2004 * Returns the handler invoked when this thread abruptly terminates
2005 * due to an uncaught exception. If this thread has not had an
2006 * uncaught exception handler explicitly set then this thread's
2007 * {@code ThreadGroup} object is returned, unless this thread
2008 * has terminated, in which case {@code null} is returned.
2009 * @since 1.5
2010 * @return the uncaught exception handler for this thread
2011 */
2012 public UncaughtExceptionHandler getUncaughtExceptionHandler() {
2013 return uncaughtExceptionHandler != null ?
2014 uncaughtExceptionHandler : group;
2015 }
2016
2017 /**
2018 * Set the handler invoked when this thread abruptly terminates
2019 * due to an uncaught exception.
2020 * <p>A thread can take full control of how it responds to uncaught
2021 * exceptions by having its uncaught exception handler explicitly set.
2022 * If no such handler is set then the thread's {@code ThreadGroup}
2023 * object acts as its handler.
2024 * @param eh the object to use as this thread's uncaught exception
2025 * handler. If {@code null} then this thread has no explicit handler.
2026 * @throws SecurityException if the current thread is not allowed to
2027 * modify this thread.
2028 * @see #setDefaultUncaughtExceptionHandler
2029 * @see ThreadGroup#uncaughtException
2030 * @since 1.5
2031 */
2032 public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
2033 checkAccess();
2034 uncaughtExceptionHandler = eh;
2035 }
2036
2037 /**
2038 * Dispatch an uncaught exception to the handler. This method is
2039 * intended to be called only by the JVM.
2040 */
2041 private void dispatchUncaughtException(Throwable e) {
2042 getUncaughtExceptionHandler().uncaughtException(this, e);
2043 }
2044
2045 /**
2046 * Removes from the specified map any keys that have been enqueued
2047 * on the specified reference queue.
2048 */
2049 static void processQueue(ReferenceQueue<Class<?>> queue,
2050 ConcurrentMap<? extends
2051 WeakReference<Class<?>>, ?> map)
2052 {
2053 Reference<? extends Class<?>> ref;
2054 while((ref = queue.poll()) != null) {
2055 map.remove(ref);
2056 }
2057 }
2058
2059 /**
2060 * Weak key for Class objects.
2061 **/
2062 static class WeakClassKey extends WeakReference<Class<?>> {
2063 /**
2064 * saved value of the referent's identity hash code, to maintain
2065 * a consistent hash code after the referent has been cleared
2066 */
2067 private final int hash;
2068
2069 /**
2070 * Create a new WeakClassKey to the given object, registered
2071 * with a queue.
2072 */
2073 WeakClassKey(Class<?> cl, ReferenceQueue<Class<?>> refQueue) {
2074 super(cl, refQueue);
2075 hash = System.identityHashCode(cl);
2076 }
2077
2078 /**
2079 * Returns the identity hash code of the original referent.
2080 */
2081 @Override
2082 public int hashCode() {
2083 return hash;
2084 }
2085
2086 /**
2087 * Returns true if the given object is this identical
2088 * WeakClassKey instance, or, if this object's referent has not
2089 * been cleared, if the given object is another WeakClassKey
2090 * instance with the identical non-null referent as this one.
2091 */
2092 @Override
2093 public boolean equals(Object obj) {
2094 if (obj == this)
2095 return true;
2096
2097 if (obj instanceof WeakClassKey) {
2098 Object referent = get();
2099 return (referent != null) &&
2100 (referent == ((WeakClassKey) obj).get());
2101 } else {
2102 return false;
2103 }
2104 }
2105 }
2106
2107
2108 // The following three initially uninitialized fields are exclusively
2109 // managed by class java.util.concurrent.ThreadLocalRandom. These
2110 // fields are used to build the high-performance PRNGs in the
2111 // concurrent code, and we can not risk accidental false sharing.
2112 // Hence, the fields are isolated with @Contended.
2113
2114 /** The current seed for a ThreadLocalRandom */
2115 @jdk.internal.vm.annotation.Contended("tlr")
2116 long threadLocalRandomSeed;
2117
2118 /** Probe hash value; nonzero if threadLocalRandomSeed initialized */
2119 @jdk.internal.vm.annotation.Contended("tlr")
2120 int threadLocalRandomProbe;
2121
2122 /** Secondary seed isolated from public ThreadLocalRandom sequence */
2123 @jdk.internal.vm.annotation.Contended("tlr")
2124 int threadLocalRandomSecondarySeed;
2125
2126 /* Some private helper methods */
2127 private native void setPriority0(int newPriority);
2128 private native void stop0(Object o);
2129 private native void suspend0();
2130 private native void resume0();
2131 private native void interrupt0();
2132 private native void setNativeName(String name);
2133 }