1 /*
2 * Copyright (c) 1994, 2025, 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.reflect.Field;
30 import java.time.Duration;
31 import java.util.Map;
32 import java.util.HashMap;
33 import java.util.Objects;
34 import java.util.concurrent.Executor;
35 import java.util.concurrent.ThreadFactory;
36 import java.util.concurrent.StructureViolationException;
37 import java.util.concurrent.locks.LockSupport;
38 import jdk.internal.event.ThreadSleepEvent;
39 import jdk.internal.javac.Restricted;
40 import jdk.internal.misc.TerminatingThreadLocal;
41 import jdk.internal.misc.Unsafe;
42 import jdk.internal.misc.VM;
43 import jdk.internal.reflect.CallerSensitive;
44 import jdk.internal.reflect.Reflection;
45 import jdk.internal.vm.Continuation;
46 import jdk.internal.vm.ScopedValueContainer;
47 import jdk.internal.vm.StackableScope;
48 import jdk.internal.vm.ThreadContainer;
49 import jdk.internal.vm.annotation.ForceInline;
50 import jdk.internal.vm.annotation.Hidden;
51 import jdk.internal.vm.annotation.IntrinsicCandidate;
52 import jdk.internal.vm.annotation.Stable;
53 import sun.nio.ch.Interruptible;
54 import sun.nio.ch.NativeThread;
55
56 import static java.util.concurrent.TimeUnit.MILLISECONDS;
57 import static java.util.concurrent.TimeUnit.NANOSECONDS;
58
59 /**
60 * A <i>thread</i> is a thread of execution in a program. The Java
61 * virtual machine allows an application to have multiple threads of
62 * execution running concurrently.
63 *
64 * <p> {@code Thread} defines constructors and a {@link Builder} to create threads.
65 * {@linkplain #start() Starting} a thread schedules it to execute its {@link #run() run}
66 * method. The newly started thread executes concurrently with the thread that caused
67 * it to start.
68 *
69 * <p> A thread <i>terminates</i> if either its {@code run} method completes normally,
70 * or if its {@code run} method completes abruptly and the appropriate {@linkplain
71 * Thread.UncaughtExceptionHandler uncaught exception handler} completes normally or
72 * abruptly. With no code left to run, the thread has completed execution. The
73 * {@link #join() join} method can be used to wait for a thread to terminate.
74 *
75 * <p> Threads have a unique {@linkplain #threadId() identifier} and a {@linkplain
76 * #getName() name}. The identifier is generated when a {@code Thread} is created
77 * and cannot be changed. The thread name can be specified when creating a thread
78 * or can be {@linkplain #setName(String) changed} at a later time.
79 *
80 * <p> Threads support {@link ThreadLocal} variables. These are variables that are
81 * local to a thread, meaning a thread can have a copy of a variable that is set to
82 * a value that is independent of the value set by other threads. {@code Thread} also
83 * supports {@link InheritableThreadLocal} variables that are thread local variables
84 * that are inherited at thread creation time from the parent {@code Thread}.
85 * {@code Thread} supports a special inheritable thread local for the thread
86 * {@linkplain #getContextClassLoader() context-class-loader}.
87 *
88 * <h2><a id="platform-threads">Platform threads</a></h2>
89 * <p> {@code Thread} supports the creation of <i>platform threads</i> that are
90 * typically mapped 1:1 to kernel threads scheduled by the operating system.
91 * Platform threads will usually have a large stack and other resources that are
92 * maintained by the operating system. Platforms threads are suitable for executing
93 * all types of tasks but may be a limited resource.
94 *
95 * <p> Platform threads get an automatically generated thread name by default.
96 *
97 * <p> Platform threads are designated <i>daemon</i> or <i>non-daemon</i> threads.
98 * When the Java virtual machine starts up, there is usually one non-daemon
99 * thread (the thread that typically calls the application's {@code main} method).
100 * The <a href="Runtime.html#shutdown">shutdown sequence</a> begins when all started
101 * non-daemon threads have terminated. Unstarted non-daemon threads do not prevent
102 * the shutdown sequence from beginning.
103 *
104 * <p> In addition to the daemon status, platform threads have a {@linkplain
105 * #getPriority() thread priority} and are members of a {@linkplain ThreadGroup
106 * thread group}.
107 *
108 * <h2><a id="virtual-threads">Virtual threads</a></h2>
109 * <p> {@code Thread} also supports the creation of <i>virtual threads</i>.
110 * Virtual threads are typically <i>user-mode threads</i> scheduled by the Java
111 * runtime rather than the operating system. Virtual threads will typically require
112 * few resources and a single Java virtual machine may support millions of virtual
113 * threads. Virtual threads are suitable for executing tasks that spend most of
114 * the time blocked, often waiting for I/O operations to complete. Virtual threads
115 * are not intended for long running CPU intensive operations.
116 *
117 * <p> Virtual threads typically employ a small set of platform threads used as
118 * <em>carrier threads</em>. Locking and I/O operations are examples of operations
119 * where a carrier thread may be re-scheduled from one virtual thread to another.
120 * Code executing in a virtual thread is not aware of the underlying carrier thread.
121 * The {@linkplain Thread#currentThread()} method, used to obtain a reference
122 * to the <i>current thread</i>, will always return the {@code Thread} object
123 * for the virtual thread.
124 *
125 * <p> Virtual threads do not have a thread name by default. The {@link #getName()
126 * getName} method returns the empty string if a thread name is not set.
127 *
128 * <p> Virtual threads are daemon threads and so do not prevent the
129 * <a href="Runtime.html#shutdown">shutdown sequence</a> from beginning.
130 * Virtual threads have a fixed {@linkplain #getPriority() thread priority}
131 * that cannot be changed.
132 *
133 * <h2>Creating and starting threads</h2>
134 *
135 * <p> {@code Thread} defines public constructors for creating platform threads and
136 * the {@link #start() start} method to schedule threads to execute. {@code Thread}
137 * may be extended for customization and other advanced reasons although most
138 * applications should have little need to do this.
139 *
140 * <p> {@code Thread} defines a {@link Builder} API for creating and starting both
141 * platform and virtual threads. The following are examples that use the builder:
142 * {@snippet :
143 * Runnable runnable = ...
144 *
145 * // Start a daemon thread to run a task
146 * Thread thread = Thread.ofPlatform().daemon().start(runnable);
147 *
148 * // Create an unstarted thread with name "duke", its start() method
149 * // must be invoked to schedule it to execute.
150 * Thread thread = Thread.ofPlatform().name("duke").unstarted(runnable);
151 *
152 * // A ThreadFactory that creates daemon threads named "worker-0", "worker-1", ...
153 * ThreadFactory factory = Thread.ofPlatform().daemon().name("worker-", 0).factory();
154 *
155 * // Start a virtual thread to run a task
156 * Thread thread = Thread.ofVirtual().start(runnable);
157 *
158 * // A ThreadFactory that creates virtual threads
159 * ThreadFactory factory = Thread.ofVirtual().factory();
160 * }
161 *
162 * <h2><a id="inheritance">Inheritance when creating threads</a></h2>
163 * A {@code Thread} created with one of the public constructors inherits the daemon
164 * status and thread priority from the parent thread at the time that the child {@code
165 * Thread} is created. The {@linkplain ThreadGroup thread group} is also inherited when
166 * not provided to the constructor. When using a {@code Thread.Builder} to create a
167 * platform thread, the daemon status, thread priority, and thread group are inherited
168 * when not set on the builder. As with the constructors, inheriting from the parent
169 * thread is done when the child {@code Thread} is created.
170 *
171 * <p> A {@code Thread} inherits its initial values of {@linkplain InheritableThreadLocal
172 * inheritable-thread-local} variables (including the context class loader) from
173 * the parent thread values at the time that the child {@code Thread} is created.
174 * The 5-param {@linkplain Thread#Thread(ThreadGroup, Runnable, String, long, boolean)
175 * constructor} can be used to create a thread that does not inherit its initial
176 * values from the constructing thread. When using a {@code Thread.Builder}, the
177 * {@link Builder#inheritInheritableThreadLocals(boolean) inheritInheritableThreadLocals}
178 * method can be used to select if the initial values are inherited.
179 *
180 * <p> Unless otherwise specified, passing a {@code null} argument to a constructor
181 * or method in this class will cause a {@link NullPointerException} to be thrown.
182 *
183 * @implNote
184 * In the JDK Reference Implementation, the following system properties may be used to
185 * configure the built-in default virtual thread scheduler:
186 * <table class="striped">
187 * <caption style="display:none">System properties</caption>
188 * <thead>
189 * <tr>
190 * <th scope="col">System property</th>
191 * <th scope="col">Description</th>
192 * </tr>
193 * </thead>
194 * <tbody>
195 * <tr>
196 * <th scope="row">
197 * {@systemProperty jdk.virtualThreadScheduler.parallelism}
198 * </th>
199 * <td> The default scheduler's target parallelism. It defaults to the number of
200 * available processors. </td>
201 * </tr>
202 * <tr>
203 * <th scope="row">
204 * {@systemProperty jdk.virtualThreadScheduler.maxPoolSize}
205 * </th>
206 * <td> The maximum number of platform threads available to the default scheduler.
207 * It defaults to 256. </td>
208 * </tr>
209 * </tbody>
210 * </table>
211 *
212 * @since 1.0
213 */
214 public class Thread implements Runnable {
215 /* Make sure registerNatives is the first thing <clinit> does. */
216 private static native void registerNatives();
217 static {
218 registerNatives();
219 }
220
221 /*
222 * Reserved for exclusive use by the JVM. Cannot be moved to the FieldHolder
223 * as it needs to be set by the VM for JNI attaching threads, before executing
224 * the constructor that will create the FieldHolder. The historically named
225 * `eetop` holds the address of the underlying VM JavaThread, and is set to
226 * non-zero when the thread is started, and reset to zero when the thread terminates.
227 * A non-zero value indicates this thread isAlive().
228 */
229 private volatile long eetop;
230
231 // thread id
232 private final long tid;
233
234 // thread name
235 private volatile String name;
236
237 // interrupt status (read/written by VM)
238 volatile boolean interrupted;
239
240 // context ClassLoader
241 private volatile ClassLoader contextClassLoader;
242
243 // Additional fields for platform threads.
244 // All fields, except task and terminatingThreadLocals, are accessed directly by the VM.
245 private static class FieldHolder {
246 final ThreadGroup group;
247 final Runnable task;
248 final long stackSize;
249 volatile int priority;
250 volatile boolean daemon;
251 volatile int threadStatus;
252
253 // Native thread used for signalling, set lazily, read from any thread
254 volatile NativeThread nativeThread;
255
256 // This map is maintained by the ThreadLocal class
257 ThreadLocal.ThreadLocalMap terminatingThreadLocals;
258
259 FieldHolder(ThreadGroup group,
260 Runnable task,
261 long stackSize,
262 int priority,
263 boolean daemon) {
264 this.group = group;
265 this.task = task;
266 this.stackSize = stackSize;
267 this.priority = priority;
268 if (daemon)
269 this.daemon = true;
270 }
271 }
272 private final FieldHolder holder;
273
274 ThreadLocal.ThreadLocalMap terminatingThreadLocals() {
275 return holder.terminatingThreadLocals;
276 }
277
278 void setTerminatingThreadLocals(ThreadLocal.ThreadLocalMap map) {
279 holder.terminatingThreadLocals = map;
280 }
281
282 NativeThread nativeThread() {
283 return holder.nativeThread;
284 }
285
286 void setNativeThread(NativeThread nt) {
287 holder.nativeThread = nt;
288 }
289
290 /*
291 * ThreadLocal values pertaining to this thread. This map is maintained
292 * by the ThreadLocal class.
293 */
294 private ThreadLocal.ThreadLocalMap threadLocals;
295
296 ThreadLocal.ThreadLocalMap threadLocals() {
297 return threadLocals;
298 }
299
300 void setThreadLocals(ThreadLocal.ThreadLocalMap map) {
301 threadLocals = map;
302 }
303
304 /*
305 * InheritableThreadLocal values pertaining to this thread. This map is
306 * maintained by the InheritableThreadLocal class.
307 */
308 private ThreadLocal.ThreadLocalMap inheritableThreadLocals;
309
310 ThreadLocal.ThreadLocalMap inheritableThreadLocals() {
311 return inheritableThreadLocals;
312 }
313
314 void setInheritableThreadLocals(ThreadLocal.ThreadLocalMap map) {
315 inheritableThreadLocals = map;
316 }
317
318 /*
319 * Scoped value bindings are maintained by the ScopedValue class.
320 */
321 private Object scopedValueBindings;
322
323 // Special value to indicate this is a newly-created Thread
324 // Note that his must match the declaration in ScopedValue.
325 private static final Object NEW_THREAD_BINDINGS = Thread.class;
326
327 static Object scopedValueBindings() {
328 return currentThread().scopedValueBindings;
329 }
330
331 static void setScopedValueBindings(Object bindings) {
332 currentThread().scopedValueBindings = bindings;
333 }
334
335 /**
336 * Search the stack for the most recent scoped-value bindings.
337 */
338 @IntrinsicCandidate
339 static native Object findScopedValueBindings();
340
341 /**
342 * Inherit the scoped-value bindings from the given container.
343 * Invoked when starting a thread.
344 */
345 void inheritScopedValueBindings(ThreadContainer container) {
346 ScopedValueContainer.BindingsSnapshot snapshot;
347 if (container.owner() != null
348 && (snapshot = container.scopedValueBindings()) != null) {
349
350 // bindings established for running/calling an operation
351 Object bindings = snapshot.scopedValueBindings();
352 if (currentThread().scopedValueBindings != bindings) {
353 throw new StructureViolationException("Scoped value bindings have changed");
354 }
355
356 this.scopedValueBindings = bindings;
357 }
358 }
359
360 /*
361 * Lock object for thread interrupt.
362 */
363 final Object interruptLock = new Object();
364
365 /**
366 * The argument supplied to the current call to
367 * java.util.concurrent.locks.LockSupport.park.
368 * Set by (private) java.util.concurrent.locks.LockSupport.setBlocker
369 * Accessed using java.util.concurrent.locks.LockSupport.getBlocker
370 */
371 private volatile Object parkBlocker;
372
373 /* The object in which this thread is blocked in an interruptible I/O
374 * operation, if any. The blocker's interrupt method should be invoked
375 * after setting this thread's interrupt status.
376 */
377 private Interruptible nioBlocker;
378
379 Interruptible nioBlocker() {
380 //assert Thread.holdsLock(interruptLock);
381 return nioBlocker;
382 }
383
384 /* Set the blocker field; invoked via jdk.internal.access.SharedSecrets
385 * from java.nio code
386 */
387 void blockedOn(Interruptible b) {
388 //assert Thread.currentThread() == this;
389 synchronized (interruptLock) {
390 nioBlocker = b;
391 }
392 }
393
394 /**
395 * The minimum priority that a thread can have.
396 */
397 public static final int MIN_PRIORITY = 1;
398
399 /**
400 * The default priority that is assigned to a thread.
401 */
402 public static final int NORM_PRIORITY = 5;
403
404 /**
405 * The maximum priority that a thread can have.
406 */
407 public static final int MAX_PRIORITY = 10;
408
409 /*
410 * Current inner-most continuation.
411 */
412 private Continuation cont;
413
414 /**
415 * Returns the current continuation.
416 */
417 Continuation getContinuation() {
418 return cont;
419 }
420
421 /**
422 * Sets the current continuation.
423 */
424 void setContinuation(Continuation cont) {
425 this.cont = cont;
426 }
427
428 /**
429 * Returns the Thread object for the current platform thread. If the
430 * current thread is a virtual thread then this method returns the carrier.
431 */
432 @IntrinsicCandidate
433 static native Thread currentCarrierThread();
434
435 /**
436 * Returns the Thread object for the current thread.
437 * @return the current thread
438 */
439 @IntrinsicCandidate
440 public static native Thread currentThread();
441
442 /**
443 * Sets the Thread object to be returned by Thread.currentThread().
444 */
445 @IntrinsicCandidate
446 native void setCurrentThread(Thread thread);
447
448 // ScopedValue support:
449
450 @IntrinsicCandidate
451 static native Object[] scopedValueCache();
452
453 @IntrinsicCandidate
454 static native void setScopedValueCache(Object[] cache);
455
456 @IntrinsicCandidate
457 static native void ensureMaterializedForStackWalk(Object o);
458
459 /**
460 * A hint to the scheduler that the current thread is willing to yield
461 * its current use of a processor. The scheduler is free to ignore this
462 * hint.
463 *
464 * <p> Yield is a heuristic attempt to improve relative progression
465 * between threads that would otherwise over-utilise a CPU. Its use
466 * should be combined with detailed profiling and benchmarking to
467 * ensure that it actually has the desired effect.
468 *
469 * <p> It is rarely appropriate to use this method. It may be useful
470 * for debugging or testing purposes, where it may help to reproduce
471 * bugs due to race conditions. It may also be useful when designing
472 * concurrency control constructs such as the ones in the
473 * {@link java.util.concurrent.locks} package.
474 */
475 public static void yield() {
476 if (currentThread() instanceof VirtualThread vthread) {
477 vthread.tryYield();
478 } else {
479 yield0();
480 }
481 }
482
483 private static native void yield0();
484
485 /**
486 * Called before sleeping to create a jdk.ThreadSleep event.
487 */
488 private static ThreadSleepEvent beforeSleep(long nanos) {
489 try {
490 ThreadSleepEvent event = new ThreadSleepEvent();
491 if (event.isEnabled()) {
492 event.time = nanos;
493 event.begin();
494 return event;
495 }
496 } catch (OutOfMemoryError e) {
497 // ignore
498 }
499 return null;
500 }
501
502
503 /**
504 * Called after sleeping to commit the jdk.ThreadSleep event.
505 */
506 private static void afterSleep(ThreadSleepEvent event) {
507 if (event != null) {
508 try {
509 event.commit();
510 } catch (OutOfMemoryError e) {
511 // ignore
512 }
513 }
514 }
515
516 /**
517 * Sleep for the specified number of nanoseconds, subject to the precision
518 * and accuracy of system timers and schedulers.
519 */
520 private static void sleepNanos(long nanos) throws InterruptedException {
521 ThreadSleepEvent event = beforeSleep(nanos);
522 try {
523 if (currentThread() instanceof VirtualThread vthread) {
524 vthread.sleepNanos(nanos);
525 } else {
526 sleepNanos0(nanos);
527 }
528 } finally {
529 afterSleep(event);
530 }
531 }
532
533 private static native void sleepNanos0(long nanos) throws InterruptedException;
534
535 /**
536 * Causes the currently executing thread to sleep (temporarily cease
537 * execution) for the specified number of milliseconds, subject to
538 * the precision and accuracy of system timers and schedulers. The thread
539 * does not lose ownership of any monitors.
540 *
541 * @param millis
542 * the length of time to sleep in milliseconds
543 *
544 * @throws IllegalArgumentException
545 * if the value of {@code millis} is negative
546 *
547 * @throws InterruptedException
548 * if any thread has interrupted the current thread. The
549 * <i>interrupted status</i> of the current thread is
550 * cleared when this exception is thrown.
551 */
552 public static void sleep(long millis) throws InterruptedException {
553 if (millis < 0) {
554 throw new IllegalArgumentException("timeout value is negative");
555 }
556 long nanos = MILLISECONDS.toNanos(millis);
557 sleepNanos(nanos);
558 }
559
560 /**
561 * Causes the currently executing thread to sleep (temporarily cease
562 * execution) for the specified number of milliseconds plus the specified
563 * number of nanoseconds, subject to the precision and accuracy of system
564 * timers and schedulers. The thread does not lose ownership of any
565 * monitors.
566 *
567 * @param millis
568 * the length of time to sleep in milliseconds
569 *
570 * @param nanos
571 * {@code 0-999999} additional nanoseconds to sleep
572 *
573 * @throws IllegalArgumentException
574 * if the value of {@code millis} is negative, or the value of
575 * {@code nanos} is not in the range {@code 0-999999}
576 *
577 * @throws InterruptedException
578 * if any thread has interrupted the current thread. The
579 * <i>interrupted status</i> of the current thread is
580 * cleared when this exception is thrown.
581 */
582 public static void sleep(long millis, int nanos) throws InterruptedException {
583 if (millis < 0) {
584 throw new IllegalArgumentException("timeout value is negative");
585 }
586
587 if (nanos < 0 || nanos > 999999) {
588 throw new IllegalArgumentException("nanosecond timeout value out of range");
589 }
590
591 // total sleep time, in nanoseconds
592 long totalNanos = MILLISECONDS.toNanos(millis);
593 totalNanos += Math.min(Long.MAX_VALUE - totalNanos, nanos);
594 sleepNanos(totalNanos);
595 }
596
597 /**
598 * Causes the currently executing thread to sleep (temporarily cease
599 * execution) for the specified duration, subject to the precision and
600 * accuracy of system timers and schedulers. This method is a no-op if
601 * the duration is {@linkplain Duration#isNegative() negative}.
602 *
603 * @param duration
604 * the duration to sleep
605 *
606 * @throws InterruptedException
607 * if the current thread is interrupted while sleeping. The
608 * <i>interrupted status</i> of the current thread is
609 * cleared when this exception is thrown.
610 *
611 * @since 19
612 */
613 public static void sleep(Duration duration) throws InterruptedException {
614 long nanos = NANOSECONDS.convert(duration); // MAX_VALUE if > 292 years
615 if (nanos < 0) {
616 return;
617 }
618 sleepNanos(nanos);
619 }
620
621 /**
622 * Indicates that the caller is momentarily unable to progress, until the
623 * occurrence of one or more actions on the part of other activities. By
624 * invoking this method within each iteration of a spin-wait loop construct,
625 * the calling thread indicates to the runtime that it is busy-waiting.
626 * The runtime may take action to improve the performance of invoking
627 * spin-wait loop constructions.
628 *
629 * @apiNote
630 * As an example consider a method in a class that spins in a loop until
631 * some flag is set outside of that method. A call to the {@code onSpinWait}
632 * method should be placed inside the spin loop.
633 * {@snippet :
634 * class EventHandler {
635 * volatile boolean eventNotificationNotReceived;
636 * void waitForEventAndHandleIt() {
637 * while ( eventNotificationNotReceived ) {
638 * Thread.onSpinWait();
639 * }
640 * readAndProcessEvent();
641 * }
642 *
643 * void readAndProcessEvent() {
644 * // Read event from some source and process it
645 * . . .
646 * }
647 * }
648 * }
649 * <p>
650 * The code above would remain correct even if the {@code onSpinWait}
651 * method was not called at all. However on some architectures the Java
652 * Virtual Machine may issue the processor instructions to address such
653 * code patterns in a more beneficial way.
654 *
655 * @since 9
656 */
657 @IntrinsicCandidate
658 public static void onSpinWait() {}
659
660 /**
661 * Characteristic value signifying that initial values for {@link
662 * InheritableThreadLocal inheritable-thread-locals} are not inherited from
663 * the constructing thread.
664 * See Thread initialization.
665 */
666 static final int NO_INHERIT_THREAD_LOCALS = 1 << 2;
667
668 /**
669 * Thread identifier assigned to the primordial thread.
670 */
671 static final long PRIMORDIAL_TID = 3;
672
673 /**
674 * Helper class to generate thread identifiers. The identifiers start at
675 * {@link Thread#PRIMORDIAL_TID} +1 as this class cannot be used during
676 * early startup to generate the identifier for the primordial thread. The
677 * counter is off-heap and shared with the VM to allow it to assign thread
678 * identifiers to non-Java threads.
679 * See Thread initialization.
680 */
681 private static class ThreadIdentifiers {
682 private static final Unsafe U;
683 private static final long NEXT_TID_OFFSET;
684 static {
685 U = Unsafe.getUnsafe();
686 NEXT_TID_OFFSET = Thread.getNextThreadIdOffset();
687 }
688 static long next() {
689 return U.getAndAddLong(null, NEXT_TID_OFFSET, 1);
690 }
691 }
692
693 /**
694 * Initializes a platform Thread.
695 *
696 * @param g the Thread group, can be null
697 * @param name the name of the new Thread
698 * @param characteristics thread characteristics
699 * @param task the object whose run() method gets called
700 * @param stackSize the desired stack size for the new thread, or
701 * zero to indicate that this parameter is to be ignored.
702 */
703 Thread(ThreadGroup g, String name, int characteristics, Runnable task, long stackSize) {
704 Thread parent = currentThread();
705 boolean attached = (parent == this); // primordial or JNI attached
706
707 if (attached) {
708 if (g == null) {
709 throw new InternalError("group cannot be null when attaching");
710 }
711 this.holder = new FieldHolder(g, task, stackSize, NORM_PRIORITY, false);
712 } else {
713 if (g == null) {
714 // default to current thread's group
715 g = parent.getThreadGroup();
716 }
717 int priority = Math.min(parent.getPriority(), g.getMaxPriority());
718 this.holder = new FieldHolder(g, task, stackSize, priority, parent.isDaemon());
719 }
720
721 if (attached && VM.initLevel() < 1) {
722 this.tid = PRIMORDIAL_TID; // primordial thread
723 } else {
724 this.tid = ThreadIdentifiers.next();
725 }
726
727 this.name = (name != null) ? name : genThreadName();
728
729 // thread locals
730 if (!attached) {
731 if ((characteristics & NO_INHERIT_THREAD_LOCALS) == 0) {
732 ThreadLocal.ThreadLocalMap parentMap = parent.inheritableThreadLocals;
733 if (parentMap != null && parentMap.size() > 0) {
734 this.inheritableThreadLocals = ThreadLocal.createInheritedMap(parentMap);
735 }
736 if (VM.isBooted()) {
737 this.contextClassLoader = parent.getContextClassLoader();
738 }
739 } else if (VM.isBooted()) {
740 // default CCL to the system class loader when not inheriting
741 this.contextClassLoader = ClassLoader.getSystemClassLoader();
742 }
743 }
744
745 // special value to indicate this is a newly-created Thread
746 // Note that his must match the declaration in ScopedValue.
747 this.scopedValueBindings = NEW_THREAD_BINDINGS;
748 }
749
750 /**
751 * Initializes a virtual Thread.
752 *
753 * @param name thread name, can be null
754 * @param characteristics thread characteristics
755 * @param bound true when bound to an OS thread
756 */
757 Thread(String name, int characteristics, boolean bound) {
758 this.tid = ThreadIdentifiers.next();
759 this.name = (name != null) ? name : "";
760
761 // thread locals
762 if ((characteristics & NO_INHERIT_THREAD_LOCALS) == 0) {
763 Thread parent = currentThread();
764 ThreadLocal.ThreadLocalMap parentMap = parent.inheritableThreadLocals;
765 if (parentMap != null && parentMap.size() > 0) {
766 this.inheritableThreadLocals = ThreadLocal.createInheritedMap(parentMap);
767 }
768 this.contextClassLoader = parent.getContextClassLoader();
769 } else {
770 // default CCL to the system class loader when not inheriting
771 this.contextClassLoader = ClassLoader.getSystemClassLoader();
772 }
773
774 // special value to indicate this is a newly-created Thread
775 this.scopedValueBindings = NEW_THREAD_BINDINGS;
776
777 // create a FieldHolder object, needed when bound to an OS thread
778 if (bound) {
779 ThreadGroup g = Constants.VTHREAD_GROUP;
780 int pri = NORM_PRIORITY;
781 this.holder = new FieldHolder(g, null, -1, pri, true);
782 } else {
783 this.holder = null;
784 }
785 }
786
787 /**
788 * Virtual thread scheduler.
789 *
790 * @apiNote The following example creates a virtual thread scheduler that uses a small
791 * set of platform threads.
792 * {@snippet lang=java :
793 * ExecutorService pool = Executors.newFixedThreadPool(4);
794 * VirtualThreadScheduler scheduler = (vthread, task) -> {
795 * pool.submit(() -> {
796 * Thread carrier = Thread.currentThread();
797 *
798 * // runs the virtual thread task
799 * task.run();
800 *
801 * assert Thread.currentThread() == carrier;
802 * });
803 * };
804 * }
805 *
806 * <p> Unless otherwise specified, passing a null argument to a method in
807 * this interface causes a {@code NullPointerException} to be thrown.
808 *
809 * @see Builder.OfVirtual#scheduler(VirtualThreadScheduler)
810 * @since 99
811 */
812 @FunctionalInterface
813 public interface VirtualThreadScheduler {
814 /**
815 * Continue execution of given virtual thread by executing the given task on
816 * a platform thread.
817 *
818 * @param vthread the virtual thread
819 * @param task the task to execute
820 */
821 void execute(Thread vthread, Runnable task);
822
823 /**
824 * {@return a virtual thread scheduler that delegates tasks to the given executor}
825 * @param executor the executor
826 */
827 static VirtualThreadScheduler adapt(Executor executor) {
828 Objects.requireNonNull(executor);
829 return (_, task) -> executor.execute(task);
830 }
831
832 /**
833 * {@return the virtual thread scheduler for the current virtual thread}
834 * @throws UnsupportedOperationException if the current thread is not a virtual
835 * thread or scheduling virtual threads to a user-provided scheduler is not
836 * supported by this VM
837 */
838 @CallerSensitive
839 @Restricted
840 static VirtualThreadScheduler current() {
841 Class<?> caller = Reflection.getCallerClass();
842 caller.getModule().ensureNativeAccess(VirtualThreadScheduler.class,
843 "current",
844 caller,
845 false);
846 if (Thread.currentThread() instanceof VirtualThread vthread) {
847 return vthread.scheduler(false);
848 } else {
849 throw new UnsupportedOperationException();
850 }
851 }
852 }
853
854 /**
855 * Returns a builder for creating a platform {@code Thread} or {@code ThreadFactory}
856 * that creates platform threads.
857 *
858 * @apiNote The following are examples using the builder:
859 * {@snippet :
860 * // Start a daemon thread to run a task
861 * Thread thread = Thread.ofPlatform().daemon().start(runnable);
862 *
863 * // Create an unstarted thread with name "duke", its start() method
864 * // must be invoked to schedule it to execute.
865 * Thread thread = Thread.ofPlatform().name("duke").unstarted(runnable);
866 *
867 * // A ThreadFactory that creates daemon threads named "worker-0", "worker-1", ...
868 * ThreadFactory factory = Thread.ofPlatform().daemon().name("worker-", 0).factory();
869 * }
870 *
871 * @return A builder for creating {@code Thread} or {@code ThreadFactory} objects.
872 * @since 21
873 */
874 public static Builder.OfPlatform ofPlatform() {
875 return new ThreadBuilders.PlatformThreadBuilder();
876 }
877
878 /**
879 * Returns a builder for creating a virtual {@code Thread} or {@code ThreadFactory}
880 * that creates virtual threads.
881 *
882 * @apiNote The following are examples using the builder:
883 * {@snippet :
884 * // Start a virtual thread to run a task.
885 * Thread thread = Thread.ofVirtual().start(runnable);
886 *
887 * // A ThreadFactory that creates virtual threads
888 * ThreadFactory factory = Thread.ofVirtual().factory();
889 * }
890 *
891 * @return A builder for creating {@code Thread} or {@code ThreadFactory} objects.
892 * @since 21
893 */
894 public static Builder.OfVirtual ofVirtual() {
895 return new ThreadBuilders.VirtualThreadBuilder();
896 }
897
898 /**
899 * A builder for {@link Thread} and {@link ThreadFactory} objects.
900 *
901 * <p> {@code Builder} defines methods to set {@code Thread} properties such
902 * as the thread {@link #name(String) name}. This includes properties that would
903 * otherwise be <a href="Thread.html#inheritance">inherited</a>. Once set, a
904 * {@code Thread} or {@code ThreadFactory} is created with the following methods:
905 *
906 * <ul>
907 * <li> The {@linkplain #unstarted(Runnable) unstarted} method creates a new
908 * <em>unstarted</em> {@code Thread} to run a task. The {@code Thread}'s
909 * {@link Thread#start() start} method must be invoked to schedule the
910 * thread to execute.
911 * <li> The {@linkplain #start(Runnable) start} method creates a new {@code
912 * Thread} to run a task and schedules the thread to execute.
913 * <li> The {@linkplain #factory() factory} method creates a {@code ThreadFactory}.
914 * </ul>
915 *
916 * <p> A {@code Thread.Builder} is not thread safe. The {@code ThreadFactory}
917 * returned by the builder's {@code factory()} method is thread safe.
918 *
919 * <p> Unless otherwise specified, passing a null argument to a method in
920 * this interface causes a {@code NullPointerException} to be thrown.
921 *
922 * @see Thread#ofPlatform()
923 * @see Thread#ofVirtual()
924 * @since 21
925 */
926 public sealed interface Builder
927 permits Builder.OfPlatform, Builder.OfVirtual {
928
929 /**
930 * Sets the thread name.
931 * @param name thread name
932 * @return this builder
933 */
934 Builder name(String name);
935
936 /**
937 * Sets the thread name to be the concatenation of a string prefix and
938 * the string representation of a counter value. The counter's initial
939 * value is {@code start}. It is incremented after a {@code Thread} is
940 * created with this builder so that the next thread is named with
941 * the new counter value. A {@code ThreadFactory} created with this
942 * builder is seeded with the current value of the counter. The {@code
943 * ThreadFactory} increments its copy of the counter after {@link
944 * ThreadFactory#newThread(Runnable) newThread} is used to create a
945 * {@code Thread}.
946 *
947 * @apiNote
948 * The following example creates a builder that is invoked twice to start
949 * two threads named "{@code worker-0}" and "{@code worker-1}".
950 * {@snippet :
951 * Thread.Builder builder = Thread.ofPlatform().name("worker-", 0);
952 * Thread t1 = builder.start(task1); // name "worker-0"
953 * Thread t2 = builder.start(task2); // name "worker-1"
954 * }
955 *
956 * @param prefix thread name prefix
957 * @param start the starting value of the counter
958 * @return this builder
959 * @throws IllegalArgumentException if start is negative
960 */
961 Builder name(String prefix, long start);
962
963 /**
964 * Sets whether the thread inherits the initial values of {@linkplain
965 * InheritableThreadLocal inheritable-thread-local} variables from the
966 * constructing thread. The default is to inherit.
967 *
968 * @param inherit {@code true} to inherit, {@code false} to not inherit
969 * @return this builder
970 */
971 Builder inheritInheritableThreadLocals(boolean inherit);
972
973 /**
974 * Sets the uncaught exception handler.
975 * @param ueh uncaught exception handler
976 * @return this builder
977 */
978 Builder uncaughtExceptionHandler(UncaughtExceptionHandler ueh);
979
980 /**
981 * Creates a new {@code Thread} from the current state of the builder to
982 * run the given task. The {@code Thread}'s {@link Thread#start() start}
983 * method must be invoked to schedule the thread to execute.
984 *
985 * @param task the object to run when the thread executes
986 * @return a new unstarted Thread
987 *
988 * @see <a href="Thread.html#inheritance">Inheritance when creating threads</a>
989 */
990 Thread unstarted(Runnable task);
991
992 /**
993 * Creates a new {@code Thread} from the current state of the builder and
994 * schedules it to execute.
995 *
996 * @param task the object to run when the thread executes
997 * @return a new started Thread
998 *
999 * @see <a href="Thread.html#inheritance">Inheritance when creating threads</a>
1000 */
1001 Thread start(Runnable task);
1002
1003 /**
1004 * Returns a {@code ThreadFactory} to create threads from the current
1005 * state of the builder. The returned thread factory is safe for use by
1006 * multiple concurrent threads.
1007 *
1008 * @return a thread factory to create threads
1009 */
1010 ThreadFactory factory();
1011
1012 /**
1013 * A builder for creating a platform {@link Thread} or {@link ThreadFactory}
1014 * that creates platform threads.
1015 *
1016 * <p> Unless otherwise specified, passing a null argument to a method in
1017 * this interface causes a {@code NullPointerException} to be thrown.
1018 *
1019 * @see Thread#ofPlatform()
1020 * @since 21
1021 */
1022 sealed interface OfPlatform extends Builder
1023 permits ThreadBuilders.PlatformThreadBuilder {
1024
1025 @Override OfPlatform name(String name);
1026
1027 /**
1028 * @throws IllegalArgumentException {@inheritDoc}
1029 */
1030 @Override OfPlatform name(String prefix, long start);
1031
1032 @Override OfPlatform inheritInheritableThreadLocals(boolean inherit);
1033 @Override OfPlatform uncaughtExceptionHandler(UncaughtExceptionHandler ueh);
1034
1035 /**
1036 * Sets the thread group.
1037 * @param group the thread group
1038 * @return this builder
1039 */
1040 OfPlatform group(ThreadGroup group);
1041
1042 /**
1043 * Sets the daemon status.
1044 * @param on {@code true} to create daemon threads
1045 * @return this builder
1046 */
1047 OfPlatform daemon(boolean on);
1048
1049 /**
1050 * Sets the daemon status to {@code true}.
1051 * @implSpec The default implementation invokes {@linkplain #daemon(boolean)} with
1052 * a value of {@code true}.
1053 * @return this builder
1054 */
1055 default OfPlatform daemon() {
1056 return daemon(true);
1057 }
1058
1059 /**
1060 * Sets the thread priority.
1061 * @param priority priority
1062 * @return this builder
1063 * @throws IllegalArgumentException if the priority is less than
1064 * {@link Thread#MIN_PRIORITY} or greater than {@link Thread#MAX_PRIORITY}
1065 */
1066 OfPlatform priority(int priority);
1067
1068 /**
1069 * Sets the desired stack size.
1070 *
1071 * <p> The stack size is the approximate number of bytes of address space
1072 * that the Java virtual machine is to allocate for the thread's stack. The
1073 * effect is highly platform dependent and the Java virtual machine is free
1074 * to treat the {@code stackSize} parameter as a "suggestion". If the value
1075 * is unreasonably low for the platform then a platform specific minimum
1076 * may be used. If the value is unreasonably high then a platform specific
1077 * maximum may be used. A value of zero is always ignored.
1078 *
1079 * @param stackSize the desired stack size
1080 * @return this builder
1081 * @throws IllegalArgumentException if the stack size is negative
1082 */
1083 OfPlatform stackSize(long stackSize);
1084 }
1085
1086 /**
1087 * A builder for creating a virtual {@link Thread} or {@link ThreadFactory}
1088 * that creates virtual threads.
1089 *
1090 * <p> Unless otherwise specified, passing a null argument to a method in
1091 * this interface causes a {@code NullPointerException} to be thrown.
1092 *
1093 * @see Thread#ofVirtual()
1094 * @since 21
1095 */
1096 sealed interface OfVirtual extends Builder
1097 permits ThreadBuilders.VirtualThreadBuilder {
1098
1099 @Override OfVirtual name(String name);
1100
1101 /**
1102 * @throws IllegalArgumentException {@inheritDoc}
1103 */
1104 @Override OfVirtual name(String prefix, long start);
1105
1106 @Override OfVirtual inheritInheritableThreadLocals(boolean inherit);
1107 @Override OfVirtual uncaughtExceptionHandler(UncaughtExceptionHandler ueh);
1108
1109 /**
1110 * Sets the scheduler.
1111 *
1112 * The thread will be scheduled by the Java virtual machine with the given
1113 * scheduler. The scheduler's {@link VirtualThreadScheduler#execute(Thread, Runnable)}
1114 * method may be invoked in the context of a virtual thread. The scheduler
1115 * must arrange to execute the {@code Runnable}'s {@code run} method on a
1116 * platform thread. Attempting to execute the run method in a virtual thread
1117 * causes {@link WrongThreadException} to be thrown.
1118 *
1119 * The {@code execute} method may be invoked at sensitive times (e.g. when
1120 * unparking a thread) so care should be taken to not directly execute the
1121 * task on the <em>current thread</em>.
1122 *
1123 * @param scheduler the scheduler
1124 * @return this builder
1125 * @throws UnsupportedOperationException if scheduling virtual threads to a
1126 * user-provided scheduler is not supported by this VM
1127 *
1128 * @since 99
1129 */
1130 @CallerSensitive
1131 @Restricted
1132 OfVirtual scheduler(VirtualThreadScheduler scheduler);
1133 }
1134 }
1135
1136 /**
1137 * Throws CloneNotSupportedException as a Thread can not be meaningfully
1138 * cloned. Construct a new Thread instead.
1139 *
1140 * @throws CloneNotSupportedException
1141 * always
1142 */
1143 @Override
1144 protected Object clone() throws CloneNotSupportedException {
1145 throw new CloneNotSupportedException();
1146 }
1147
1148 /**
1149 * Helper class for auto-numbering platform threads. The numbers start at
1150 * 0 and are separate from the thread identifier for historical reasons.
1151 */
1152 private static class ThreadNumbering {
1153 private static final Unsafe U;
1154 private static final Object NEXT_BASE;
1155 private static final long NEXT_OFFSET;
1156 static {
1157 U = Unsafe.getUnsafe();
1158 try {
1159 Field nextField = ThreadNumbering.class.getDeclaredField("next");
1160 NEXT_BASE = U.staticFieldBase(nextField);
1161 NEXT_OFFSET = U.staticFieldOffset(nextField);
1162 } catch (NoSuchFieldException e) {
1163 throw new ExceptionInInitializerError(e);
1164 }
1165 }
1166 private static volatile int next;
1167 static int next() {
1168 return U.getAndAddInt(NEXT_BASE, NEXT_OFFSET, 1);
1169 }
1170 }
1171
1172 /**
1173 * Generates a thread name of the form {@code Thread-<n>}.
1174 */
1175 static String genThreadName() {
1176 return "Thread-" + ThreadNumbering.next();
1177 }
1178
1179 /**
1180 * Throws NullPointerException if the name is null. Avoids use of
1181 * Objects.requireNonNull in early startup.
1182 */
1183 private static String checkName(String name) {
1184 if (name == null)
1185 throw new NullPointerException("'name' is null");
1186 return name;
1187 }
1188
1189 /**
1190 * Initializes a new platform {@code Thread}. This constructor has the same
1191 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
1192 * {@code (null, null, gname)}, where {@code gname} is a newly generated
1193 * name. Automatically generated names are of the form
1194 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
1195 *
1196 * <p> This constructor is only useful when extending {@code Thread} to
1197 * override the {@link #run()} method.
1198 *
1199 * @see <a href="#inheritance">Inheritance when creating threads</a>
1200 */
1201 public Thread() {
1202 this(null, null, 0, null, 0);
1203 }
1204
1205 /**
1206 * Initializes a new platform {@code Thread}. This constructor has the same
1207 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
1208 * {@code (null, task, gname)}, where {@code gname} is a newly generated
1209 * name. Automatically generated names are of the form
1210 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
1211 *
1212 * <p> For a non-null task, invoking this constructor directly is equivalent to:
1213 * <pre>{@code Thread.ofPlatform().unstarted(task); }</pre>
1214 *
1215 * @param task
1216 * the object whose {@code run} method is invoked when this thread
1217 * is started. If {@code null}, this classes {@code run} method does
1218 * nothing.
1219 *
1220 * @see <a href="#inheritance">Inheritance when creating threads</a>
1221 */
1222 public Thread(Runnable task) {
1223 this(null, null, 0, task, 0);
1224 }
1225
1226 /**
1227 * Initializes a new platform {@code Thread}. This constructor has the same
1228 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
1229 * {@code (group, task, gname)}, where {@code gname} is a newly generated
1230 * name. Automatically generated names are of the form
1231 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
1232 *
1233 * <p> For a non-null group and task, invoking this constructor directly is
1234 * equivalent to:
1235 * <pre>{@code Thread.ofPlatform().group(group).unstarted(task); }</pre>
1236 *
1237 * @param group
1238 * the thread group. If {@code null} the group
1239 * is set to the current thread's thread group.
1240 *
1241 * @param task
1242 * the object whose {@code run} method is invoked when this thread
1243 * is started. If {@code null}, this thread's run method is invoked.
1244 *
1245 * @see <a href="#inheritance">Inheritance when creating threads</a>
1246 */
1247 public Thread(ThreadGroup group, Runnable task) {
1248 this(group, null, 0, task, 0);
1249 }
1250
1251 /**
1252 * Initializes a new platform {@code Thread}. This constructor has the same
1253 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
1254 * {@code (null, null, name)}.
1255 *
1256 * <p> This constructor is only useful when extending {@code Thread} to
1257 * override the {@link #run()} method.
1258 *
1259 * @param name
1260 * the name of the new thread
1261 *
1262 * @see <a href="#inheritance">Inheritance when creating threads</a>
1263 */
1264 public Thread(String name) {
1265 this(null, checkName(name), 0, null, 0);
1266 }
1267
1268 /**
1269 * Initializes a new platform {@code Thread}. This constructor has the same
1270 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
1271 * {@code (group, null, name)}.
1272 *
1273 * <p> This constructor is only useful when extending {@code Thread} to
1274 * override the {@link #run()} method.
1275 *
1276 * @param group
1277 * the thread group. If {@code null}, the group
1278 * is set to the current thread's thread group.
1279 *
1280 * @param name
1281 * the name of the new thread
1282 *
1283 * @see <a href="#inheritance">Inheritance when creating threads</a>
1284 */
1285 public Thread(ThreadGroup group, String name) {
1286 this(group, checkName(name), 0, null, 0);
1287 }
1288
1289 /**
1290 * Initializes a new platform {@code Thread}. This constructor has the same
1291 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
1292 * {@code (null, task, name)}.
1293 *
1294 * <p> For a non-null task and name, invoking this constructor directly is
1295 * equivalent to:
1296 * <pre>{@code Thread.ofPlatform().name(name).unstarted(task); }</pre>
1297 *
1298 * @param task
1299 * the object whose {@code run} method is invoked when this thread
1300 * is started. If {@code null}, this thread's run method is invoked.
1301 *
1302 * @param name
1303 * the name of the new thread
1304 *
1305 * @see <a href="#inheritance">Inheritance when creating threads</a>
1306 */
1307 public Thread(Runnable task, String name) {
1308 this(null, checkName(name), 0, task, 0);
1309 }
1310
1311 /**
1312 * Initializes a new platform {@code Thread} so that it has {@code task}
1313 * as its run object, has the specified {@code name} as its name,
1314 * and belongs to the thread group referred to by {@code group}.
1315 *
1316 * <p>The priority of the newly created thread is the smaller of
1317 * priority of the thread creating it and the maximum permitted
1318 * priority of the thread group. The method {@linkplain #setPriority
1319 * setPriority} may be used to change the priority to a new value.
1320 *
1321 * <p>The newly created thread is initially marked as being a daemon
1322 * thread if and only if the thread creating it is currently marked
1323 * as a daemon thread. The method {@linkplain #setDaemon setDaemon}
1324 * may be used to change whether or not a thread is a daemon.
1325 *
1326 * <p>For a non-null group, task, and name, invoking this constructor directly
1327 * is equivalent to:
1328 * <pre>{@code Thread.ofPlatform().group(group).name(name).unstarted(task); }</pre>
1329 *
1330 * @param group
1331 * the thread group. If {@code null}, the group
1332 * is set to the current thread's thread group.
1333 *
1334 * @param task
1335 * the object whose {@code run} method is invoked when this thread
1336 * is started. If {@code null}, this thread's run method is invoked.
1337 *
1338 * @param name
1339 * the name of the new thread
1340 *
1341 * @see <a href="#inheritance">Inheritance when creating threads</a>
1342 */
1343 public Thread(ThreadGroup group, Runnable task, String name) {
1344 this(group, checkName(name), 0, task, 0);
1345 }
1346
1347 /**
1348 * Initializes a new platform {@code Thread} so that it has {@code task}
1349 * as its run object, has the specified {@code name} as its name,
1350 * and belongs to the thread group referred to by {@code group}, and has
1351 * the specified <i>stack size</i>.
1352 *
1353 * <p>This constructor is identical to {@link
1354 * #Thread(ThreadGroup,Runnable,String)} with the exception of the fact
1355 * that it allows the thread stack size to be specified. The stack size
1356 * is the approximate number of bytes of address space that the virtual
1357 * machine is to allocate for this thread's stack. <b>The effect of the
1358 * {@code stackSize} parameter, if any, is highly platform dependent.</b>
1359 *
1360 * <p>On some platforms, specifying a higher value for the
1361 * {@code stackSize} parameter may allow a thread to achieve greater
1362 * recursion depth before throwing a {@link StackOverflowError}.
1363 * Similarly, specifying a lower value may allow a greater number of
1364 * threads to exist concurrently without throwing an {@link
1365 * OutOfMemoryError} (or other internal error). The details of
1366 * the relationship between the value of the {@code stackSize} parameter
1367 * and the maximum recursion depth and concurrency level are
1368 * platform-dependent. <b>On some platforms, the value of the
1369 * {@code stackSize} parameter may have no effect whatsoever.</b>
1370 *
1371 * <p>The virtual machine is free to treat the {@code stackSize}
1372 * parameter as a suggestion. If the specified value is unreasonably low
1373 * for the platform, the virtual machine may instead use some
1374 * platform-specific minimum value; if the specified value is unreasonably
1375 * high, the virtual machine may instead use some platform-specific
1376 * maximum. Likewise, the virtual machine is free to round the specified
1377 * value up or down as it sees fit (or to ignore it completely).
1378 *
1379 * <p>Specifying a value of zero for the {@code stackSize} parameter will
1380 * cause this constructor to behave exactly like the
1381 * {@code Thread(ThreadGroup, Runnable, String)} constructor.
1382 *
1383 * <p><i>Due to the platform-dependent nature of the behavior of this
1384 * constructor, extreme care should be exercised in its use.
1385 * The thread stack size necessary to perform a given computation will
1386 * likely vary from one JRE implementation to another. In light of this
1387 * variation, careful tuning of the stack size parameter may be required,
1388 * and the tuning may need to be repeated for each JRE implementation on
1389 * which an application is to run.</i>
1390 *
1391 * <p>Implementation note: Java platform implementers are encouraged to
1392 * document their implementation's behavior with respect to the
1393 * {@code stackSize} parameter.
1394 *
1395 * <p>For a non-null group, task, and name, invoking this constructor directly
1396 * is equivalent to:
1397 * <pre>{@code Thread.ofPlatform().group(group).name(name).stackSize(stackSize).unstarted(task); }</pre>
1398 *
1399 * @param group
1400 * the thread group. If {@code null}, the group
1401 * is set to the current thread's thread group.
1402 *
1403 * @param task
1404 * the object whose {@code run} method is invoked when this thread
1405 * is started. If {@code null}, this thread's run method is invoked.
1406 *
1407 * @param name
1408 * the name of the new thread
1409 *
1410 * @param stackSize
1411 * the desired stack size for the new thread, or zero to indicate
1412 * that this parameter is to be ignored.
1413 *
1414 * @since 1.4
1415 * @see <a href="#inheritance">Inheritance when creating threads</a>
1416 */
1417 public Thread(ThreadGroup group, Runnable task, String name, long stackSize) {
1418 this(group, checkName(name), 0, task, stackSize);
1419 }
1420
1421 /**
1422 * Initializes a new platform {@code Thread} so that it has {@code task}
1423 * as its run object, has the specified {@code name} as its name,
1424 * belongs to the thread group referred to by {@code group}, has
1425 * the specified {@code stackSize}, and inherits initial values for
1426 * {@linkplain InheritableThreadLocal inheritable thread-local} variables
1427 * if {@code inheritThreadLocals} is {@code true}.
1428 *
1429 * <p> This constructor is identical to {@link
1430 * #Thread(ThreadGroup,Runnable,String,long)} with the added ability to
1431 * suppress, or not, the inheriting of initial values for inheritable
1432 * thread-local variables from the constructing thread. This allows for
1433 * finer grain control over inheritable thread-locals. Care must be taken
1434 * when passing a value of {@code false} for {@code inheritThreadLocals},
1435 * as it may lead to unexpected behavior if the new thread executes code
1436 * that expects a specific thread-local value to be inherited.
1437 *
1438 * <p> Specifying a value of {@code true} for the {@code inheritThreadLocals}
1439 * parameter will cause this constructor to behave exactly like the
1440 * {@code Thread(ThreadGroup, Runnable, String, long)} constructor.
1441 *
1442 * <p> For a non-null group, task, and name, invoking this constructor directly
1443 * is equivalent to:
1444 * <pre>{@code Thread.ofPlatform()
1445 * .group(group)
1446 * .name(name)
1447 * .stackSize(stackSize)
1448 * .inheritInheritableThreadLocals(inheritInheritableThreadLocals)
1449 * .unstarted(task); }</pre>
1450 *
1451 * @param group
1452 * the thread group. If {@code null}, the group
1453 * is set to the current thread's thread group.
1454 *
1455 * @param task
1456 * the object whose {@code run} method is invoked when this thread
1457 * is started. If {@code null}, this thread's run method is invoked.
1458 *
1459 * @param name
1460 * the name of the new thread
1461 *
1462 * @param stackSize
1463 * the desired stack size for the new thread, or zero to indicate
1464 * that this parameter is to be ignored
1465 *
1466 * @param inheritInheritableThreadLocals
1467 * if {@code true}, inherit initial values for inheritable
1468 * thread-locals from the constructing thread, otherwise no initial
1469 * values are inherited
1470 *
1471 * @since 9
1472 * @see <a href="#inheritance">Inheritance when creating threads</a>
1473 */
1474 public Thread(ThreadGroup group, Runnable task, String name,
1475 long stackSize, boolean inheritInheritableThreadLocals) {
1476 this(group, checkName(name),
1477 (inheritInheritableThreadLocals ? 0 : NO_INHERIT_THREAD_LOCALS),
1478 task, stackSize);
1479 }
1480
1481 /**
1482 * Creates a virtual thread to execute a task and schedules it to execute.
1483 * The thread is scheduled to the default virtual thread scheduler.
1484 *
1485 * <p> This method is equivalent to:
1486 * <pre>{@code Thread.ofVirtual().start(task); }</pre>
1487 *
1488 * @param task the object to run when the thread executes
1489 * @return a new, and started, virtual thread
1490 * @see <a href="#inheritance">Inheritance when creating threads</a>
1491 * @since 21
1492 */
1493 public static Thread startVirtualThread(Runnable task) {
1494 Objects.requireNonNull(task);
1495 var thread = ThreadBuilders.newVirtualThread(null, null, 0, task);
1496 thread.start();
1497 return thread;
1498 }
1499
1500 /**
1501 * Returns {@code true} if this thread is a virtual thread. A virtual thread
1502 * is scheduled by the Java virtual machine rather than the operating system.
1503 *
1504 * @return {@code true} if this thread is a virtual thread
1505 *
1506 * @since 21
1507 */
1508 public final boolean isVirtual() {
1509 return (this instanceof BaseVirtualThread);
1510 }
1511
1512 /**
1513 * Schedules this thread to begin execution. The thread will execute
1514 * independently of the current thread.
1515 *
1516 * <p> A thread can be started at most once. In particular, a thread can not
1517 * be restarted after it has terminated.
1518 *
1519 * @throws IllegalThreadStateException if the thread was already started
1520 */
1521 public void start() {
1522 synchronized (this) {
1523 // zero status corresponds to state "NEW".
1524 if (holder.threadStatus != 0)
1525 throw new IllegalThreadStateException();
1526 start0();
1527 }
1528 }
1529
1530 /**
1531 * Schedules this thread to begin execution in the given thread container.
1532 * @throws IllegalStateException if the container is shutdown or closed
1533 * @throws IllegalThreadStateException if the thread has already been started
1534 */
1535 void start(ThreadContainer container) {
1536 synchronized (this) {
1537 // zero status corresponds to state "NEW".
1538 if (holder.threadStatus != 0)
1539 throw new IllegalThreadStateException();
1540
1541 // bind thread to container
1542 if (this.container != null)
1543 throw new IllegalThreadStateException();
1544 setThreadContainer(container);
1545
1546 // start thread
1547 boolean started = false;
1548 container.add(this); // may throw
1549 try {
1550 // scoped values may be inherited
1551 inheritScopedValueBindings(container);
1552
1553 start0();
1554 started = true;
1555 } finally {
1556 if (!started) {
1557 container.remove(this);
1558 }
1559 }
1560 }
1561 }
1562
1563 private native void start0();
1564
1565 /**
1566 * This method is run by the thread when it executes. Subclasses of {@code
1567 * Thread} may override this method.
1568 *
1569 * <p> This method is not intended to be invoked directly. If this thread is a
1570 * platform thread created with a {@link Runnable} task then invoking this method
1571 * will invoke the task's {@code run} method. If this thread is a virtual thread
1572 * then invoking this method directly does nothing.
1573 *
1574 * @implSpec The default implementation executes the {@link Runnable} task that
1575 * the {@code Thread} was created with. If the thread was created without a task
1576 * then this method does nothing.
1577 */
1578 @Override
1579 public void run() {
1580 Runnable task = holder.task;
1581 if (task != null) {
1582 Object bindings = scopedValueBindings();
1583 runWith(bindings, task);
1584 }
1585 }
1586
1587 /**
1588 * The VM recognizes this method as special, so any changes to the
1589 * name or signature require corresponding changes in
1590 * JVM_FindScopedValueBindings().
1591 */
1592 @Hidden
1593 @ForceInline
1594 final void runWith(Object bindings, Runnable op) {
1595 ensureMaterializedForStackWalk(bindings);
1596 op.run();
1597 Reference.reachabilityFence(bindings);
1598 }
1599
1600 /**
1601 * Null out reference after Thread termination.
1602 */
1603 void clearReferences() {
1604 threadLocals = null;
1605 inheritableThreadLocals = null;
1606 if (uncaughtExceptionHandler != null)
1607 uncaughtExceptionHandler = null;
1608 if (nioBlocker != null)
1609 nioBlocker = null;
1610 }
1611
1612 /**
1613 * This method is called by the VM to give a Thread
1614 * a chance to clean up before it actually exits.
1615 */
1616 private void exit() {
1617 try {
1618 // pop any remaining scopes from the stack, this may block
1619 if (headStackableScopes != null) {
1620 StackableScope.popAll();
1621 }
1622 } finally {
1623 // notify container that thread is exiting
1624 ThreadContainer container = threadContainer();
1625 if (container != null) {
1626 container.remove(this);
1627 }
1628 }
1629
1630 try {
1631 if (terminatingThreadLocals() != null) {
1632 TerminatingThreadLocal.threadTerminated();
1633 }
1634 } finally {
1635 clearReferences();
1636 }
1637 }
1638
1639 /**
1640 * Throws {@code UnsupportedOperationException}.
1641 *
1642 * @throws UnsupportedOperationException always
1643 *
1644 * @deprecated This method was originally specified to "stop" a victim
1645 * thread by causing the victim thread to throw a {@link ThreadDeath}.
1646 * It was inherently unsafe. Stopping a thread caused it to unlock
1647 * all of the monitors that it had locked (as a natural consequence
1648 * of the {@code ThreadDeath} exception propagating up the stack). If
1649 * any of the objects previously protected by these monitors were in
1650 * an inconsistent state, the damaged objects became visible to
1651 * other threads, potentially resulting in arbitrary behavior.
1652 * Usages of {@code stop} should be replaced by code that simply
1653 * modifies some variable to indicate that the target thread should
1654 * stop running. The target thread should check this variable
1655 * regularly, and return from its run method in an orderly fashion
1656 * if the variable indicates that it is to stop running. If the
1657 * target thread waits for long periods (on a condition variable,
1658 * for example), the {@code interrupt} method should be used to
1659 * interrupt the wait.
1660 * For more information, see
1661 * <a href="{@docRoot}/java.base/java/lang/doc-files/threadPrimitiveDeprecation.html">Why
1662 * is Thread.stop deprecated and the ability to stop a thread removed?</a>.
1663 */
1664 @Deprecated(since="1.2", forRemoval=true)
1665 public final void stop() {
1666 throw new UnsupportedOperationException();
1667 }
1668
1669 /**
1670 * Interrupts this thread.
1671 *
1672 * <p> If this thread is blocked in an invocation of the {@link
1673 * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
1674 * Object#wait(long, int) wait(long, int)} methods of the {@link Object}
1675 * class, or of the {@link #join()}, {@link #join(long)}, {@link
1676 * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)}
1677 * methods of this class, then its interrupt status will be cleared and it
1678 * will receive an {@link InterruptedException}.
1679 *
1680 * <p> If this thread is blocked in an I/O operation upon an {@link
1681 * java.nio.channels.InterruptibleChannel InterruptibleChannel}
1682 * then the channel will be closed, the thread's interrupt
1683 * status will be set, and the thread will receive a {@link
1684 * java.nio.channels.ClosedByInterruptException}.
1685 *
1686 * <p> If this thread is blocked in a {@link java.nio.channels.Selector}
1687 * then the thread's interrupt status will be set and it will return
1688 * immediately from the selection operation, possibly with a non-zero
1689 * value, just as if the selector's {@link
1690 * java.nio.channels.Selector#wakeup wakeup} method were invoked.
1691 *
1692 * <p> If none of the previous conditions hold then this thread's interrupt
1693 * status will be set. </p>
1694 *
1695 * <p> Interrupting a thread that is not alive need not have any effect.
1696 *
1697 * @implNote In the JDK Reference Implementation, interruption of a thread
1698 * that is not alive still records that the interrupt request was made and
1699 * will report it via {@link #interrupted()} and {@link #isInterrupted()}.
1700 */
1701 public void interrupt() {
1702 // Setting the interrupt status must be done before reading nioBlocker.
1703 interrupted = true;
1704 interrupt0(); // inform VM of interrupt
1705
1706 // thread may be blocked in an I/O operation
1707 if (this != Thread.currentThread()) {
1708 Interruptible blocker;
1709 synchronized (interruptLock) {
1710 blocker = nioBlocker;
1711 if (blocker != null) {
1712 blocker.interrupt(this);
1713 }
1714 }
1715 if (blocker != null) {
1716 blocker.postInterrupt();
1717 }
1718 }
1719 }
1720
1721 /**
1722 * Tests whether the current thread has been interrupted. The
1723 * <i>interrupted status</i> of the thread is cleared by this method. In
1724 * other words, if this method were to be called twice in succession, the
1725 * second call would return false (unless the current thread were
1726 * interrupted again, after the first call had cleared its interrupted
1727 * status and before the second call had examined it).
1728 *
1729 * @return {@code true} if the current thread has been interrupted;
1730 * {@code false} otherwise.
1731 * @see #isInterrupted()
1732 */
1733 public static boolean interrupted() {
1734 return currentThread().getAndClearInterrupt();
1735 }
1736
1737 /**
1738 * Tests whether this thread has been interrupted. The <i>interrupted
1739 * status</i> of the thread is unaffected by this method.
1740 *
1741 * @return {@code true} if this thread has been interrupted;
1742 * {@code false} otherwise.
1743 * @see #interrupted()
1744 */
1745 public boolean isInterrupted() {
1746 return interrupted;
1747 }
1748
1749 final void setInterrupt() {
1750 // assert Thread.currentCarrierThread() == this;
1751 if (!interrupted) {
1752 interrupted = true;
1753 interrupt0(); // inform VM of interrupt
1754 }
1755 }
1756
1757 final void clearInterrupt() {
1758 // assert Thread.currentCarrierThread() == this;
1759 if (interrupted) {
1760 interrupted = false;
1761 clearInterruptEvent();
1762 }
1763 }
1764
1765 boolean getAndClearInterrupt() {
1766 boolean oldValue = interrupted;
1767 // We may have been interrupted the moment after we read the field,
1768 // so only clear the field if we saw that it was set and will return
1769 // true; otherwise we could lose an interrupt.
1770 if (oldValue) {
1771 interrupted = false;
1772 clearInterruptEvent();
1773 }
1774 return oldValue;
1775 }
1776
1777 /**
1778 * Tests if this thread is alive. A thread is alive if it has
1779 * been started and has not yet terminated.
1780 *
1781 * @return {@code true} if this thread is alive;
1782 * {@code false} otherwise.
1783 */
1784 public final boolean isAlive() {
1785 return alive();
1786 }
1787
1788 /**
1789 * Returns true if this thread is alive.
1790 * This method is non-final so it can be overridden.
1791 */
1792 boolean alive() {
1793 return eetop != 0;
1794 }
1795
1796 /**
1797 * Changes the priority of this thread.
1798 *
1799 * For platform threads, the priority is set to the smaller of the specified
1800 * {@code newPriority} and the maximum permitted priority of the thread's
1801 * {@linkplain ThreadGroup thread group}.
1802 *
1803 * The priority of a virtual thread is always {@link Thread#NORM_PRIORITY}
1804 * and {@code newPriority} is ignored.
1805 *
1806 * @param newPriority the new thread priority
1807 * @throws IllegalArgumentException if the priority is not in the
1808 * range {@code MIN_PRIORITY} to {@code MAX_PRIORITY}.
1809 * @see #setPriority(int)
1810 * @see ThreadGroup#getMaxPriority()
1811 */
1812 public final void setPriority(int newPriority) {
1813 if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
1814 throw new IllegalArgumentException();
1815 }
1816 if (!isVirtual()) {
1817 priority(newPriority);
1818 }
1819 }
1820
1821 void priority(int newPriority) {
1822 ThreadGroup g = holder.group;
1823 if (g != null) {
1824 int maxPriority = g.getMaxPriority();
1825 if (newPriority > maxPriority) {
1826 newPriority = maxPriority;
1827 }
1828 setPriority0(holder.priority = newPriority);
1829 }
1830 }
1831
1832 /**
1833 * Returns this thread's priority.
1834 *
1835 * <p> The priority of a virtual thread is always {@link Thread#NORM_PRIORITY}.
1836 *
1837 * @return this thread's priority.
1838 * @see #setPriority
1839 */
1840 public final int getPriority() {
1841 if (isVirtual()) {
1842 return Thread.NORM_PRIORITY;
1843 } else {
1844 return holder.priority;
1845 }
1846 }
1847
1848 /**
1849 * Changes the name of this thread to be equal to the argument {@code name}.
1850 *
1851 * @implNote In the JDK Reference Implementation, if this thread is the
1852 * current thread, and it's a platform thread that was not attached to the
1853 * VM with the Java Native Interface
1854 * <a href="{@docRoot}/../specs/jni/invocation.html#attachcurrentthread">
1855 * AttachCurrentThread</a> function, then this method will set the operating
1856 * system thread name. This may be useful for debugging and troubleshooting
1857 * purposes.
1858 *
1859 * @param name the new name for this thread.
1860 *
1861 * @spec jni/index.html Java Native Interface Specification
1862 * @see #getName
1863 */
1864 public final synchronized void setName(String name) {
1865 if (name == null) {
1866 throw new NullPointerException("name cannot be null");
1867 }
1868 this.name = name;
1869 if (!isVirtual() && Thread.currentThread() == this) {
1870 setNativeName(name);
1871 }
1872 }
1873
1874 /**
1875 * Returns this thread's name.
1876 *
1877 * @return this thread's name.
1878 * @see #setName(String)
1879 */
1880 public final String getName() {
1881 return name;
1882 }
1883
1884 /**
1885 * Returns the thread's thread group or {@code null} if the thread has
1886 * terminated.
1887 *
1888 * <p> The thread group returned for a virtual thread is the special
1889 * <a href="ThreadGroup.html#virtualthreadgroup"><em>ThreadGroup for
1890 * virtual threads</em></a>.
1891 *
1892 * @return this thread's thread group or {@code null}
1893 */
1894 public final ThreadGroup getThreadGroup() {
1895 if (isTerminated()) {
1896 return null;
1897 } else {
1898 return isVirtual() ? virtualThreadGroup() : holder.group;
1899 }
1900 }
1901
1902 /**
1903 * Returns an estimate of the number of {@linkplain #isAlive() live}
1904 * platform threads in the current thread's thread group and its subgroups.
1905 * Virtual threads are not included in the estimate.
1906 *
1907 * <p> The value returned is only an estimate because the number of
1908 * threads may change dynamically while this method traverses internal
1909 * data structures, and might be affected by the presence of certain
1910 * system threads. This method is intended primarily for debugging
1911 * and monitoring purposes.
1912 *
1913 * @return an estimate of the number of live platform threads in the
1914 * current thread's thread group and in any other thread group
1915 * that has the current thread's thread group as an ancestor
1916 */
1917 public static int activeCount() {
1918 return currentThread().getThreadGroup().activeCount();
1919 }
1920
1921 /**
1922 * Copies into the specified array every {@linkplain #isAlive() live}
1923 * platform thread in the current thread's thread group and its subgroups.
1924 * This method simply invokes the {@link java.lang.ThreadGroup#enumerate(Thread[])}
1925 * method of the current thread's thread group. Virtual threads are
1926 * not enumerated by this method.
1927 *
1928 * <p> An application might use the {@linkplain #activeCount activeCount}
1929 * method to get an estimate of how big the array should be, however
1930 * <i>if the array is too short to hold all the threads, the extra threads
1931 * are silently ignored.</i> If it is critical to obtain every live
1932 * thread in the current thread's thread group and its subgroups, the
1933 * invoker should verify that the returned int value is strictly less
1934 * than the length of {@code tarray}.
1935 *
1936 * <p> Due to the inherent race condition in this method, it is recommended
1937 * that the method only be used for debugging and monitoring purposes.
1938 *
1939 * @param tarray
1940 * an array into which to put the list of threads
1941 *
1942 * @return the number of threads put into the array
1943 */
1944 public static int enumerate(Thread[] tarray) {
1945 return currentThread().getThreadGroup().enumerate(tarray);
1946 }
1947
1948 /**
1949 * Waits at most {@code millis} milliseconds for this thread to terminate.
1950 * A timeout of {@code 0} means to wait forever.
1951 * This method returns immediately, without waiting, if the thread has not
1952 * been {@link #start() started}.
1953 *
1954 * @implNote
1955 * For platform threads, the implementation uses a loop of {@code this.wait}
1956 * calls conditioned on {@code this.isAlive}. As a thread terminates the
1957 * {@code this.notifyAll} method is invoked. It is recommended that
1958 * applications not use {@code wait}, {@code notify}, or
1959 * {@code notifyAll} on {@code Thread} instances.
1960 *
1961 * @param millis
1962 * the time to wait in milliseconds
1963 *
1964 * @throws IllegalArgumentException
1965 * if the value of {@code millis} is negative
1966 *
1967 * @throws InterruptedException
1968 * if any thread has interrupted the current thread. The
1969 * <i>interrupted status</i> of the current thread is
1970 * cleared when this exception is thrown.
1971 */
1972 public final void join(long millis) throws InterruptedException {
1973 if (millis < 0)
1974 throw new IllegalArgumentException("timeout value is negative");
1975
1976 if (this instanceof VirtualThread vthread) {
1977 if (isAlive()) {
1978 long nanos = MILLISECONDS.toNanos(millis);
1979 vthread.joinNanos(nanos);
1980 }
1981 return;
1982 }
1983
1984 synchronized (this) {
1985 if (millis > 0) {
1986 if (isAlive()) {
1987 final long startTime = System.nanoTime();
1988 long delay = millis;
1989 do {
1990 wait(delay);
1991 } while (isAlive() && (delay = millis -
1992 NANOSECONDS.toMillis(System.nanoTime() - startTime)) > 0);
1993 }
1994 } else {
1995 while (isAlive()) {
1996 wait(0);
1997 }
1998 }
1999 }
2000 }
2001
2002 /**
2003 * Waits at most {@code millis} milliseconds plus
2004 * {@code nanos} nanoseconds for this thread to terminate.
2005 * If both arguments are {@code 0}, it means to wait forever.
2006 * This method returns immediately, without waiting, if the thread has not
2007 * been {@link #start() started}.
2008 *
2009 * @implNote
2010 * For platform threads, the implementation uses a loop of {@code this.wait}
2011 * calls conditioned on {@code this.isAlive}. As a thread terminates the
2012 * {@code this.notifyAll} method is invoked. It is recommended that
2013 * applications not use {@code wait}, {@code notify}, or
2014 * {@code notifyAll} on {@code Thread} instances.
2015 *
2016 * @param millis
2017 * the time to wait in milliseconds
2018 *
2019 * @param nanos
2020 * {@code 0-999999} additional nanoseconds to wait
2021 *
2022 * @throws IllegalArgumentException
2023 * if the value of {@code millis} is negative, or the value
2024 * of {@code nanos} is not in the range {@code 0-999999}
2025 *
2026 * @throws InterruptedException
2027 * if any thread has interrupted the current thread. The
2028 * <i>interrupted status</i> of the current thread is
2029 * cleared when this exception is thrown.
2030 */
2031 public final void join(long millis, int nanos) throws InterruptedException {
2032 if (millis < 0) {
2033 throw new IllegalArgumentException("timeout value is negative");
2034 }
2035
2036 if (nanos < 0 || nanos > 999999) {
2037 throw new IllegalArgumentException("nanosecond timeout value out of range");
2038 }
2039
2040 if (this instanceof VirtualThread vthread) {
2041 if (isAlive()) {
2042 // convert arguments to a total in nanoseconds
2043 long totalNanos = MILLISECONDS.toNanos(millis);
2044 totalNanos += Math.min(Long.MAX_VALUE - totalNanos, nanos);
2045 vthread.joinNanos(totalNanos);
2046 }
2047 return;
2048 }
2049
2050 if (nanos > 0 && millis < Long.MAX_VALUE) {
2051 millis++;
2052 }
2053 join(millis);
2054 }
2055
2056 /**
2057 * Waits for this thread to terminate.
2058 *
2059 * <p> An invocation of this method behaves in exactly the same
2060 * way as the invocation
2061 *
2062 * <blockquote>
2063 * {@linkplain #join(long) join}{@code (0)}
2064 * </blockquote>
2065 *
2066 * @throws InterruptedException
2067 * if any thread has interrupted the current thread. The
2068 * <i>interrupted status</i> of the current thread is
2069 * cleared when this exception is thrown.
2070 */
2071 public final void join() throws InterruptedException {
2072 join(0);
2073 }
2074
2075 /**
2076 * Waits for this thread to terminate for up to the given waiting duration.
2077 *
2078 * <p> This method does not wait if the duration to wait is less than or
2079 * equal to zero. In this case, the method just tests if the thread has
2080 * terminated.
2081 *
2082 * @param duration
2083 * the maximum duration to wait
2084 *
2085 * @return {@code true} if the thread has terminated, {@code false} if the
2086 * thread has not terminated
2087 *
2088 * @throws InterruptedException
2089 * if the current thread is interrupted while waiting.
2090 * The <i>interrupted status</i> of the current thread is cleared
2091 * when this exception is thrown.
2092 *
2093 * @throws IllegalThreadStateException
2094 * if this thread has not been started.
2095 *
2096 * @since 19
2097 */
2098 public final boolean join(Duration duration) throws InterruptedException {
2099 long nanos = NANOSECONDS.convert(duration); // MAX_VALUE if > 292 years
2100
2101 Thread.State state = threadState();
2102 if (state == State.NEW)
2103 throw new IllegalThreadStateException("Thread not started");
2104 if (state == State.TERMINATED)
2105 return true;
2106 if (nanos <= 0)
2107 return false;
2108
2109 if (this instanceof VirtualThread vthread) {
2110 return vthread.joinNanos(nanos);
2111 }
2112
2113 // convert to milliseconds
2114 long millis = MILLISECONDS.convert(nanos, NANOSECONDS);
2115 if (nanos > NANOSECONDS.convert(millis, MILLISECONDS)) {
2116 millis += 1L;
2117 }
2118 join(millis);
2119 return isTerminated();
2120 }
2121
2122 /**
2123 * Prints a stack trace of the current thread to the standard error stream.
2124 * This method is useful for debugging.
2125 */
2126 public static void dumpStack() {
2127 new Exception("Stack trace").printStackTrace();
2128 }
2129
2130 /**
2131 * Marks this thread as either a <i>daemon</i> or <i>non-daemon</i> thread.
2132 * The <a href="Runtime.html#shutdown">shutdown sequence</a> begins when all
2133 * started non-daemon threads have terminated.
2134 *
2135 * <p> The daemon status of a virtual thread is always {@code true} and cannot be
2136 * changed by this method to {@code false}.
2137 *
2138 * <p> This method must be invoked before the thread is started. The behavior
2139 * of this method when the thread has terminated is not specified.
2140 *
2141 * @param on
2142 * if {@code true}, marks this thread as a daemon thread
2143 *
2144 * @throws IllegalArgumentException
2145 * if this is a virtual thread and {@code on} is false
2146 * @throws IllegalThreadStateException
2147 * if this thread is {@linkplain #isAlive alive}
2148 */
2149 public final void setDaemon(boolean on) {
2150 if (isVirtual() && !on)
2151 throw new IllegalArgumentException("'false' not legal for virtual threads");
2152 if (isAlive())
2153 throw new IllegalThreadStateException();
2154 if (!isVirtual())
2155 daemon(on);
2156 }
2157
2158 void daemon(boolean on) {
2159 holder.daemon = on;
2160 }
2161
2162 /**
2163 * Tests if this thread is a daemon thread.
2164 * The daemon status of a virtual thread is always {@code true}.
2165 *
2166 * @return {@code true} if this thread is a daemon thread;
2167 * {@code false} otherwise.
2168 * @see #setDaemon(boolean)
2169 */
2170 public final boolean isDaemon() {
2171 if (isVirtual()) {
2172 return true;
2173 } else {
2174 return holder.daemon;
2175 }
2176 }
2177
2178 /**
2179 * Does nothing.
2180 *
2181 * @deprecated This method originally determined if the currently running
2182 * thread had permission to modify this thread. This method was only useful
2183 * in conjunction with {@linkplain SecurityManager the Security Manager},
2184 * which is no longer supported. There is no replacement for the Security
2185 * Manager or this method.
2186 */
2187 @Deprecated(since="17", forRemoval=true)
2188 public final void checkAccess() { }
2189
2190 /**
2191 * Returns a string representation of this thread. The string representation
2192 * will usually include the thread's {@linkplain #threadId() identifier} and
2193 * name. The default implementation for platform threads includes the thread's
2194 * identifier, name, priority, and the name of the thread group.
2195 *
2196 * @return a string representation of this thread.
2197 */
2198 public String toString() {
2199 StringBuilder sb = new StringBuilder("Thread[#");
2200 sb.append(threadId());
2201 sb.append(",");
2202 sb.append(getName());
2203 sb.append(",");
2204 sb.append(getPriority());
2205 sb.append(",");
2206 ThreadGroup group = getThreadGroup();
2207 if (group != null)
2208 sb.append(group.getName());
2209 sb.append("]");
2210 return sb.toString();
2211 }
2212
2213 /**
2214 * Returns the context {@code ClassLoader} for this thread.
2215 * The context {@code ClassLoader} may be set by the creator of the thread
2216 * for use by code running in this thread when loading classes and resources.
2217 * If not {@linkplain #setContextClassLoader set}, the default is to inherit
2218 * the context class loader from the parent thread.
2219 *
2220 * <p> The context {@code ClassLoader} of the primordial thread is typically
2221 * set to the class loader used to load the application.
2222 *
2223 * @return the context {@code ClassLoader} for this thread, or {@code null}
2224 * indicating the system class loader (or, failing that, the
2225 * bootstrap class loader)
2226 *
2227 * @since 1.2
2228 */
2229 public ClassLoader getContextClassLoader() {
2230 return contextClassLoader;
2231 }
2232
2233 /**
2234 * Sets the context {@code ClassLoader} for this thread.
2235 *
2236 * <p> The context {@code ClassLoader} may be set by the creator of the thread
2237 * for use by code running in this thread when loading classes and resources.
2238 *
2239 * @param cl
2240 * the context ClassLoader for this Thread, or null indicating the
2241 * system class loader (or, failing that, the bootstrap class loader)
2242 *
2243 * @since 1.2
2244 */
2245 public void setContextClassLoader(ClassLoader cl) {
2246 contextClassLoader = cl;
2247 }
2248
2249 /**
2250 * Returns {@code true} if and only if the current thread holds the
2251 * monitor lock on the specified object.
2252 *
2253 * <p>This method is designed to allow a program to assert that
2254 * the current thread already holds a specified lock:
2255 * <pre>
2256 * assert Thread.holdsLock(obj);
2257 * </pre>
2258 *
2259 * @param obj the object on which to test lock ownership
2260 * @return {@code true} if the current thread holds the monitor lock on
2261 * the specified object.
2262 * @since 1.4
2263 */
2264 public static native boolean holdsLock(Object obj);
2265
2266 private static final StackTraceElement[] EMPTY_STACK_TRACE
2267 = new StackTraceElement[0];
2268
2269 /**
2270 * Returns an array of stack trace elements representing the stack dump
2271 * of this thread. This method will return a zero-length array if
2272 * this thread has not started, has started but has not yet been
2273 * scheduled to run by the system, or has terminated.
2274 * If the returned array is of non-zero length then the first element of
2275 * the array represents the top of the stack, which is the most recent
2276 * method invocation in the sequence. The last element of the array
2277 * represents the bottom of the stack, which is the least recent method
2278 * invocation in the sequence.
2279 *
2280 * <p>Some virtual machines may, under some circumstances, omit one
2281 * or more stack frames from the stack trace. In the extreme case,
2282 * a virtual machine that has no stack trace information concerning
2283 * this thread is permitted to return a zero-length array from this
2284 * method.
2285 *
2286 * @return an array of {@code StackTraceElement},
2287 * each represents one stack frame.
2288 *
2289 * @see Throwable#getStackTrace
2290 * @since 1.5
2291 */
2292 public StackTraceElement[] getStackTrace() {
2293 if (this != Thread.currentThread()) {
2294 // optimization so we do not call into the vm for threads that
2295 // have not yet started or have terminated
2296 if (!isAlive()) {
2297 return EMPTY_STACK_TRACE;
2298 }
2299 StackTraceElement[] stackTrace = asyncGetStackTrace();
2300 return (stackTrace != null) ? stackTrace : EMPTY_STACK_TRACE;
2301 } else {
2302 return (new Exception()).getStackTrace();
2303 }
2304 }
2305
2306 /**
2307 * Returns an array of stack trace elements representing the stack dump of
2308 * this thread. Returns null if the stack trace cannot be obtained. In
2309 * the default implementation, null is returned if the thread is a virtual
2310 * thread that is not mounted or the thread is a platform thread that has
2311 * terminated.
2312 */
2313 StackTraceElement[] asyncGetStackTrace() {
2314 Object stackTrace = getStackTrace0();
2315 if (stackTrace == null) {
2316 return null;
2317 }
2318 StackTraceElement[] stes = (StackTraceElement[]) stackTrace;
2319 if (stes.length == 0) {
2320 return null;
2321 } else {
2322 return StackTraceElement.of(stes);
2323 }
2324 }
2325
2326 private native Object getStackTrace0();
2327
2328 /**
2329 * Returns a map of stack traces for all live platform threads. The map
2330 * does not include virtual threads.
2331 * The map keys are threads and each map value is an array of
2332 * {@code StackTraceElement} that represents the stack dump
2333 * of the corresponding {@code Thread}.
2334 * The returned stack traces are in the format specified for
2335 * the {@link #getStackTrace getStackTrace} method.
2336 *
2337 * <p>The threads may be executing while this method is called.
2338 * The stack trace of each thread only represents a snapshot and
2339 * each stack trace may be obtained at different time. A zero-length
2340 * array will be returned in the map value if the virtual machine has
2341 * no stack trace information about a thread.
2342 *
2343 * @return a {@code Map} from {@code Thread} to an array of
2344 * {@code StackTraceElement} that represents the stack trace of
2345 * the corresponding thread.
2346 *
2347 * @see #getStackTrace
2348 * @see Throwable#getStackTrace
2349 *
2350 * @since 1.5
2351 */
2352 public static Map<Thread, StackTraceElement[]> getAllStackTraces() {
2353 // Get a snapshot of the list of all threads
2354 Thread[] threads = getThreads();
2355 StackTraceElement[][] traces = dumpThreads(threads);
2356 Map<Thread, StackTraceElement[]> m = HashMap.newHashMap(threads.length);
2357 for (int i = 0; i < threads.length; i++) {
2358 StackTraceElement[] stackTrace = traces[i];
2359 if (stackTrace != null) {
2360 m.put(threads[i], stackTrace);
2361 }
2362 // else terminated so we don't put it in the map
2363 }
2364 return m;
2365 }
2366
2367 /**
2368 * Return an array of all live threads.
2369 */
2370 static Thread[] getAllThreads() {
2371 return getThreads();
2372 }
2373
2374 private static native StackTraceElement[][] dumpThreads(Thread[] threads);
2375 private static native Thread[] getThreads();
2376
2377 /**
2378 * Returns the identifier of this Thread. The thread ID is a positive
2379 * {@code long} number generated when this thread was created.
2380 * The thread ID is unique and remains unchanged during its lifetime.
2381 *
2382 * @return this thread's ID
2383 *
2384 * @deprecated This method is not final and may be overridden to return a
2385 * value that is not the thread ID. Use {@link #threadId()} instead.
2386 *
2387 * @since 1.5
2388 */
2389 @Deprecated(since="19")
2390 public long getId() {
2391 return threadId();
2392 }
2393
2394 /**
2395 * Returns the identifier of this Thread. The thread ID is a positive
2396 * {@code long} number generated when this thread was created.
2397 * The thread ID is unique and remains unchanged during its lifetime.
2398 *
2399 * @return this thread's ID
2400 * @since 19
2401 */
2402 public final long threadId() {
2403 return tid;
2404 }
2405
2406 /**
2407 * A thread state. A thread can be in one of the following states:
2408 * <ul>
2409 * <li>{@link #NEW}<br>
2410 * A thread that has not yet started is in this state.
2411 * </li>
2412 * <li>{@link #RUNNABLE}<br>
2413 * A thread executing in the Java virtual machine is in this state.
2414 * </li>
2415 * <li>{@link #BLOCKED}<br>
2416 * A thread that is blocked waiting for a monitor lock
2417 * is in this state.
2418 * </li>
2419 * <li>{@link #WAITING}<br>
2420 * A thread that is waiting indefinitely for another thread to
2421 * perform a particular action is in this state.
2422 * </li>
2423 * <li>{@link #TIMED_WAITING}<br>
2424 * A thread that is waiting for another thread to perform an action
2425 * for up to a specified waiting time is in this state.
2426 * </li>
2427 * <li>{@link #TERMINATED}<br>
2428 * A thread that has exited is in this state.
2429 * </li>
2430 * </ul>
2431 *
2432 * <p>
2433 * A thread can be in only one state at a given point in time.
2434 * These states are virtual machine states which do not reflect
2435 * any operating system thread states.
2436 *
2437 * @since 1.5
2438 * @see #getState
2439 */
2440 public enum State {
2441 /**
2442 * Thread state for a thread which has not yet started.
2443 */
2444 NEW,
2445
2446 /**
2447 * Thread state for a runnable thread. A thread in the runnable
2448 * state is executing in the Java virtual machine but it may
2449 * be waiting for other resources from the operating system
2450 * such as processor.
2451 */
2452 RUNNABLE,
2453
2454 /**
2455 * Thread state for a thread blocked waiting for a monitor lock.
2456 * A thread in the blocked state is waiting for a monitor lock
2457 * to enter a synchronized block/method or
2458 * reenter a synchronized block/method after calling
2459 * {@link Object#wait() Object.wait}.
2460 */
2461 BLOCKED,
2462
2463 /**
2464 * Thread state for a waiting thread.
2465 * A thread is in the waiting state due to calling one of the
2466 * following methods:
2467 * <ul>
2468 * <li>{@link Object#wait() Object.wait} with no timeout</li>
2469 * <li>{@link #join() Thread.join} with no timeout</li>
2470 * <li>{@link LockSupport#park() LockSupport.park}</li>
2471 * </ul>
2472 *
2473 * <p>A thread in the waiting state is waiting for another thread to
2474 * perform a particular action.
2475 *
2476 * For example, a thread that has called {@code Object.wait()}
2477 * on an object is waiting for another thread to call
2478 * {@code Object.notify()} or {@code Object.notifyAll()} on
2479 * that object. A thread that has called {@code Thread.join()}
2480 * is waiting for a specified thread to terminate.
2481 */
2482 WAITING,
2483
2484 /**
2485 * Thread state for a waiting thread with a specified waiting time.
2486 * A thread is in the timed waiting state due to calling one of
2487 * the following methods with a specified positive waiting time:
2488 * <ul>
2489 * <li>{@link #sleep Thread.sleep}</li>
2490 * <li>{@link Object#wait(long) Object.wait} with timeout</li>
2491 * <li>{@link #join(long) Thread.join} with timeout</li>
2492 * <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
2493 * <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
2494 * </ul>
2495 */
2496 TIMED_WAITING,
2497
2498 /**
2499 * Thread state for a terminated thread.
2500 * The thread has completed execution.
2501 */
2502 TERMINATED;
2503 }
2504
2505 /**
2506 * Returns the state of this thread.
2507 * This method is designed for use in monitoring of the system state,
2508 * not for synchronization control.
2509 *
2510 * @return this thread's state.
2511 * @since 1.5
2512 */
2513 public State getState() {
2514 return threadState();
2515 }
2516
2517 /**
2518 * Returns the state of this thread.
2519 * This method can be used instead of getState as getState is not final and
2520 * so can be overridden to run arbitrary code.
2521 */
2522 State threadState() {
2523 return jdk.internal.misc.VM.toThreadState(holder.threadStatus);
2524 }
2525
2526 /**
2527 * Returns true if the thread has terminated.
2528 */
2529 boolean isTerminated() {
2530 return threadState() == State.TERMINATED;
2531 }
2532
2533 /**
2534 * Interface for handlers invoked when a {@code Thread} abruptly
2535 * terminates due to an uncaught exception.
2536 * <p>When a thread is about to terminate due to an uncaught exception
2537 * the Java Virtual Machine will query the thread for its
2538 * {@code UncaughtExceptionHandler} using
2539 * {@link #getUncaughtExceptionHandler} and will invoke the handler's
2540 * {@code uncaughtException} method, passing the thread and the
2541 * exception as arguments.
2542 * If a thread has not had its {@code UncaughtExceptionHandler}
2543 * explicitly set, then its {@code ThreadGroup} object acts as its
2544 * {@code UncaughtExceptionHandler}. If the {@code ThreadGroup} object
2545 * has no
2546 * special requirements for dealing with the exception, it can forward
2547 * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler
2548 * default uncaught exception handler}.
2549 *
2550 * @see #setDefaultUncaughtExceptionHandler
2551 * @see #setUncaughtExceptionHandler
2552 * @see ThreadGroup#uncaughtException
2553 * @since 1.5
2554 */
2555 @FunctionalInterface
2556 public interface UncaughtExceptionHandler {
2557 /**
2558 * Method invoked when the given thread terminates due to the
2559 * given uncaught exception.
2560 * <p>Any exception thrown by this method will be ignored by the
2561 * Java Virtual Machine.
2562 * @param t the thread
2563 * @param e the exception
2564 */
2565 void uncaughtException(Thread t, Throwable e);
2566 }
2567
2568 // null unless explicitly set
2569 private volatile UncaughtExceptionHandler uncaughtExceptionHandler;
2570
2571 // null unless explicitly set
2572 private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler;
2573
2574 /**
2575 * Set the default handler invoked when a thread abruptly terminates
2576 * due to an uncaught exception, and no other handler has been defined
2577 * for that thread.
2578 *
2579 * <p>Uncaught exception handling is controlled first by the thread, then
2580 * by the thread's {@link ThreadGroup} object and finally by the default
2581 * uncaught exception handler. If the thread does not have an explicit
2582 * uncaught exception handler set, and the thread's thread group
2583 * (including parent thread groups) does not specialize its
2584 * {@code uncaughtException} method, then the default handler's
2585 * {@code uncaughtException} method will be invoked.
2586 * <p>By setting the default uncaught exception handler, an application
2587 * can change the way in which uncaught exceptions are handled (such as
2588 * logging to a specific device, or file) for those threads that would
2589 * already accept whatever "default" behavior the system
2590 * provided.
2591 *
2592 * <p>Note that the default uncaught exception handler should not usually
2593 * defer to the thread's {@code ThreadGroup} object, as that could cause
2594 * infinite recursion.
2595 *
2596 * @param ueh the object to use as the default uncaught exception handler.
2597 * If {@code null} then there is no default handler.
2598 *
2599 * @see #setUncaughtExceptionHandler
2600 * @see #getUncaughtExceptionHandler
2601 * @see ThreadGroup#uncaughtException
2602 * @since 1.5
2603 */
2604 public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler ueh) {
2605 defaultUncaughtExceptionHandler = ueh;
2606 }
2607
2608 /**
2609 * Returns the default handler invoked when a thread abruptly terminates
2610 * due to an uncaught exception. If the returned value is {@code null},
2611 * there is no default.
2612 * @since 1.5
2613 * @see #setDefaultUncaughtExceptionHandler
2614 * @return the default uncaught exception handler for all threads
2615 */
2616 public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler(){
2617 return defaultUncaughtExceptionHandler;
2618 }
2619
2620 /**
2621 * Returns the handler invoked when this thread abruptly terminates
2622 * due to an uncaught exception. If this thread has not had an
2623 * uncaught exception handler explicitly set then this thread's
2624 * {@code ThreadGroup} object is returned, unless this thread
2625 * has terminated, in which case {@code null} is returned.
2626 * @since 1.5
2627 * @return the uncaught exception handler for this thread
2628 */
2629 public UncaughtExceptionHandler getUncaughtExceptionHandler() {
2630 if (isTerminated()) {
2631 // uncaughtExceptionHandler may be set to null after thread terminates
2632 return null;
2633 } else {
2634 UncaughtExceptionHandler ueh = uncaughtExceptionHandler;
2635 return (ueh != null) ? ueh : getThreadGroup();
2636 }
2637 }
2638
2639 /**
2640 * Set the handler invoked when this thread abruptly terminates
2641 * due to an uncaught exception.
2642 * <p>A thread can take full control of how it responds to uncaught
2643 * exceptions by having its uncaught exception handler explicitly set.
2644 * If no such handler is set then the thread's {@code ThreadGroup}
2645 * object acts as its handler.
2646 * @param ueh the object to use as this thread's uncaught exception
2647 * handler. If {@code null} then this thread has no explicit handler.
2648 * @see #setDefaultUncaughtExceptionHandler
2649 * @see ThreadGroup#uncaughtException
2650 * @since 1.5
2651 */
2652 public void setUncaughtExceptionHandler(UncaughtExceptionHandler ueh) {
2653 uncaughtExceptionHandler(ueh);
2654 }
2655
2656 void uncaughtExceptionHandler(UncaughtExceptionHandler ueh) {
2657 uncaughtExceptionHandler = ueh;
2658 }
2659
2660 /**
2661 * Dispatch an uncaught exception to the handler. This method is
2662 * called when a thread terminates with an exception.
2663 */
2664 void dispatchUncaughtException(Throwable e) {
2665 getUncaughtExceptionHandler().uncaughtException(this, e);
2666 }
2667
2668 /**
2669 * Holder class for constants.
2670 */
2671 private static class Constants {
2672 // Thread group for virtual threads.
2673 static final ThreadGroup VTHREAD_GROUP;
2674
2675 static {
2676 ThreadGroup root = Thread.currentCarrierThread().getThreadGroup();
2677 for (ThreadGroup p; (p = root.getParent()) != null; ) {
2678 root = p;
2679 }
2680 VTHREAD_GROUP = new ThreadGroup(root, "VirtualThreads", MAX_PRIORITY, false);
2681 }
2682 }
2683
2684 /**
2685 * Returns the special ThreadGroup for virtual threads.
2686 */
2687 static ThreadGroup virtualThreadGroup() {
2688 return Constants.VTHREAD_GROUP;
2689 }
2690
2691 // The following three initially uninitialized fields are exclusively
2692 // managed by class java.util.concurrent.ThreadLocalRandom. These
2693 // fields are used to build the high-performance PRNGs in the
2694 // concurrent code.
2695
2696 /** The current seed for a ThreadLocalRandom */
2697 long threadLocalRandomSeed;
2698
2699 /** Probe hash value; nonzero if threadLocalRandomSeed initialized */
2700 int threadLocalRandomProbe;
2701
2702 /** Secondary seed isolated from public ThreadLocalRandom sequence */
2703 int threadLocalRandomSecondarySeed;
2704
2705 /** The thread container that this thread is in */
2706 private @Stable ThreadContainer container;
2707 ThreadContainer threadContainer() {
2708 return container;
2709 }
2710 void setThreadContainer(ThreadContainer container) {
2711 // assert this.container == null;
2712 this.container = container;
2713 }
2714
2715 /** The top of this stack of stackable scopes owned by this thread */
2716 private volatile StackableScope headStackableScopes;
2717 StackableScope headStackableScopes() {
2718 return headStackableScopes;
2719 }
2720 static void setHeadStackableScope(StackableScope scope) {
2721 currentThread().headStackableScopes = scope;
2722 }
2723
2724 /* Some private helper methods */
2725 private native void setPriority0(int newPriority);
2726 private native void interrupt0();
2727 private static native void clearInterruptEvent();
2728 private native void setNativeName(String name);
2729
2730 // The address of the next thread identifier, see ThreadIdentifiers.
2731 private static native long getNextThreadIdOffset();
2732 }