1 /* 2 * Copyright (c) 1994, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.lang; 27 28 import java.lang.ref.Reference; 29 import java.lang.ref.ReferenceQueue; 30 import java.lang.ref.WeakReference; 31 import java.security.AccessController; 32 import java.security.AccessControlContext; 33 import java.security.PrivilegedAction; 34 import java.util.Map; 35 import java.util.HashMap; 36 import java.util.concurrent.ConcurrentHashMap; 37 import java.util.concurrent.ConcurrentMap; 38 import java.util.concurrent.locks.LockSupport; 39 40 import jdk.internal.misc.TerminatingThreadLocal; 41 import sun.nio.ch.Interruptible; 42 import jdk.internal.reflect.CallerSensitive; 43 import jdk.internal.reflect.Reflection; 44 import sun.security.util.SecurityConstants; 45 import jdk.internal.HotSpotIntrinsicCandidate; 46 47 /** 48 * A <i>thread</i> is a thread of execution in a program. The Java 49 * Virtual Machine allows an application to have multiple threads of 50 * execution running concurrently. 51 * <p> 52 * Every thread has a priority. Threads with higher priority are 53 * executed in preference to threads with lower priority. Each thread 54 * may or may not also be marked as a daemon. When code running in 55 * some thread creates a new {@code Thread} object, the new 56 * thread has its priority initially set equal to the priority of the 57 * creating thread, and is a daemon thread if and only if the 58 * creating thread is a daemon. 59 * <p> 60 * When a Java Virtual Machine starts up, there is usually a single 61 * non-daemon thread (which typically calls the method named 62 * {@code main} of some designated class). The Java Virtual 63 * Machine continues to execute threads until either of the following 64 * occurs: 65 * <ul> 66 * <li>The {@code exit} method of class {@code Runtime} has been 67 * called and the security manager has permitted the exit operation 68 * to take place. 69 * <li>All threads that are not daemon threads have died, either by 70 * returning from the call to the {@code run} method or by 71 * throwing an exception that propagates beyond the {@code run} 72 * method. 73 * </ul> 74 * <p> 75 * There are two ways to create a new thread of execution. One is to 76 * declare a class to be a subclass of {@code Thread}. This 77 * subclass should override the {@code run} method of class 78 * {@code Thread}. An instance of the subclass can then be 79 * allocated and started. For example, a thread that computes primes 80 * larger than a stated value could be written as follows: 81 * <hr><blockquote><pre> 82 * class PrimeThread extends Thread { 83 * long minPrime; 84 * PrimeThread(long minPrime) { 85 * this.minPrime = minPrime; 86 * } 87 * 88 * public void run() { 89 * // compute primes larger than minPrime 90 * . . . 91 * } 92 * } 93 * </pre></blockquote><hr> 94 * <p> 95 * The following code would then create a thread and start it running: 96 * <blockquote><pre> 97 * PrimeThread p = new PrimeThread(143); 98 * p.start(); 99 * </pre></blockquote> 100 * <p> 101 * The other way to create a thread is to declare a class that 102 * implements the {@code Runnable} interface. That class then 103 * implements the {@code run} method. An instance of the class can 104 * then be allocated, passed as an argument when creating 105 * {@code Thread}, and started. The same example in this other 106 * style looks like the following: 107 * <hr><blockquote><pre> 108 * class PrimeRun implements Runnable { 109 * long minPrime; 110 * PrimeRun(long minPrime) { 111 * this.minPrime = minPrime; 112 * } 113 * 114 * public void run() { 115 * // compute primes larger than minPrime 116 * . . . 117 * } 118 * } 119 * </pre></blockquote><hr> 120 * <p> 121 * The following code would then create a thread and start it running: 122 * <blockquote><pre> 123 * PrimeRun p = new PrimeRun(143); 124 * new Thread(p).start(); 125 * </pre></blockquote> 126 * <p> 127 * Every thread has a name for identification purposes. More than 128 * one thread may have the same name. If a name is not specified when 129 * a thread is created, a new name is generated for it. 130 * <p> 131 * Unless otherwise noted, passing a {@code null} argument to a constructor 132 * or method in this class will cause a {@link NullPointerException} to be 133 * thrown. 134 * 135 * @author unascribed 136 * @see Runnable 137 * @see Runtime#exit(int) 138 * @see #run() 139 * @see #stop() 140 * @since 1.0 141 */ 142 public 143 class Thread implements Runnable { 144 /* Make sure registerNatives is the first thing <clinit> does. */ 145 private static native void registerNatives(); 146 static { 147 registerNatives(); 148 } 149 150 private volatile String name; 151 private int priority; 152 153 /* Whether or not the thread is a daemon thread. */ 154 private boolean daemon = false; 155 156 /* Fields reserved for exclusive use by the JVM */ 157 private boolean stillborn = false; 158 private long eetop; 159 160 /* What will be run. */ 161 private Runnable target; 162 163 /* The group of this thread */ 164 private ThreadGroup group; 165 166 /* The context ClassLoader for this thread */ 167 private ClassLoader contextClassLoader; 168 169 /* The inherited AccessControlContext of this thread */ 170 private AccessControlContext inheritedAccessControlContext; 171 172 /* For autonumbering anonymous threads. */ 173 private static int threadInitNumber; 174 private static synchronized int nextThreadNum() { 175 return threadInitNumber++; 176 } 177 178 /* ThreadLocal values pertaining to this thread. This map is maintained 179 * by the ThreadLocal class. */ 180 ThreadLocal.ThreadLocalMap threadLocals = null; 181 182 /* 183 * InheritableThreadLocal values pertaining to this thread. This map is 184 * maintained by the InheritableThreadLocal class. 185 */ 186 ThreadLocal.ThreadLocalMap inheritableThreadLocals = null; 187 188 /* 189 * The requested stack size for this thread, or 0 if the creator did 190 * not specify a stack size. It is up to the VM to do whatever it 191 * likes with this number; some VMs will ignore it. 192 */ 193 private final long stackSize; 194 195 /* 196 * JVM-private state that persists after native thread termination. 197 */ 198 private long nativeParkEventPointer; 199 200 /* 201 * Thread ID 202 */ 203 private final long tid; 204 205 /* For generating thread ID */ 206 private static long threadSeqNumber; 207 208 private static synchronized long nextThreadID() { 209 return ++threadSeqNumber; 210 } 211 212 /* 213 * Java thread status for tools, default indicates thread 'not yet started' 214 */ 215 private volatile int threadStatus; 216 217 /** 218 * The argument supplied to the current call to 219 * java.util.concurrent.locks.LockSupport.park. 220 * Set by (private) java.util.concurrent.locks.LockSupport.setBlocker 221 * Accessed using java.util.concurrent.locks.LockSupport.getBlocker 222 */ 223 volatile Object parkBlocker; 224 225 /* The object in which this thread is blocked in an interruptible I/O 226 * operation, if any. The blocker's interrupt method should be invoked 227 * after setting this thread's interrupt status. 228 */ 229 private volatile Interruptible blocker; 230 private final Object blockerLock = new Object(); 231 232 /* Set the blocker field; invoked via jdk.internal.misc.SharedSecrets 233 * from java.nio code 234 */ 235 static void blockedOn(Interruptible b) { 236 Thread me = Thread.currentThread(); 237 synchronized (me.blockerLock) { 238 me.blocker = b; 239 } 240 } 241 242 /** 243 * The minimum priority that a thread can have. 244 */ 245 public static final int MIN_PRIORITY = 1; 246 247 /** 248 * The default priority that is assigned to a thread. 249 */ 250 public static final int NORM_PRIORITY = 5; 251 252 /** 253 * The maximum priority that a thread can have. 254 */ 255 public static final int MAX_PRIORITY = 10; 256 257 /** 258 * Returns a reference to the currently executing thread object. 259 * 260 * @return the currently executing thread. 261 */ 262 @HotSpotIntrinsicCandidate 263 public static native Thread currentThread(); 264 265 /** 266 * A hint to the scheduler that the current thread is willing to yield 267 * its current use of a processor. The scheduler is free to ignore this 268 * hint. 269 * 270 * <p> Yield is a heuristic attempt to improve relative progression 271 * between threads that would otherwise over-utilise a CPU. Its use 272 * should be combined with detailed profiling and benchmarking to 273 * ensure that it actually has the desired effect. 274 * 275 * <p> It is rarely appropriate to use this method. It may be useful 276 * for debugging or testing purposes, where it may help to reproduce 277 * bugs due to race conditions. It may also be useful when designing 278 * concurrency control constructs such as the ones in the 279 * {@link java.util.concurrent.locks} package. 280 */ 281 public static native void yield(); 282 283 /** 284 * Causes the currently executing thread to sleep (temporarily cease 285 * execution) for the specified number of milliseconds, subject to 286 * the precision and accuracy of system timers and schedulers. The thread 287 * does not lose ownership of any monitors. 288 * 289 * @param millis 290 * the length of time to sleep in milliseconds 291 * 292 * @throws IllegalArgumentException 293 * if the value of {@code millis} is negative 294 * 295 * @throws InterruptedException 296 * if any thread has interrupted the current thread. The 297 * <i>interrupted status</i> of the current thread is 298 * cleared when this exception is thrown. 299 */ 300 public static native void sleep(long millis) throws InterruptedException; 301 302 /** 303 * Causes the currently executing thread to sleep (temporarily cease 304 * execution) for the specified number of milliseconds plus the specified 305 * number of nanoseconds, subject to the precision and accuracy of system 306 * timers and schedulers. The thread does not lose ownership of any 307 * monitors. 308 * 309 * @param millis 310 * the length of time to sleep in milliseconds 311 * 312 * @param nanos 313 * {@code 0-999999} additional nanoseconds to sleep 314 * 315 * @throws IllegalArgumentException 316 * if the value of {@code millis} is negative, or the value of 317 * {@code nanos} is not in the range {@code 0-999999} 318 * 319 * @throws InterruptedException 320 * if any thread has interrupted the current thread. The 321 * <i>interrupted status</i> of the current thread is 322 * cleared when this exception is thrown. 323 */ 324 public static void sleep(long millis, int nanos) 325 throws InterruptedException { 326 if (millis < 0) { 327 throw new IllegalArgumentException("timeout value is negative"); 328 } 329 330 if (nanos < 0 || nanos > 999999) { 331 throw new IllegalArgumentException( 332 "nanosecond timeout value out of range"); 333 } 334 335 if (nanos >= 500000 || (nanos != 0 && millis == 0)) { 336 millis++; 337 } 338 339 sleep(millis); 340 } 341 342 /** 343 * Indicates that the caller is momentarily unable to progress, until the 344 * occurrence of one or more actions on the part of other activities. By 345 * invoking this method within each iteration of a spin-wait loop construct, 346 * the calling thread indicates to the runtime that it is busy-waiting. 347 * The runtime may take action to improve the performance of invoking 348 * spin-wait loop constructions. 349 * 350 * @apiNote 351 * As an example consider a method in a class that spins in a loop until 352 * some flag is set outside of that method. A call to the {@code onSpinWait} 353 * method should be placed inside the spin loop. 354 * <pre>{@code 355 * class EventHandler { 356 * volatile boolean eventNotificationNotReceived; 357 * void waitForEventAndHandleIt() { 358 * while ( eventNotificationNotReceived ) { 359 * java.lang.Thread.onSpinWait(); 360 * } 361 * readAndProcessEvent(); 362 * } 363 * 364 * void readAndProcessEvent() { 365 * // Read event from some source and process it 366 * . . . 367 * } 368 * } 369 * }</pre> 370 * <p> 371 * The code above would remain correct even if the {@code onSpinWait} 372 * method was not called at all. However on some architectures the Java 373 * Virtual Machine may issue the processor instructions to address such 374 * code patterns in a more beneficial way. 375 * 376 * @since 9 377 */ 378 @HotSpotIntrinsicCandidate 379 public static void onSpinWait() {} 380 381 /** 382 * Initializes a Thread. 383 * 384 * @param g the Thread group 385 * @param target the object whose run() method gets called 386 * @param name the name of the new Thread 387 * @param stackSize the desired stack size for the new thread, or 388 * zero to indicate that this parameter is to be ignored. 389 * @param acc the AccessControlContext to inherit, or 390 * AccessController.getContext() if null 391 * @param inheritThreadLocals if {@code true}, inherit initial values for 392 * inheritable thread-locals from the constructing thread 393 */ 394 private Thread(ThreadGroup g, Runnable target, String name, 395 long stackSize, AccessControlContext acc, 396 boolean inheritThreadLocals) { 397 if (name == null) { 398 throw new NullPointerException("name cannot be null"); 399 } 400 401 this.name = name; 402 403 Thread parent = currentThread(); 404 SecurityManager security = System.getSecurityManager(); 405 if (g == null) { 406 /* Determine if it's an applet or not */ 407 408 /* If there is a security manager, ask the security manager 409 what to do. */ 410 if (security != null) { 411 g = security.getThreadGroup(); 412 } 413 414 /* If the security manager doesn't have a strong opinion 415 on the matter, use the parent thread group. */ 416 if (g == null) { 417 g = parent.getThreadGroup(); 418 } 419 } 420 421 /* checkAccess regardless of whether or not threadgroup is 422 explicitly passed in. */ 423 g.checkAccess(); 424 425 /* 426 * Do we have the required permissions? 427 */ 428 if (security != null) { 429 if (isCCLOverridden(getClass())) { 430 security.checkPermission( 431 SecurityConstants.SUBCLASS_IMPLEMENTATION_PERMISSION); 432 } 433 } 434 435 g.addUnstarted(); 436 437 this.group = g; 438 this.daemon = parent.isDaemon(); 439 this.priority = parent.getPriority(); 440 if (security == null || isCCLOverridden(parent.getClass())) 441 this.contextClassLoader = parent.getContextClassLoader(); 442 else 443 this.contextClassLoader = parent.contextClassLoader; 444 this.inheritedAccessControlContext = 445 acc != null ? acc : AccessController.getContext(); 446 this.target = target; 447 setPriority(priority); 448 if (inheritThreadLocals && parent.inheritableThreadLocals != null) 449 this.inheritableThreadLocals = 450 ThreadLocal.createInheritedMap(parent.inheritableThreadLocals); 451 /* Stash the specified stack size in case the VM cares */ 452 this.stackSize = stackSize; 453 454 /* Set thread ID */ 455 this.tid = nextThreadID(); 456 } 457 458 /** 459 * Throws CloneNotSupportedException as a Thread can not be meaningfully 460 * cloned. Construct a new Thread instead. 461 * 462 * @throws CloneNotSupportedException 463 * always 464 */ 465 @Override 466 protected Object clone() throws CloneNotSupportedException { 467 throw new CloneNotSupportedException(); 468 } 469 470 /** 471 * Allocates a new {@code Thread} object. This constructor has the same 472 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 473 * {@code (null, null, gname)}, where {@code gname} is a newly generated 474 * name. Automatically generated names are of the form 475 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer. 476 */ 477 public Thread() { 478 this(null, null, "Thread-" + nextThreadNum(), 0); 479 } 480 481 /** 482 * Allocates a new {@code Thread} object. This constructor has the same 483 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 484 * {@code (null, target, gname)}, where {@code gname} is a newly generated 485 * name. Automatically generated names are of the form 486 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer. 487 * 488 * @param target 489 * the object whose {@code run} method is invoked when this thread 490 * is started. If {@code null}, this classes {@code run} method does 491 * nothing. 492 */ 493 public Thread(Runnable target) { 494 this(null, target, "Thread-" + nextThreadNum(), 0); 495 } 496 497 /** 498 * Creates a new Thread that inherits the given AccessControlContext 499 * but thread-local variables are not inherited. 500 * This is not a public constructor. 501 */ 502 Thread(Runnable target, AccessControlContext acc) { 503 this(null, target, "Thread-" + nextThreadNum(), 0, acc, false); 504 } 505 506 /** 507 * Allocates a new {@code Thread} object. This constructor has the same 508 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 509 * {@code (group, target, gname)} ,where {@code gname} is a newly generated 510 * name. Automatically generated names are of the form 511 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer. 512 * 513 * @param group 514 * the thread group. If {@code null} and there is a security 515 * manager, the group is determined by {@linkplain 516 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. 517 * If there is not a security manager or {@code 518 * SecurityManager.getThreadGroup()} returns {@code null}, the group 519 * is set to the current thread's thread group. 520 * 521 * @param target 522 * the object whose {@code run} method is invoked when this thread 523 * is started. If {@code null}, this thread's run method is invoked. 524 * 525 * @throws SecurityException 526 * if the current thread cannot create a thread in the specified 527 * thread group 528 */ 529 public Thread(ThreadGroup group, Runnable target) { 530 this(group, target, "Thread-" + nextThreadNum(), 0); 531 } 532 533 /** 534 * Allocates a new {@code Thread} object. This constructor has the same 535 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 536 * {@code (null, null, name)}. 537 * 538 * @param name 539 * the name of the new thread 540 */ 541 public Thread(String name) { 542 this(null, null, name, 0); 543 } 544 545 /** 546 * Allocates a new {@code Thread} object. This constructor has the same 547 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 548 * {@code (group, null, name)}. 549 * 550 * @param group 551 * the thread group. If {@code null} and there is a security 552 * manager, the group is determined by {@linkplain 553 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. 554 * If there is not a security manager or {@code 555 * SecurityManager.getThreadGroup()} returns {@code null}, the group 556 * is set to the current thread's thread group. 557 * 558 * @param name 559 * the name of the new thread 560 * 561 * @throws SecurityException 562 * if the current thread cannot create a thread in the specified 563 * thread group 564 */ 565 public Thread(ThreadGroup group, String name) { 566 this(group, null, name, 0); 567 } 568 569 /** 570 * Allocates a new {@code Thread} object. This constructor has the same 571 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 572 * {@code (null, target, name)}. 573 * 574 * @param target 575 * the object whose {@code run} method is invoked when this thread 576 * is started. If {@code null}, this thread's run method is invoked. 577 * 578 * @param name 579 * the name of the new thread 580 */ 581 public Thread(Runnable target, String name) { 582 this(null, target, name, 0); 583 } 584 585 /** 586 * Allocates a new {@code Thread} object so that it has {@code target} 587 * as its run object, has the specified {@code name} as its name, 588 * and belongs to the thread group referred to by {@code group}. 589 * 590 * <p>If there is a security manager, its 591 * {@link SecurityManager#checkAccess(ThreadGroup) checkAccess} 592 * method is invoked with the ThreadGroup as its argument. 593 * 594 * <p>In addition, its {@code checkPermission} method is invoked with 595 * the {@code RuntimePermission("enableContextClassLoaderOverride")} 596 * permission when invoked directly or indirectly by the constructor 597 * of a subclass which overrides the {@code getContextClassLoader} 598 * or {@code setContextClassLoader} methods. 599 * 600 * <p>The priority of the newly created thread is set equal to the 601 * priority of the thread creating it, that is, the currently running 602 * thread. The method {@linkplain #setPriority setPriority} may be 603 * used to change the priority to a new value. 604 * 605 * <p>The newly created thread is initially marked as being a daemon 606 * thread if and only if the thread creating it is currently marked 607 * as a daemon thread. The method {@linkplain #setDaemon setDaemon} 608 * may be used to change whether or not a thread is a daemon. 609 * 610 * @param group 611 * the thread group. If {@code null} and there is a security 612 * manager, the group is determined by {@linkplain 613 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. 614 * If there is not a security manager or {@code 615 * SecurityManager.getThreadGroup()} returns {@code null}, the group 616 * is set to the current thread's thread group. 617 * 618 * @param target 619 * the object whose {@code run} method is invoked when this thread 620 * is started. If {@code null}, this thread's run method is invoked. 621 * 622 * @param name 623 * the name of the new thread 624 * 625 * @throws SecurityException 626 * if the current thread cannot create a thread in the specified 627 * thread group or cannot override the context class loader methods. 628 */ 629 public Thread(ThreadGroup group, Runnable target, String name) { 630 this(group, target, name, 0); 631 } 632 633 /** 634 * Allocates a new {@code Thread} object so that it has {@code target} 635 * as its run object, has the specified {@code name} as its name, 636 * and belongs to the thread group referred to by {@code group}, and has 637 * the specified <i>stack size</i>. 638 * 639 * <p>This constructor is identical to {@link 640 * #Thread(ThreadGroup,Runnable,String)} with the exception of the fact 641 * that it allows the thread stack size to be specified. The stack size 642 * is the approximate number of bytes of address space that the virtual 643 * machine is to allocate for this thread's stack. <b>The effect of the 644 * {@code stackSize} parameter, if any, is highly platform dependent.</b> 645 * 646 * <p>On some platforms, specifying a higher value for the 647 * {@code stackSize} parameter may allow a thread to achieve greater 648 * recursion depth before throwing a {@link StackOverflowError}. 649 * Similarly, specifying a lower value may allow a greater number of 650 * threads to exist concurrently without throwing an {@link 651 * OutOfMemoryError} (or other internal error). The details of 652 * the relationship between the value of the {@code stackSize} parameter 653 * and the maximum recursion depth and concurrency level are 654 * platform-dependent. <b>On some platforms, the value of the 655 * {@code stackSize} parameter may have no effect whatsoever.</b> 656 * 657 * <p>The virtual machine is free to treat the {@code stackSize} 658 * parameter as a suggestion. If the specified value is unreasonably low 659 * for the platform, the virtual machine may instead use some 660 * platform-specific minimum value; if the specified value is unreasonably 661 * high, the virtual machine may instead use some platform-specific 662 * maximum. Likewise, the virtual machine is free to round the specified 663 * value up or down as it sees fit (or to ignore it completely). 664 * 665 * <p>Specifying a value of zero for the {@code stackSize} parameter will 666 * cause this constructor to behave exactly like the 667 * {@code Thread(ThreadGroup, Runnable, String)} constructor. 668 * 669 * <p><i>Due to the platform-dependent nature of the behavior of this 670 * constructor, extreme care should be exercised in its use. 671 * The thread stack size necessary to perform a given computation will 672 * likely vary from one JRE implementation to another. In light of this 673 * variation, careful tuning of the stack size parameter may be required, 674 * and the tuning may need to be repeated for each JRE implementation on 675 * which an application is to run.</i> 676 * 677 * <p>Implementation note: Java platform implementers are encouraged to 678 * document their implementation's behavior with respect to the 679 * {@code stackSize} parameter. 680 * 681 * 682 * @param group 683 * the thread group. If {@code null} and there is a security 684 * manager, the group is determined by {@linkplain 685 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. 686 * If there is not a security manager or {@code 687 * SecurityManager.getThreadGroup()} returns {@code null}, the group 688 * is set to the current thread's thread group. 689 * 690 * @param target 691 * the object whose {@code run} method is invoked when this thread 692 * is started. If {@code null}, this thread's run method is invoked. 693 * 694 * @param name 695 * the name of the new thread 696 * 697 * @param stackSize 698 * the desired stack size for the new thread, or zero to indicate 699 * that this parameter is to be ignored. 700 * 701 * @throws SecurityException 702 * if the current thread cannot create a thread in the specified 703 * thread group 704 * 705 * @since 1.4 706 */ 707 public Thread(ThreadGroup group, Runnable target, String name, 708 long stackSize) { 709 this(group, target, name, stackSize, null, true); 710 } 711 712 /** 713 * Allocates a new {@code Thread} object so that it has {@code target} 714 * as its run object, has the specified {@code name} as its name, 715 * belongs to the thread group referred to by {@code group}, has 716 * the specified {@code stackSize}, and inherits initial values for 717 * {@linkplain InheritableThreadLocal inheritable thread-local} variables 718 * if {@code inheritThreadLocals} is {@code true}. 719 * 720 * <p> This constructor is identical to {@link 721 * #Thread(ThreadGroup,Runnable,String,long)} with the added ability to 722 * suppress, or not, the inheriting of initial values for inheritable 723 * thread-local variables from the constructing thread. This allows for 724 * finer grain control over inheritable thread-locals. Care must be taken 725 * when passing a value of {@code false} for {@code inheritThreadLocals}, 726 * as it may lead to unexpected behavior if the new thread executes code 727 * that expects a specific thread-local value to be inherited. 728 * 729 * <p> Specifying a value of {@code true} for the {@code inheritThreadLocals} 730 * parameter will cause this constructor to behave exactly like the 731 * {@code Thread(ThreadGroup, Runnable, String, long)} constructor. 732 * 733 * @param group 734 * the thread group. If {@code null} and there is a security 735 * manager, the group is determined by {@linkplain 736 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. 737 * If there is not a security manager or {@code 738 * SecurityManager.getThreadGroup()} returns {@code null}, the group 739 * is set to the current thread's thread group. 740 * 741 * @param target 742 * the object whose {@code run} method is invoked when this thread 743 * is started. If {@code null}, this thread's run method is invoked. 744 * 745 * @param name 746 * the name of the new thread 747 * 748 * @param stackSize 749 * the desired stack size for the new thread, or zero to indicate 750 * that this parameter is to be ignored 751 * 752 * @param inheritThreadLocals 753 * if {@code true}, inherit initial values for inheritable 754 * thread-locals from the constructing thread, otherwise no initial 755 * values are inherited 756 * 757 * @throws SecurityException 758 * if the current thread cannot create a thread in the specified 759 * thread group 760 * 761 * @since 9 762 */ 763 public Thread(ThreadGroup group, Runnable target, String name, 764 long stackSize, boolean inheritThreadLocals) { 765 this(group, target, name, stackSize, null, inheritThreadLocals); 766 } 767 768 /** 769 * Causes this thread to begin execution; the Java Virtual Machine 770 * calls the {@code run} method of this thread. 771 * <p> 772 * The result is that two threads are running concurrently: the 773 * current thread (which returns from the call to the 774 * {@code start} method) and the other thread (which executes its 775 * {@code run} method). 776 * <p> 777 * It is never legal to start a thread more than once. 778 * In particular, a thread may not be restarted once it has completed 779 * execution. 780 * 781 * @throws IllegalThreadStateException if the thread was already started. 782 * @see #run() 783 * @see #stop() 784 */ 785 public synchronized void start() { 786 /** 787 * This method is not invoked for the main method thread or "system" 788 * group threads created/set up by the VM. Any new functionality added 789 * to this method in the future may have to also be added to the VM. 790 * 791 * A zero status value corresponds to state "NEW". 792 */ 793 if (threadStatus != 0) 794 throw new IllegalThreadStateException(); 795 796 /* Notify the group that this thread is about to be started 797 * so that it can be added to the group's list of threads 798 * and the group's unstarted count can be decremented. */ 799 group.add(this); 800 801 boolean started = false; 802 try { 803 start0(); 804 started = true; 805 } finally { 806 try { 807 if (!started) { 808 group.threadStartFailed(this); 809 } 810 } catch (Throwable ignore) { 811 /* do nothing. If start0 threw a Throwable then 812 it will be passed up the call stack */ 813 } 814 } 815 } 816 817 private native void start0(); 818 819 /** 820 * If this thread was constructed using a separate 821 * {@code Runnable} run object, then that 822 * {@code Runnable} object's {@code run} method is called; 823 * otherwise, this method does nothing and returns. 824 * <p> 825 * Subclasses of {@code Thread} should override this method. 826 * 827 * @see #start() 828 * @see #stop() 829 * @see #Thread(ThreadGroup, Runnable, String) 830 */ 831 @Override 832 public void run() { 833 if (target != null) { 834 target.run(); 835 } 836 } 837 838 /** 839 * This method is called by the system to give a Thread 840 * a chance to clean up before it actually exits. 841 */ 842 private void exit() { 843 if (threadLocals != null && TerminatingThreadLocal.REGISTRY.isPresent()) { 844 TerminatingThreadLocal.threadTerminated(); 845 } 846 if (group != null) { 847 group.threadTerminated(this); 848 group = null; 849 } 850 /* Aggressively null out all reference fields: see bug 4006245 */ 851 target = null; 852 /* Speed the release of some of these resources */ 853 threadLocals = null; 854 inheritableThreadLocals = null; 855 inheritedAccessControlContext = null; 856 blocker = null; 857 uncaughtExceptionHandler = null; 858 } 859 860 /** 861 * Forces the thread to stop executing. 862 * <p> 863 * If there is a security manager installed, its {@code checkAccess} 864 * method is called with {@code this} 865 * as its argument. This may result in a 866 * {@code SecurityException} being raised (in the current thread). 867 * <p> 868 * If this thread is different from the current thread (that is, the current 869 * thread is trying to stop a thread other than itself), the 870 * security manager's {@code checkPermission} method (with a 871 * {@code RuntimePermission("stopThread")} argument) is called in 872 * addition. 873 * Again, this may result in throwing a 874 * {@code SecurityException} (in the current thread). 875 * <p> 876 * The thread represented by this thread is forced to stop whatever 877 * it is doing abnormally and to throw a newly created 878 * {@code ThreadDeath} object as an exception. 879 * <p> 880 * It is permitted to stop a thread that has not yet been started. 881 * If the thread is eventually started, it immediately terminates. 882 * <p> 883 * An application should not normally try to catch 884 * {@code ThreadDeath} unless it must do some extraordinary 885 * cleanup operation (note that the throwing of 886 * {@code ThreadDeath} causes {@code finally} clauses of 887 * {@code try} statements to be executed before the thread 888 * officially dies). If a {@code catch} clause catches a 889 * {@code ThreadDeath} object, it is important to rethrow the 890 * object so that the thread actually dies. 891 * <p> 892 * The top-level error handler that reacts to otherwise uncaught 893 * exceptions does not print out a message or otherwise notify the 894 * application if the uncaught exception is an instance of 895 * {@code ThreadDeath}. 896 * 897 * @throws SecurityException if the current thread cannot 898 * modify this thread. 899 * @see #interrupt() 900 * @see #checkAccess() 901 * @see #run() 902 * @see #start() 903 * @see ThreadDeath 904 * @see ThreadGroup#uncaughtException(Thread,Throwable) 905 * @see SecurityManager#checkAccess(Thread) 906 * @see SecurityManager#checkPermission 907 * @deprecated This method is inherently unsafe. Stopping a thread with 908 * Thread.stop causes it to unlock all of the monitors that it 909 * has locked (as a natural consequence of the unchecked 910 * {@code ThreadDeath} exception propagating up the stack). If 911 * any of the objects previously protected by these monitors were in 912 * an inconsistent state, the damaged objects become visible to 913 * other threads, potentially resulting in arbitrary behavior. Many 914 * uses of {@code stop} should be replaced by code that simply 915 * modifies some variable to indicate that the target thread should 916 * stop running. The target thread should check this variable 917 * regularly, and return from its run method in an orderly fashion 918 * if the variable indicates that it is to stop running. If the 919 * target thread waits for long periods (on a condition variable, 920 * for example), the {@code interrupt} method should be used to 921 * interrupt the wait. 922 * For more information, see 923 * <a href="{@docRoot}/java.base/java/lang/doc-files/threadPrimitiveDeprecation.html">Why 924 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. 925 */ 926 @Deprecated(since="1.2") 927 public final void stop() { 928 SecurityManager security = System.getSecurityManager(); 929 if (security != null) { 930 checkAccess(); 931 if (this != Thread.currentThread()) { 932 security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION); 933 } 934 } 935 // A zero status value corresponds to "NEW", it can't change to 936 // not-NEW because we hold the lock. 937 if (threadStatus != 0) { 938 resume(); // Wake up thread if it was suspended; no-op otherwise 939 } 940 941 // The VM can handle all thread states 942 stop0(new ThreadDeath()); 943 } 944 945 /** 946 * Interrupts this thread. 947 * 948 * <p> Unless the current thread is interrupting itself, which is 949 * always permitted, the {@link #checkAccess() checkAccess} method 950 * of this thread is invoked, which may cause a {@link 951 * SecurityException} to be thrown. 952 * 953 * <p> If this thread is blocked in an invocation of the {@link 954 * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link 955 * Object#wait(long, int) wait(long, int)} methods of the {@link Object} 956 * class, or of the {@link #join()}, {@link #join(long)}, {@link 957 * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)}, 958 * methods of this class, then its interrupt status will be cleared and it 959 * will receive an {@link InterruptedException}. 960 * 961 * <p> If this thread is blocked in an I/O operation upon an {@link 962 * java.nio.channels.InterruptibleChannel InterruptibleChannel} 963 * then the channel will be closed, the thread's interrupt 964 * status will be set, and the thread will receive a {@link 965 * java.nio.channels.ClosedByInterruptException}. 966 * 967 * <p> If this thread is blocked in a {@link java.nio.channels.Selector} 968 * then the thread's interrupt status will be set and it will return 969 * immediately from the selection operation, possibly with a non-zero 970 * value, just as if the selector's {@link 971 * java.nio.channels.Selector#wakeup wakeup} method were invoked. 972 * 973 * <p> If none of the previous conditions hold then this thread's interrupt 974 * status will be set. </p> 975 * 976 * <p> Interrupting a thread that is not alive need not have any effect. 977 * 978 * @throws SecurityException 979 * if the current thread cannot modify this thread 980 * 981 * @revised 6.0 982 * @spec JSR-51 983 */ 984 public void interrupt() { 985 if (this != Thread.currentThread()) { 986 checkAccess(); 987 988 // thread may be blocked in an I/O operation 989 synchronized (blockerLock) { 990 Interruptible b = blocker; 991 if (b != null) { 992 interrupt0(); // set interrupt status 993 b.interrupt(this); 994 return; 995 } 996 } 997 } 998 999 // set interrupt status 1000 interrupt0(); 1001 } 1002 1003 /** 1004 * Tests whether the current thread has been interrupted. The 1005 * <i>interrupted status</i> of the thread is cleared by this method. In 1006 * other words, if this method were to be called twice in succession, the 1007 * second call would return false (unless the current thread were 1008 * interrupted again, after the first call had cleared its interrupted 1009 * status and before the second call had examined it). 1010 * 1011 * <p>A thread interruption ignored because a thread was not alive 1012 * at the time of the interrupt will be reflected by this method 1013 * returning false. 1014 * 1015 * @return {@code true} if the current thread has been interrupted; 1016 * {@code false} otherwise. 1017 * @see #isInterrupted() 1018 * @revised 6.0 1019 */ 1020 public static boolean interrupted() { 1021 return currentThread().isInterrupted(true); 1022 } 1023 1024 /** 1025 * Tests whether this thread has been interrupted. The <i>interrupted 1026 * status</i> of the thread is unaffected by this method. 1027 * 1028 * <p>A thread interruption ignored because a thread was not alive 1029 * at the time of the interrupt will be reflected by this method 1030 * returning false. 1031 * 1032 * @return {@code true} if this thread has been interrupted; 1033 * {@code false} otherwise. 1034 * @see #interrupted() 1035 * @revised 6.0 1036 */ 1037 public boolean isInterrupted() { 1038 return isInterrupted(false); 1039 } 1040 1041 /** 1042 * Tests if some Thread has been interrupted. The interrupted state 1043 * is reset or not based on the value of ClearInterrupted that is 1044 * passed. 1045 */ 1046 @HotSpotIntrinsicCandidate 1047 private native boolean isInterrupted(boolean ClearInterrupted); 1048 1049 /** 1050 * Tests if this thread is alive. A thread is alive if it has 1051 * been started and has not yet died. 1052 * 1053 * @return {@code true} if this thread is alive; 1054 * {@code false} otherwise. 1055 */ 1056 public final native boolean isAlive(); 1057 1058 /** 1059 * Suspends this thread. 1060 * <p> 1061 * First, the {@code checkAccess} method of this thread is called 1062 * with no arguments. This may result in throwing a 1063 * {@code SecurityException }(in the current thread). 1064 * <p> 1065 * If the thread is alive, it is suspended and makes no further 1066 * progress unless and until it is resumed. 1067 * 1068 * @throws SecurityException if the current thread cannot modify 1069 * this thread. 1070 * @see #checkAccess 1071 * @deprecated This method has been deprecated, as it is 1072 * inherently deadlock-prone. If the target thread holds a lock on the 1073 * monitor protecting a critical system resource when it is suspended, no 1074 * thread can access this resource until the target thread is resumed. If 1075 * the thread that would resume the target thread attempts to lock this 1076 * monitor prior to calling {@code resume}, deadlock results. Such 1077 * deadlocks typically manifest themselves as "frozen" processes. 1078 * For more information, see 1079 * <a href="{@docRoot}/java.base/java/lang/doc-files/threadPrimitiveDeprecation.html">Why 1080 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. 1081 */ 1082 @Deprecated(since="1.2") 1083 public final void suspend() { 1084 checkAccess(); 1085 suspend0(); 1086 } 1087 1088 /** 1089 * Resumes a suspended thread. 1090 * <p> 1091 * First, the {@code checkAccess} method of this thread is called 1092 * with no arguments. This may result in throwing a 1093 * {@code SecurityException} (in the current thread). 1094 * <p> 1095 * If the thread is alive but suspended, it is resumed and is 1096 * permitted to make progress in its execution. 1097 * 1098 * @throws SecurityException if the current thread cannot modify this 1099 * thread. 1100 * @see #checkAccess 1101 * @see #suspend() 1102 * @deprecated This method exists solely for use with {@link #suspend}, 1103 * which has been deprecated because it is deadlock-prone. 1104 * For more information, see 1105 * <a href="{@docRoot}/java.base/java/lang/doc-files/threadPrimitiveDeprecation.html">Why 1106 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. 1107 */ 1108 @Deprecated(since="1.2") 1109 public final void resume() { 1110 checkAccess(); 1111 resume0(); 1112 } 1113 1114 /** 1115 * Changes the priority of this thread. 1116 * <p> 1117 * First the {@code checkAccess} method of this thread is called 1118 * with no arguments. This may result in throwing a {@code SecurityException}. 1119 * <p> 1120 * Otherwise, the priority of this thread is set to the smaller of 1121 * the specified {@code newPriority} and the maximum permitted 1122 * priority of the thread's thread group. 1123 * 1124 * @param newPriority priority to set this thread to 1125 * @throws IllegalArgumentException If the priority is not in the 1126 * range {@code MIN_PRIORITY} to 1127 * {@code MAX_PRIORITY}. 1128 * @throws SecurityException if the current thread cannot modify 1129 * this thread. 1130 * @see #getPriority 1131 * @see #checkAccess() 1132 * @see #getThreadGroup() 1133 * @see #MAX_PRIORITY 1134 * @see #MIN_PRIORITY 1135 * @see ThreadGroup#getMaxPriority() 1136 */ 1137 public final void setPriority(int newPriority) { 1138 ThreadGroup g; 1139 checkAccess(); 1140 if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) { 1141 throw new IllegalArgumentException(); 1142 } 1143 if((g = getThreadGroup()) != null) { 1144 if (newPriority > g.getMaxPriority()) { 1145 newPriority = g.getMaxPriority(); 1146 } 1147 setPriority0(priority = newPriority); 1148 } 1149 } 1150 1151 /** 1152 * Returns this thread's priority. 1153 * 1154 * @return this thread's priority. 1155 * @see #setPriority 1156 */ 1157 public final int getPriority() { 1158 return priority; 1159 } 1160 1161 /** 1162 * Changes the name of this thread to be equal to the argument {@code name}. 1163 * <p> 1164 * First the {@code checkAccess} method of this thread is called 1165 * with no arguments. This may result in throwing a 1166 * {@code SecurityException}. 1167 * 1168 * @param name the new name for this thread. 1169 * @throws SecurityException if the current thread cannot modify this 1170 * thread. 1171 * @see #getName 1172 * @see #checkAccess() 1173 */ 1174 public final synchronized void setName(String name) { 1175 checkAccess(); 1176 if (name == null) { 1177 throw new NullPointerException("name cannot be null"); 1178 } 1179 1180 this.name = name; 1181 if (threadStatus != 0) { 1182 setNativeName(name); 1183 } 1184 } 1185 1186 /** 1187 * Returns this thread's name. 1188 * 1189 * @return this thread's name. 1190 * @see #setName(String) 1191 */ 1192 public final String getName() { 1193 return name; 1194 } 1195 1196 /** 1197 * Returns the thread group to which this thread belongs. 1198 * This method returns null if this thread has died 1199 * (been stopped). 1200 * 1201 * @return this thread's thread group. 1202 */ 1203 public final ThreadGroup getThreadGroup() { 1204 return group; 1205 } 1206 1207 /** 1208 * Returns an estimate of the number of active threads in the current 1209 * thread's {@linkplain java.lang.ThreadGroup thread group} and its 1210 * subgroups. Recursively iterates over all subgroups in the current 1211 * thread's thread group. 1212 * 1213 * <p> The value returned is only an estimate because the number of 1214 * threads may change dynamically while this method traverses internal 1215 * data structures, and might be affected by the presence of certain 1216 * system threads. This method is intended primarily for debugging 1217 * and monitoring purposes. 1218 * 1219 * @return an estimate of the number of active threads in the current 1220 * thread's thread group and in any other thread group that 1221 * has the current thread's thread group as an ancestor 1222 */ 1223 public static int activeCount() { 1224 return currentThread().getThreadGroup().activeCount(); 1225 } 1226 1227 /** 1228 * Copies into the specified array every active thread in the current 1229 * thread's thread group and its subgroups. This method simply 1230 * invokes the {@link java.lang.ThreadGroup#enumerate(Thread[])} 1231 * method of the current thread's thread group. 1232 * 1233 * <p> An application might use the {@linkplain #activeCount activeCount} 1234 * method to get an estimate of how big the array should be, however 1235 * <i>if the array is too short to hold all the threads, the extra threads 1236 * are silently ignored.</i> If it is critical to obtain every active 1237 * thread in the current thread's thread group and its subgroups, the 1238 * invoker should verify that the returned int value is strictly less 1239 * than the length of {@code tarray}. 1240 * 1241 * <p> Due to the inherent race condition in this method, it is recommended 1242 * that the method only be used for debugging and monitoring purposes. 1243 * 1244 * @param tarray 1245 * an array into which to put the list of threads 1246 * 1247 * @return the number of threads put into the array 1248 * 1249 * @throws SecurityException 1250 * if {@link java.lang.ThreadGroup#checkAccess} determines that 1251 * the current thread cannot access its thread group 1252 */ 1253 public static int enumerate(Thread tarray[]) { 1254 return currentThread().getThreadGroup().enumerate(tarray); 1255 } 1256 1257 /** 1258 * Counts the number of stack frames in this thread. The thread must 1259 * be suspended. 1260 * 1261 * @return the number of stack frames in this thread. 1262 * @throws IllegalThreadStateException if this thread is not 1263 * suspended. 1264 * @deprecated The definition of this call depends on {@link #suspend}, 1265 * which is deprecated. Further, the results of this call 1266 * were never well-defined. 1267 * This method is subject to removal in a future version of Java SE. 1268 * @see StackWalker 1269 */ 1270 @Deprecated(since="1.2", forRemoval=true) 1271 public native int countStackFrames(); 1272 1273 /** 1274 * Waits at most {@code millis} milliseconds for this thread to 1275 * die. A timeout of {@code 0} means to wait forever. 1276 * 1277 * <p> This implementation uses a loop of {@code this.wait} calls 1278 * conditioned on {@code this.isAlive}. As a thread terminates the 1279 * {@code this.notifyAll} method is invoked. It is recommended that 1280 * applications not use {@code wait}, {@code notify}, or 1281 * {@code notifyAll} on {@code Thread} instances. 1282 * 1283 * @param millis 1284 * the time to wait in milliseconds 1285 * 1286 * @throws IllegalArgumentException 1287 * if the value of {@code millis} is negative 1288 * 1289 * @throws InterruptedException 1290 * if any thread has interrupted the current thread. The 1291 * <i>interrupted status</i> of the current thread is 1292 * cleared when this exception is thrown. 1293 */ 1294 public final synchronized void join(long millis) 1295 throws InterruptedException { 1296 long base = System.currentTimeMillis(); 1297 long now = 0; 1298 1299 if (millis < 0) { 1300 throw new IllegalArgumentException("timeout value is negative"); 1301 } 1302 1303 if (millis == 0) { 1304 while (isAlive()) { 1305 wait(0); 1306 } 1307 } else { 1308 while (isAlive()) { 1309 long delay = millis - now; 1310 if (delay <= 0) { 1311 break; 1312 } 1313 wait(delay); 1314 now = System.currentTimeMillis() - base; 1315 } 1316 } 1317 } 1318 1319 /** 1320 * Waits at most {@code millis} milliseconds plus 1321 * {@code nanos} nanoseconds for this thread to die. 1322 * 1323 * <p> This implementation uses a loop of {@code this.wait} calls 1324 * conditioned on {@code this.isAlive}. As a thread terminates the 1325 * {@code this.notifyAll} method is invoked. It is recommended that 1326 * applications not use {@code wait}, {@code notify}, or 1327 * {@code notifyAll} on {@code Thread} instances. 1328 * 1329 * @param millis 1330 * the time to wait in milliseconds 1331 * 1332 * @param nanos 1333 * {@code 0-999999} additional nanoseconds to wait 1334 * 1335 * @throws IllegalArgumentException 1336 * if the value of {@code millis} is negative, or the value 1337 * of {@code nanos} is not in the range {@code 0-999999} 1338 * 1339 * @throws InterruptedException 1340 * if any thread has interrupted the current thread. The 1341 * <i>interrupted status</i> of the current thread is 1342 * cleared when this exception is thrown. 1343 */ 1344 public final synchronized void join(long millis, int nanos) 1345 throws InterruptedException { 1346 1347 if (millis < 0) { 1348 throw new IllegalArgumentException("timeout value is negative"); 1349 } 1350 1351 if (nanos < 0 || nanos > 999999) { 1352 throw new IllegalArgumentException( 1353 "nanosecond timeout value out of range"); 1354 } 1355 1356 if (nanos >= 500000 || (nanos != 0 && millis == 0)) { 1357 millis++; 1358 } 1359 1360 join(millis); 1361 } 1362 1363 /** 1364 * Waits for this thread to die. 1365 * 1366 * <p> An invocation of this method behaves in exactly the same 1367 * way as the invocation 1368 * 1369 * <blockquote> 1370 * {@linkplain #join(long) join}{@code (0)} 1371 * </blockquote> 1372 * 1373 * @throws InterruptedException 1374 * if any thread has interrupted the current thread. The 1375 * <i>interrupted status</i> of the current thread is 1376 * cleared when this exception is thrown. 1377 */ 1378 public final void join() throws InterruptedException { 1379 join(0); 1380 } 1381 1382 /** 1383 * Prints a stack trace of the current thread to the standard error stream. 1384 * This method is used only for debugging. 1385 */ 1386 public static void dumpStack() { 1387 new Exception("Stack trace").printStackTrace(); 1388 } 1389 1390 /** 1391 * Marks this thread as either a {@linkplain #isDaemon daemon} thread 1392 * or a user thread. The Java Virtual Machine exits when the only 1393 * threads running are all daemon threads. 1394 * 1395 * <p> This method must be invoked before the thread is started. 1396 * 1397 * @param on 1398 * if {@code true}, marks this thread as a daemon thread 1399 * 1400 * @throws IllegalThreadStateException 1401 * if this thread is {@linkplain #isAlive alive} 1402 * 1403 * @throws SecurityException 1404 * if {@link #checkAccess} determines that the current 1405 * thread cannot modify this thread 1406 */ 1407 public final void setDaemon(boolean on) { 1408 checkAccess(); 1409 if (isAlive()) { 1410 throw new IllegalThreadStateException(); 1411 } 1412 daemon = on; 1413 } 1414 1415 /** 1416 * Tests if this thread is a daemon thread. 1417 * 1418 * @return {@code true} if this thread is a daemon thread; 1419 * {@code false} otherwise. 1420 * @see #setDaemon(boolean) 1421 */ 1422 public final boolean isDaemon() { 1423 return daemon; 1424 } 1425 1426 /** 1427 * Determines if the currently running thread has permission to 1428 * modify this thread. 1429 * <p> 1430 * If there is a security manager, its {@code checkAccess} method 1431 * is called with this thread as its argument. This may result in 1432 * throwing a {@code SecurityException}. 1433 * 1434 * @throws SecurityException if the current thread is not allowed to 1435 * access this thread. 1436 * @see SecurityManager#checkAccess(Thread) 1437 */ 1438 public final void checkAccess() { 1439 SecurityManager security = System.getSecurityManager(); 1440 if (security != null) { 1441 security.checkAccess(this); 1442 } 1443 } 1444 1445 /** 1446 * Returns a string representation of this thread, including the 1447 * thread's name, priority, and thread group. 1448 * 1449 * @return a string representation of this thread. 1450 */ 1451 public String toString() { 1452 ThreadGroup group = getThreadGroup(); 1453 if (group != null) { 1454 return "Thread[" + getName() + "," + getPriority() + "," + 1455 group.getName() + "]"; 1456 } else { 1457 return "Thread[" + getName() + "," + getPriority() + "," + 1458 "" + "]"; 1459 } 1460 } 1461 1462 /** 1463 * Returns the context {@code ClassLoader} for this thread. The context 1464 * {@code ClassLoader} is provided by the creator of the thread for use 1465 * by code running in this thread when loading classes and resources. 1466 * If not {@linkplain #setContextClassLoader set}, the default is the 1467 * {@code ClassLoader} context of the parent thread. The context 1468 * {@code ClassLoader} of the 1469 * primordial thread is typically set to the class loader used to load the 1470 * application. 1471 * 1472 * 1473 * @return the context {@code ClassLoader} for this thread, or {@code null} 1474 * indicating the system class loader (or, failing that, the 1475 * bootstrap class loader) 1476 * 1477 * @throws SecurityException 1478 * if a security manager is present, and the caller's class loader 1479 * is not {@code null} and is not the same as or an ancestor of the 1480 * context class loader, and the caller does not have the 1481 * {@link RuntimePermission}{@code ("getClassLoader")} 1482 * 1483 * @since 1.2 1484 */ 1485 @CallerSensitive 1486 public ClassLoader getContextClassLoader() { 1487 if (contextClassLoader == null) 1488 return null; 1489 SecurityManager sm = System.getSecurityManager(); 1490 if (sm != null) { 1491 ClassLoader.checkClassLoaderPermission(contextClassLoader, 1492 Reflection.getCallerClass()); 1493 } 1494 return contextClassLoader; 1495 } 1496 1497 /** 1498 * Sets the context ClassLoader for this Thread. The context 1499 * ClassLoader can be set when a thread is created, and allows 1500 * the creator of the thread to provide the appropriate class loader, 1501 * through {@code getContextClassLoader}, to code running in the thread 1502 * when loading classes and resources. 1503 * 1504 * <p>If a security manager is present, its {@link 1505 * SecurityManager#checkPermission(java.security.Permission) checkPermission} 1506 * method is invoked with a {@link RuntimePermission RuntimePermission}{@code 1507 * ("setContextClassLoader")} permission to see if setting the context 1508 * ClassLoader is permitted. 1509 * 1510 * @param cl 1511 * the context ClassLoader for this Thread, or null indicating the 1512 * system class loader (or, failing that, the bootstrap class loader) 1513 * 1514 * @throws SecurityException 1515 * if the current thread cannot set the context ClassLoader 1516 * 1517 * @since 1.2 1518 */ 1519 public void setContextClassLoader(ClassLoader cl) { 1520 SecurityManager sm = System.getSecurityManager(); 1521 if (sm != null) { 1522 sm.checkPermission(new RuntimePermission("setContextClassLoader")); 1523 } 1524 contextClassLoader = cl; 1525 } 1526 1527 /** 1528 * Returns {@code true} if and only if the current thread holds the 1529 * monitor lock on the specified object. 1530 * 1531 * <p>This method is designed to allow a program to assert that 1532 * the current thread already holds a specified lock: 1533 * <pre> 1534 * assert Thread.holdsLock(obj); 1535 * </pre> 1536 * 1537 * @param obj the object on which to test lock ownership 1538 * @throws NullPointerException if obj is {@code null} 1539 * @return {@code true} if the current thread holds the monitor lock on 1540 * the specified object. 1541 * @since 1.4 1542 */ 1543 public static native boolean holdsLock(Object obj); 1544 1545 private static final StackTraceElement[] EMPTY_STACK_TRACE 1546 = new StackTraceElement[0]; 1547 1548 /** 1549 * Returns an array of stack trace elements representing the stack dump 1550 * of this thread. This method will return a zero-length array if 1551 * this thread has not started, has started but has not yet been 1552 * scheduled to run by the system, or has terminated. 1553 * If the returned array is of non-zero length then the first element of 1554 * the array represents the top of the stack, which is the most recent 1555 * method invocation in the sequence. The last element of the array 1556 * represents the bottom of the stack, which is the least recent method 1557 * invocation in the sequence. 1558 * 1559 * <p>If there is a security manager, and this thread is not 1560 * the current thread, then the security manager's 1561 * {@code checkPermission} method is called with a 1562 * {@code RuntimePermission("getStackTrace")} permission 1563 * to see if it's ok to get the stack trace. 1564 * 1565 * <p>Some virtual machines may, under some circumstances, omit one 1566 * or more stack frames from the stack trace. In the extreme case, 1567 * a virtual machine that has no stack trace information concerning 1568 * this thread is permitted to return a zero-length array from this 1569 * method. 1570 * 1571 * @return an array of {@code StackTraceElement}, 1572 * each represents one stack frame. 1573 * 1574 * @throws SecurityException 1575 * if a security manager exists and its 1576 * {@code checkPermission} method doesn't allow 1577 * getting the stack trace of thread. 1578 * @see SecurityManager#checkPermission 1579 * @see RuntimePermission 1580 * @see Throwable#getStackTrace 1581 * 1582 * @since 1.5 1583 */ 1584 public StackTraceElement[] getStackTrace() { 1585 if (this != Thread.currentThread()) { 1586 // check for getStackTrace permission 1587 SecurityManager security = System.getSecurityManager(); 1588 if (security != null) { 1589 security.checkPermission( 1590 SecurityConstants.GET_STACK_TRACE_PERMISSION); 1591 } 1592 // optimization so we do not call into the vm for threads that 1593 // have not yet started or have terminated 1594 if (!isAlive()) { 1595 return EMPTY_STACK_TRACE; 1596 } 1597 StackTraceElement[][] stackTraceArray = dumpThreads(new Thread[] {this}); 1598 StackTraceElement[] stackTrace = stackTraceArray[0]; 1599 // a thread that was alive during the previous isAlive call may have 1600 // since terminated, therefore not having a stacktrace. 1601 if (stackTrace == null) { 1602 stackTrace = EMPTY_STACK_TRACE; 1603 } 1604 return stackTrace; 1605 } else { 1606 return (new Exception()).getStackTrace(); 1607 } 1608 } 1609 1610 /** 1611 * Returns a map of stack traces for all live threads. 1612 * The map keys are threads and each map value is an array of 1613 * {@code StackTraceElement} that represents the stack dump 1614 * of the corresponding {@code Thread}. 1615 * The returned stack traces are in the format specified for 1616 * the {@link #getStackTrace getStackTrace} method. 1617 * 1618 * <p>The threads may be executing while this method is called. 1619 * The stack trace of each thread only represents a snapshot and 1620 * each stack trace may be obtained at different time. A zero-length 1621 * array will be returned in the map value if the virtual machine has 1622 * no stack trace information about a thread. 1623 * 1624 * <p>If there is a security manager, then the security manager's 1625 * {@code checkPermission} method is called with a 1626 * {@code RuntimePermission("getStackTrace")} permission as well as 1627 * {@code RuntimePermission("modifyThreadGroup")} permission 1628 * to see if it is ok to get the stack trace of all threads. 1629 * 1630 * @return a {@code Map} from {@code Thread} to an array of 1631 * {@code StackTraceElement} that represents the stack trace of 1632 * the corresponding thread. 1633 * 1634 * @throws SecurityException 1635 * if a security manager exists and its 1636 * {@code checkPermission} method doesn't allow 1637 * getting the stack trace of thread. 1638 * @see #getStackTrace 1639 * @see SecurityManager#checkPermission 1640 * @see RuntimePermission 1641 * @see Throwable#getStackTrace 1642 * 1643 * @since 1.5 1644 */ 1645 public static Map<Thread, StackTraceElement[]> getAllStackTraces() { 1646 // check for getStackTrace permission 1647 SecurityManager security = System.getSecurityManager(); 1648 if (security != null) { 1649 security.checkPermission( 1650 SecurityConstants.GET_STACK_TRACE_PERMISSION); 1651 security.checkPermission( 1652 SecurityConstants.MODIFY_THREADGROUP_PERMISSION); 1653 } 1654 1655 // Get a snapshot of the list of all threads 1656 Thread[] threads = getThreads(); 1657 StackTraceElement[][] traces = dumpThreads(threads); 1658 Map<Thread, StackTraceElement[]> m = new HashMap<>(threads.length); 1659 for (int i = 0; i < threads.length; i++) { 1660 StackTraceElement[] stackTrace = traces[i]; 1661 if (stackTrace != null) { 1662 m.put(threads[i], stackTrace); 1663 } 1664 // else terminated so we don't put it in the map 1665 } 1666 return m; 1667 } 1668 1669 /** cache of subclass security audit results */ 1670 /* Replace with ConcurrentReferenceHashMap when/if it appears in a future 1671 * release */ 1672 private static class Caches { 1673 /** cache of subclass security audit results */ 1674 static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits = 1675 new ConcurrentHashMap<>(); 1676 1677 /** queue for WeakReferences to audited subclasses */ 1678 static final ReferenceQueue<Class<?>> subclassAuditsQueue = 1679 new ReferenceQueue<>(); 1680 } 1681 1682 /** 1683 * Verifies that this (possibly subclass) instance can be constructed 1684 * without violating security constraints: the subclass must not override 1685 * security-sensitive non-final methods, or else the 1686 * "enableContextClassLoaderOverride" RuntimePermission is checked. 1687 */ 1688 private static boolean isCCLOverridden(Class<?> cl) { 1689 if (cl == Thread.class) 1690 return false; 1691 1692 processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits); 1693 WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue); 1694 Boolean result = Caches.subclassAudits.get(key); 1695 if (result == null) { 1696 result = Boolean.valueOf(auditSubclass(cl)); 1697 Caches.subclassAudits.putIfAbsent(key, result); 1698 } 1699 1700 return result.booleanValue(); 1701 } 1702 1703 /** 1704 * Performs reflective checks on given subclass to verify that it doesn't 1705 * override security-sensitive non-final methods. Returns true if the 1706 * subclass overrides any of the methods, false otherwise. 1707 */ 1708 private static boolean auditSubclass(final Class<?> subcl) { 1709 Boolean result = AccessController.doPrivileged( 1710 new PrivilegedAction<>() { 1711 public Boolean run() { 1712 for (Class<?> cl = subcl; 1713 cl != Thread.class; 1714 cl = cl.getSuperclass()) 1715 { 1716 try { 1717 cl.getDeclaredMethod("getContextClassLoader", new Class<?>[0]); 1718 return Boolean.TRUE; 1719 } catch (NoSuchMethodException ex) { 1720 } 1721 try { 1722 Class<?>[] params = {ClassLoader.class}; 1723 cl.getDeclaredMethod("setContextClassLoader", params); 1724 return Boolean.TRUE; 1725 } catch (NoSuchMethodException ex) { 1726 } 1727 } 1728 return Boolean.FALSE; 1729 } 1730 } 1731 ); 1732 return result.booleanValue(); 1733 } 1734 1735 private static native StackTraceElement[][] dumpThreads(Thread[] threads); 1736 private static native Thread[] getThreads(); 1737 1738 /** 1739 * Returns the identifier of this Thread. The thread ID is a positive 1740 * {@code long} number generated when this thread was created. 1741 * The thread ID is unique and remains unchanged during its lifetime. 1742 * When a thread is terminated, this thread ID may be reused. 1743 * 1744 * @return this thread's ID. 1745 * @since 1.5 1746 */ 1747 public long getId() { 1748 return tid; 1749 } 1750 1751 /** 1752 * A thread state. A thread can be in one of the following states: 1753 * <ul> 1754 * <li>{@link #NEW}<br> 1755 * A thread that has not yet started is in this state. 1756 * </li> 1757 * <li>{@link #RUNNABLE}<br> 1758 * A thread executing in the Java virtual machine is in this state. 1759 * </li> 1760 * <li>{@link #BLOCKED}<br> 1761 * A thread that is blocked waiting for a monitor lock 1762 * is in this state. 1763 * </li> 1764 * <li>{@link #WAITING}<br> 1765 * A thread that is waiting indefinitely for another thread to 1766 * perform a particular action is in this state. 1767 * </li> 1768 * <li>{@link #TIMED_WAITING}<br> 1769 * A thread that is waiting for another thread to perform an action 1770 * for up to a specified waiting time is in this state. 1771 * </li> 1772 * <li>{@link #TERMINATED}<br> 1773 * A thread that has exited is in this state. 1774 * </li> 1775 * </ul> 1776 * 1777 * <p> 1778 * A thread can be in only one state at a given point in time. 1779 * These states are virtual machine states which do not reflect 1780 * any operating system thread states. 1781 * 1782 * @since 1.5 1783 * @see #getState 1784 */ 1785 public enum State { 1786 /** 1787 * Thread state for a thread which has not yet started. 1788 */ 1789 NEW, 1790 1791 /** 1792 * Thread state for a runnable thread. A thread in the runnable 1793 * state is executing in the Java virtual machine but it may 1794 * be waiting for other resources from the operating system 1795 * such as processor. 1796 */ 1797 RUNNABLE, 1798 1799 /** 1800 * Thread state for a thread blocked waiting for a monitor lock. 1801 * A thread in the blocked state is waiting for a monitor lock 1802 * to enter a synchronized block/method or 1803 * reenter a synchronized block/method after calling 1804 * {@link Object#wait() Object.wait}. 1805 */ 1806 BLOCKED, 1807 1808 /** 1809 * Thread state for a waiting thread. 1810 * A thread is in the waiting state due to calling one of the 1811 * following methods: 1812 * <ul> 1813 * <li>{@link Object#wait() Object.wait} with no timeout</li> 1814 * <li>{@link #join() Thread.join} with no timeout</li> 1815 * <li>{@link LockSupport#park() LockSupport.park}</li> 1816 * </ul> 1817 * 1818 * <p>A thread in the waiting state is waiting for another thread to 1819 * perform a particular action. 1820 * 1821 * For example, a thread that has called {@code Object.wait()} 1822 * on an object is waiting for another thread to call 1823 * {@code Object.notify()} or {@code Object.notifyAll()} on 1824 * that object. A thread that has called {@code Thread.join()} 1825 * is waiting for a specified thread to terminate. 1826 */ 1827 WAITING, 1828 1829 /** 1830 * Thread state for a waiting thread with a specified waiting time. 1831 * A thread is in the timed waiting state due to calling one of 1832 * the following methods with a specified positive waiting time: 1833 * <ul> 1834 * <li>{@link #sleep Thread.sleep}</li> 1835 * <li>{@link Object#wait(long) Object.wait} with timeout</li> 1836 * <li>{@link #join(long) Thread.join} with timeout</li> 1837 * <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li> 1838 * <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li> 1839 * </ul> 1840 */ 1841 TIMED_WAITING, 1842 1843 /** 1844 * Thread state for a terminated thread. 1845 * The thread has completed execution. 1846 */ 1847 TERMINATED; 1848 } 1849 1850 /** 1851 * Returns the state of this thread. 1852 * This method is designed for use in monitoring of the system state, 1853 * not for synchronization control. 1854 * 1855 * @return this thread's state. 1856 * @since 1.5 1857 */ 1858 public State getState() { 1859 // get current thread state 1860 return jdk.internal.misc.VM.toThreadState(threadStatus); 1861 } 1862 1863 // Added in JSR-166 1864 1865 /** 1866 * Interface for handlers invoked when a {@code Thread} abruptly 1867 * terminates due to an uncaught exception. 1868 * <p>When a thread is about to terminate due to an uncaught exception 1869 * the Java Virtual Machine will query the thread for its 1870 * {@code UncaughtExceptionHandler} using 1871 * {@link #getUncaughtExceptionHandler} and will invoke the handler's 1872 * {@code uncaughtException} method, passing the thread and the 1873 * exception as arguments. 1874 * If a thread has not had its {@code UncaughtExceptionHandler} 1875 * explicitly set, then its {@code ThreadGroup} object acts as its 1876 * {@code UncaughtExceptionHandler}. If the {@code ThreadGroup} object 1877 * has no 1878 * special requirements for dealing with the exception, it can forward 1879 * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler 1880 * default uncaught exception handler}. 1881 * 1882 * @see #setDefaultUncaughtExceptionHandler 1883 * @see #setUncaughtExceptionHandler 1884 * @see ThreadGroup#uncaughtException 1885 * @since 1.5 1886 */ 1887 @FunctionalInterface 1888 public interface UncaughtExceptionHandler { 1889 /** 1890 * Method invoked when the given thread terminates due to the 1891 * given uncaught exception. 1892 * <p>Any exception thrown by this method will be ignored by the 1893 * Java Virtual Machine. 1894 * @param t the thread 1895 * @param e the exception 1896 */ 1897 void uncaughtException(Thread t, Throwable e); 1898 } 1899 1900 // null unless explicitly set 1901 private volatile UncaughtExceptionHandler uncaughtExceptionHandler; 1902 1903 // null unless explicitly set 1904 private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler; 1905 1906 /** 1907 * Set the default handler invoked when a thread abruptly terminates 1908 * due to an uncaught exception, and no other handler has been defined 1909 * for that thread. 1910 * 1911 * <p>Uncaught exception handling is controlled first by the thread, then 1912 * by the thread's {@link ThreadGroup} object and finally by the default 1913 * uncaught exception handler. If the thread does not have an explicit 1914 * uncaught exception handler set, and the thread's thread group 1915 * (including parent thread groups) does not specialize its 1916 * {@code uncaughtException} method, then the default handler's 1917 * {@code uncaughtException} method will be invoked. 1918 * <p>By setting the default uncaught exception handler, an application 1919 * can change the way in which uncaught exceptions are handled (such as 1920 * logging to a specific device, or file) for those threads that would 1921 * already accept whatever "default" behavior the system 1922 * provided. 1923 * 1924 * <p>Note that the default uncaught exception handler should not usually 1925 * defer to the thread's {@code ThreadGroup} object, as that could cause 1926 * infinite recursion. 1927 * 1928 * @param eh the object to use as the default uncaught exception handler. 1929 * If {@code null} then there is no default handler. 1930 * 1931 * @throws SecurityException if a security manager is present and it denies 1932 * {@link RuntimePermission}{@code ("setDefaultUncaughtExceptionHandler")} 1933 * 1934 * @see #setUncaughtExceptionHandler 1935 * @see #getUncaughtExceptionHandler 1936 * @see ThreadGroup#uncaughtException 1937 * @since 1.5 1938 */ 1939 public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler eh) { 1940 SecurityManager sm = System.getSecurityManager(); 1941 if (sm != null) { 1942 sm.checkPermission( 1943 new RuntimePermission("setDefaultUncaughtExceptionHandler") 1944 ); 1945 } 1946 1947 defaultUncaughtExceptionHandler = eh; 1948 } 1949 1950 /** 1951 * Returns the default handler invoked when a thread abruptly terminates 1952 * due to an uncaught exception. If the returned value is {@code null}, 1953 * there is no default. 1954 * @since 1.5 1955 * @see #setDefaultUncaughtExceptionHandler 1956 * @return the default uncaught exception handler for all threads 1957 */ 1958 public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler(){ 1959 return defaultUncaughtExceptionHandler; 1960 } 1961 1962 /** 1963 * Returns the handler invoked when this thread abruptly terminates 1964 * due to an uncaught exception. If this thread has not had an 1965 * uncaught exception handler explicitly set then this thread's 1966 * {@code ThreadGroup} object is returned, unless this thread 1967 * has terminated, in which case {@code null} is returned. 1968 * @since 1.5 1969 * @return the uncaught exception handler for this thread 1970 */ 1971 public UncaughtExceptionHandler getUncaughtExceptionHandler() { 1972 return uncaughtExceptionHandler != null ? 1973 uncaughtExceptionHandler : group; 1974 } 1975 1976 /** 1977 * Set the handler invoked when this thread abruptly terminates 1978 * due to an uncaught exception. 1979 * <p>A thread can take full control of how it responds to uncaught 1980 * exceptions by having its uncaught exception handler explicitly set. 1981 * If no such handler is set then the thread's {@code ThreadGroup} 1982 * object acts as its handler. 1983 * @param eh the object to use as this thread's uncaught exception 1984 * handler. If {@code null} then this thread has no explicit handler. 1985 * @throws SecurityException if the current thread is not allowed to 1986 * modify this thread. 1987 * @see #setDefaultUncaughtExceptionHandler 1988 * @see ThreadGroup#uncaughtException 1989 * @since 1.5 1990 */ 1991 public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh) { 1992 checkAccess(); 1993 uncaughtExceptionHandler = eh; 1994 } 1995 1996 /** 1997 * Dispatch an uncaught exception to the handler. This method is 1998 * intended to be called only by the JVM. 1999 */ 2000 private void dispatchUncaughtException(Throwable e) { 2001 getUncaughtExceptionHandler().uncaughtException(this, e); 2002 } 2003 2004 /** 2005 * Removes from the specified map any keys that have been enqueued 2006 * on the specified reference queue. 2007 */ 2008 static void processQueue(ReferenceQueue<Class<?>> queue, 2009 ConcurrentMap<? extends 2010 WeakReference<Class<?>>, ?> map) 2011 { 2012 Reference<? extends Class<?>> ref; 2013 while((ref = queue.poll()) != null) { 2014 map.remove(ref); 2015 } 2016 } 2017 2018 /** 2019 * Weak key for Class objects. 2020 **/ 2021 static class WeakClassKey extends WeakReference<Class<?>> { 2022 /** 2023 * saved value of the referent's identity hash code, to maintain 2024 * a consistent hash code after the referent has been cleared 2025 */ 2026 private final int hash; 2027 2028 /** 2029 * Create a new WeakClassKey to the given object, registered 2030 * with a queue. 2031 */ 2032 WeakClassKey(Class<?> cl, ReferenceQueue<Class<?>> refQueue) { 2033 super(cl, refQueue); 2034 hash = System.identityHashCode(cl); 2035 } 2036 2037 /** 2038 * Returns the identity hash code of the original referent. 2039 */ 2040 @Override 2041 public int hashCode() { 2042 return hash; 2043 } 2044 2045 /** 2046 * Returns true if the given object is this identical 2047 * WeakClassKey instance, or, if this object's referent has not 2048 * been cleared, if the given object is another WeakClassKey 2049 * instance with the identical non-null referent as this one. 2050 */ 2051 @Override 2052 public boolean equals(Object obj) { 2053 if (obj == this) 2054 return true; 2055 2056 if (obj instanceof WeakClassKey) { 2057 Object referent = get(); 2058 return (referent != null) && 2059 (referent == ((WeakClassKey) obj).get()); 2060 } else { 2061 return false; 2062 } 2063 } 2064 } 2065 2066 2067 // The following three initially uninitialized fields are exclusively 2068 // managed by class java.util.concurrent.ThreadLocalRandom. These 2069 // fields are used to build the high-performance PRNGs in the 2070 // concurrent code, and we can not risk accidental false sharing. 2071 // Hence, the fields are isolated with @Contended. 2072 2073 /** The current seed for a ThreadLocalRandom */ 2074 @jdk.internal.vm.annotation.Contended("tlr") 2075 long threadLocalRandomSeed; 2076 2077 /** Probe hash value; nonzero if threadLocalRandomSeed initialized */ 2078 @jdk.internal.vm.annotation.Contended("tlr") 2079 int threadLocalRandomProbe; 2080 2081 /** Secondary seed isolated from public ThreadLocalRandom sequence */ 2082 @jdk.internal.vm.annotation.Contended("tlr") 2083 int threadLocalRandomSecondarySeed; 2084 2085 /* Some private helper methods */ 2086 private native void setPriority0(int newPriority); 2087 private native void stop0(Object o); 2088 private native void suspend0(); 2089 private native void resume0(); 2090 private native void interrupt0(); 2091 private native void setNativeName(String name); 2092 }