1 /* 2 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.lang; 27 28 import java.lang.ref.Reference; 29 import java.lang.ref.ReferenceQueue; 30 import java.lang.ref.WeakReference; 31 import java.security.AccessController; 32 import java.security.AccessControlContext; 33 import java.security.PrivilegedAction; 34 import java.util.Map; 35 import java.util.HashMap; 36 import java.util.concurrent.ConcurrentHashMap; 37 import java.util.concurrent.ConcurrentMap; 38 import java.util.concurrent.locks.LockSupport; 39 import sun.nio.ch.Interruptible; 40 import jdk.internal.reflect.CallerSensitive; 41 import jdk.internal.reflect.Reflection; 42 import sun.security.util.SecurityConstants; 43 import jdk.internal.HotSpotIntrinsicCandidate; 44 45 /** 46 * A <i>thread</i> is a thread of execution in a program. The Java 47 * Virtual Machine allows an application to have multiple threads of 48 * execution running concurrently. 49 * <p> 50 * Every thread has a priority. Threads with higher priority are 51 * executed in preference to threads with lower priority. Each thread 52 * may or may not also be marked as a daemon. When code running in 53 * some thread creates a new <code>Thread</code> object, the new 54 * thread has its priority initially set equal to the priority of the 55 * creating thread, and is a daemon thread if and only if the 56 * creating thread is a daemon. 57 * <p> 58 * When a Java Virtual Machine starts up, there is usually a single 59 * non-daemon thread (which typically calls the method named 60 * <code>main</code> of some designated class). The Java Virtual 61 * Machine continues to execute threads until either of the following 62 * occurs: 63 * <ul> 64 * <li>The <code>exit</code> method of class <code>Runtime</code> has been 65 * called and the security manager has permitted the exit operation 66 * to take place. 67 * <li>All threads that are not daemon threads have died, either by 68 * returning from the call to the <code>run</code> method or by 69 * throwing an exception that propagates beyond the <code>run</code> 70 * method. 71 * </ul> 72 * <p> 73 * There are two ways to create a new thread of execution. One is to 74 * declare a class to be a subclass of <code>Thread</code>. This 75 * subclass should override the <code>run</code> method of class 76 * <code>Thread</code>. An instance of the subclass can then be 77 * allocated and started. For example, a thread that computes primes 78 * larger than a stated value could be written as follows: 79 * <hr><blockquote><pre> 80 * class PrimeThread extends Thread { 81 * long minPrime; 82 * PrimeThread(long minPrime) { 83 * this.minPrime = minPrime; 84 * } 85 * 86 * public void run() { 87 * // compute primes larger than minPrime 88 * . . . 89 * } 90 * } 91 * </pre></blockquote><hr> 92 * <p> 93 * The following code would then create a thread and start it running: 94 * <blockquote><pre> 95 * PrimeThread p = new PrimeThread(143); 96 * p.start(); 97 * </pre></blockquote> 98 * <p> 99 * The other way to create a thread is to declare a class that 100 * implements the <code>Runnable</code> interface. That class then 101 * implements the <code>run</code> method. An instance of the class can 102 * then be allocated, passed as an argument when creating 103 * <code>Thread</code>, and started. The same example in this other 104 * style looks like the following: 105 * <hr><blockquote><pre> 106 * class PrimeRun implements Runnable { 107 * long minPrime; 108 * PrimeRun(long minPrime) { 109 * this.minPrime = minPrime; 110 * } 111 * 112 * public void run() { 113 * // compute primes larger than minPrime 114 * . . . 115 * } 116 * } 117 * </pre></blockquote><hr> 118 * <p> 119 * The following code would then create a thread and start it running: 120 * <blockquote><pre> 121 * PrimeRun p = new PrimeRun(143); 122 * new Thread(p).start(); 123 * </pre></blockquote> 124 * <p> 125 * Every thread has a name for identification purposes. More than 126 * one thread may have the same name. If a name is not specified when 127 * a thread is created, a new name is generated for it. 128 * <p> 129 * Unless otherwise noted, passing a {@code null} argument to a constructor 130 * or method in this class will cause a {@link NullPointerException} to be 131 * thrown. 132 * 133 * @author unascribed 134 * @see Runnable 135 * @see Runtime#exit(int) 136 * @see #run() 137 * @see #stop() 138 * @since 1.0 139 */ 140 public 141 class Thread implements Runnable { 142 /* Make sure registerNatives is the first thing <clinit> does. */ 143 private static native void registerNatives(); 144 static { 145 registerNatives(); 146 } 147 148 private volatile String name; 149 private int priority; 150 private Thread threadQ; 151 private long eetop; 152 153 /* Whether or not to single_step this thread. */ 154 private boolean single_step; 155 156 /* Whether or not the thread is a daemon thread. */ 157 private boolean daemon = false; 158 159 /* JVM state */ 160 private boolean stillborn = false; 161 162 /* What will be run. */ 163 private Runnable target; 164 165 /* The group of this thread */ 166 private ThreadGroup group; 167 168 /* The context ClassLoader for this thread */ 169 private ClassLoader contextClassLoader; 170 171 /* The inherited AccessControlContext of this thread */ 172 private AccessControlContext inheritedAccessControlContext; 173 174 /* For autonumbering anonymous threads. */ 175 private static int threadInitNumber; 176 private static synchronized int nextThreadNum() { 177 return threadInitNumber++; 178 } 179 180 /* ThreadLocal values pertaining to this thread. This map is maintained 181 * by the ThreadLocal class. */ 182 ThreadLocal.ThreadLocalMap threadLocals = null; 183 184 /* 185 * InheritableThreadLocal values pertaining to this thread. This map is 186 * maintained by the InheritableThreadLocal class. 187 */ 188 ThreadLocal.ThreadLocalMap inheritableThreadLocals = null; 189 190 /* 191 * The requested stack size for this thread, or 0 if the creator did 192 * not specify a stack size. It is up to the VM to do whatever it 193 * likes with this number; some VMs will ignore it. 194 */ 195 private long stackSize; 196 197 /* 198 * JVM-private state that persists after native thread termination. 199 */ 200 private long nativeParkEventPointer; 201 202 /* 203 * Thread ID 204 */ 205 private long tid; 206 207 /* For generating thread ID */ 208 private static long threadSeqNumber; 209 210 /* 211 * Java thread status for tools, default indicates thread 'not yet started' 212 */ 213 private volatile int threadStatus; 214 215 private static synchronized long nextThreadID() { 216 return ++threadSeqNumber; 217 } 218 219 /** 220 * The argument supplied to the current call to 221 * java.util.concurrent.locks.LockSupport.park. 222 * Set by (private) java.util.concurrent.locks.LockSupport.setBlocker 223 * Accessed using java.util.concurrent.locks.LockSupport.getBlocker 224 */ 225 volatile Object parkBlocker; 226 227 /* The object in which this thread is blocked in an interruptible I/O 228 * operation, if any. The blocker's interrupt method should be invoked 229 * after setting this thread's interrupt status. 230 */ 231 private volatile Interruptible blocker; 232 private final Object blockerLock = new Object(); 233 234 /* Set the blocker field; invoked via jdk.internal.misc.SharedSecrets 235 * from java.nio code 236 */ 237 void blockedOn(Interruptible b) { 238 synchronized (blockerLock) { 239 blocker = b; 240 } 241 } 242 243 /** 244 * The minimum priority that a thread can have. 245 */ 246 public static final int MIN_PRIORITY = 1; 247 248 /** 249 * The default priority that is assigned to a thread. 250 */ 251 public static final int NORM_PRIORITY = 5; 252 253 /** 254 * The maximum priority that a thread can have. 255 */ 256 public static final int MAX_PRIORITY = 10; 257 258 /** 259 * Returns a reference to the currently executing thread object. 260 * 261 * @return the currently executing thread. 262 */ 263 @HotSpotIntrinsicCandidate 264 public static native Thread currentThread(); 265 266 /** 267 * A hint to the scheduler that the current thread is willing to yield 268 * its current use of a processor. The scheduler is free to ignore this 269 * hint. 270 * 271 * <p> Yield is a heuristic attempt to improve relative progression 272 * between threads that would otherwise over-utilise a CPU. Its use 273 * should be combined with detailed profiling and benchmarking to 274 * ensure that it actually has the desired effect. 275 * 276 * <p> It is rarely appropriate to use this method. It may be useful 277 * for debugging or testing purposes, where it may help to reproduce 278 * bugs due to race conditions. It may also be useful when designing 279 * concurrency control constructs such as the ones in the 280 * {@link java.util.concurrent.locks} package. 281 */ 282 public static native void yield(); 283 284 /** 285 * Causes the currently executing thread to sleep (temporarily cease 286 * execution) for the specified number of milliseconds, subject to 287 * the precision and accuracy of system timers and schedulers. The thread 288 * does not lose ownership of any monitors. 289 * 290 * @param millis 291 * the length of time to sleep in milliseconds 292 * 293 * @throws IllegalArgumentException 294 * if the value of {@code millis} is negative 295 * 296 * @throws InterruptedException 297 * if any thread has interrupted the current thread. The 298 * <i>interrupted status</i> of the current thread is 299 * cleared when this exception is thrown. 300 */ 301 public static native void sleep(long millis) throws InterruptedException; 302 303 /** 304 * Causes the currently executing thread to sleep (temporarily cease 305 * execution) for the specified number of milliseconds plus the specified 306 * number of nanoseconds, subject to the precision and accuracy of system 307 * timers and schedulers. The thread does not lose ownership of any 308 * monitors. 309 * 310 * @param millis 311 * the length of time to sleep in milliseconds 312 * 313 * @param nanos 314 * {@code 0-999999} additional nanoseconds to sleep 315 * 316 * @throws IllegalArgumentException 317 * if the value of {@code millis} is negative, or the value of 318 * {@code nanos} is not in the range {@code 0-999999} 319 * 320 * @throws InterruptedException 321 * if any thread has interrupted the current thread. The 322 * <i>interrupted status</i> of the current thread is 323 * cleared when this exception is thrown. 324 */ 325 public static void sleep(long millis, int nanos) 326 throws InterruptedException { 327 if (millis < 0) { 328 throw new IllegalArgumentException("timeout value is negative"); 329 } 330 331 if (nanos < 0 || nanos > 999999) { 332 throw new IllegalArgumentException( 333 "nanosecond timeout value out of range"); 334 } 335 336 if (nanos >= 500000 || (nanos != 0 && millis == 0)) { 337 millis++; 338 } 339 340 sleep(millis); 341 } 342 343 /** 344 * Indicates that the caller is momentarily unable to progress, until the 345 * occurrence of one or more actions on the part of other activities. By 346 * invoking this method within each iteration of a spin-wait loop construct, 347 * the calling thread indicates to the runtime that it is busy-waiting. 348 * The runtime may take action to improve the performance of invoking 349 * spin-wait loop constructions. 350 * <p> 351 * @apiNote 352 * As an example consider a method in a class that spins in a loop until 353 * some flag is set outside of that method. A call to the {@code onSpinWait} 354 * method should be placed inside the spin loop. 355 * <pre>{@code 356 * class EventHandler { 357 * volatile boolean eventNotificationNotReceived; 358 * void waitForEventAndHandleIt() { 359 * while ( eventNotificationNotReceived ) { 360 * java.lang.Thread.onSpinWait(); 361 * } 362 * readAndProcessEvent(); 363 * } 364 * 365 * void readAndProcessEvent() { 366 * // Read event from some source and process it 367 * . . . 368 * } 369 * } 370 * }</pre> 371 * <p> 372 * The code above would remain correct even if the {@code onSpinWait} 373 * method was not called at all. However on some architectures the Java 374 * Virtual Machine may issue the processor instructions to address such 375 * code patterns in a more beneficial way. 376 * <p> 377 * @since 9 378 */ 379 @HotSpotIntrinsicCandidate 380 public static void onSpinWait() {} 381 382 /** 383 * Initializes a Thread with the current AccessControlContext. 384 * @see #init(ThreadGroup,Runnable,String,long,AccessControlContext,boolean) 385 */ 386 private void init(ThreadGroup g, Runnable target, String name, 387 long stackSize) { 388 init(g, target, name, stackSize, null, true); 389 } 390 391 /** 392 * Initializes a Thread. 393 * 394 * @param g the Thread group 395 * @param target the object whose run() method gets called 396 * @param name the name of the new Thread 397 * @param stackSize the desired stack size for the new thread, or 398 * zero to indicate that this parameter is to be ignored. 399 * @param acc the AccessControlContext to inherit, or 400 * AccessController.getContext() if null 401 * @param inheritThreadLocals if {@code true}, inherit initial values for 402 * inheritable thread-locals from the constructing thread 403 */ 404 private void init(ThreadGroup g, Runnable target, String name, 405 long stackSize, AccessControlContext acc, 406 boolean inheritThreadLocals) { 407 if (name == null) { 408 throw new NullPointerException("name cannot be null"); 409 } 410 411 this.name = name; 412 413 Thread parent = currentThread(); 414 SecurityManager security = System.getSecurityManager(); 415 if (g == null) { 416 /* Determine if it's an applet or not */ 417 418 /* If there is a security manager, ask the security manager 419 what to do. */ 420 if (security != null) { 421 g = security.getThreadGroup(); 422 } 423 424 /* If the security doesn't have a strong opinion of the matter 425 use the parent thread group. */ 426 if (g == null) { 427 g = parent.getThreadGroup(); 428 } 429 } 430 431 /* checkAccess regardless of whether or not threadgroup is 432 explicitly passed in. */ 433 g.checkAccess(); 434 435 /* 436 * Do we have the required permissions? 437 */ 438 if (security != null) { 439 if (isCCLOverridden(getClass())) { 440 security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION); 441 } 442 } 443 444 g.addUnstarted(); 445 446 this.group = g; 447 this.daemon = parent.isDaemon(); 448 this.priority = parent.getPriority(); 449 if (security == null || isCCLOverridden(parent.getClass())) 450 this.contextClassLoader = parent.getContextClassLoader(); 451 else 452 this.contextClassLoader = parent.contextClassLoader; 453 this.inheritedAccessControlContext = 454 acc != null ? acc : AccessController.getContext(); 455 this.target = target; 456 setPriority(priority); 457 if (inheritThreadLocals && parent.inheritableThreadLocals != null) 458 this.inheritableThreadLocals = 459 ThreadLocal.createInheritedMap(parent.inheritableThreadLocals); 460 /* Stash the specified stack size in case the VM cares */ 461 this.stackSize = stackSize; 462 463 /* Set thread ID */ 464 tid = nextThreadID(); 465 } 466 467 /** 468 * Throws CloneNotSupportedException as a Thread can not be meaningfully 469 * cloned. Construct a new Thread instead. 470 * 471 * @throws CloneNotSupportedException 472 * always 473 */ 474 @Override 475 protected Object clone() throws CloneNotSupportedException { 476 throw new CloneNotSupportedException(); 477 } 478 479 /** 480 * Allocates a new {@code Thread} object. This constructor has the same 481 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 482 * {@code (null, null, gname)}, where {@code gname} is a newly generated 483 * name. Automatically generated names are of the form 484 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer. 485 */ 486 public Thread() { 487 init(null, null, "Thread-" + nextThreadNum(), 0); 488 } 489 490 /** 491 * Allocates a new {@code Thread} object. This constructor has the same 492 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 493 * {@code (null, target, gname)}, where {@code gname} is a newly generated 494 * name. Automatically generated names are of the form 495 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer. 496 * 497 * @param target 498 * the object whose {@code run} method is invoked when this thread 499 * is started. If {@code null}, this classes {@code run} method does 500 * nothing. 501 */ 502 public Thread(Runnable target) { 503 init(null, target, "Thread-" + nextThreadNum(), 0); 504 } 505 506 /** 507 * Creates a new Thread that inherits the given AccessControlContext. 508 * This is not a public constructor. 509 */ 510 Thread(Runnable target, AccessControlContext acc) { 511 init(null, target, "Thread-" + nextThreadNum(), 0, acc, true); 512 } 513 514 /** 515 * Allocates a new {@code Thread} object. This constructor has the same 516 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 517 * {@code (group, target, gname)} ,where {@code gname} is a newly generated 518 * name. Automatically generated names are of the form 519 * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer. 520 * 521 * @param group 522 * the thread group. If {@code null} and there is a security 523 * manager, the group is determined by {@linkplain 524 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. 525 * If there is not a security manager or {@code 526 * SecurityManager.getThreadGroup()} returns {@code null}, the group 527 * is set to the current thread's thread group. 528 * 529 * @param target 530 * the object whose {@code run} method is invoked when this thread 531 * is started. If {@code null}, this thread's run method is invoked. 532 * 533 * @throws SecurityException 534 * if the current thread cannot create a thread in the specified 535 * thread group 536 */ 537 public Thread(ThreadGroup group, Runnable target) { 538 init(group, target, "Thread-" + nextThreadNum(), 0); 539 } 540 541 /** 542 * Allocates a new {@code Thread} object. This constructor has the same 543 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 544 * {@code (null, null, name)}. 545 * 546 * @param name 547 * the name of the new thread 548 */ 549 public Thread(String name) { 550 init(null, null, name, 0); 551 } 552 553 /** 554 * Allocates a new {@code Thread} object. This constructor has the same 555 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 556 * {@code (group, null, name)}. 557 * 558 * @param group 559 * the thread group. If {@code null} and there is a security 560 * manager, the group is determined by {@linkplain 561 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. 562 * If there is not a security manager or {@code 563 * SecurityManager.getThreadGroup()} returns {@code null}, the group 564 * is set to the current thread's thread group. 565 * 566 * @param name 567 * the name of the new thread 568 * 569 * @throws SecurityException 570 * if the current thread cannot create a thread in the specified 571 * thread group 572 */ 573 public Thread(ThreadGroup group, String name) { 574 init(group, null, name, 0); 575 } 576 577 /** 578 * Allocates a new {@code Thread} object. This constructor has the same 579 * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} 580 * {@code (null, target, name)}. 581 * 582 * @param target 583 * the object whose {@code run} method is invoked when this thread 584 * is started. If {@code null}, this thread's run method is invoked. 585 * 586 * @param name 587 * the name of the new thread 588 */ 589 public Thread(Runnable target, String name) { 590 init(null, target, name, 0); 591 } 592 593 /** 594 * Allocates a new {@code Thread} object so that it has {@code target} 595 * as its run object, has the specified {@code name} as its name, 596 * and belongs to the thread group referred to by {@code group}. 597 * 598 * <p>If there is a security manager, its 599 * {@link SecurityManager#checkAccess(ThreadGroup) checkAccess} 600 * method is invoked with the ThreadGroup as its argument. 601 * 602 * <p>In addition, its {@code checkPermission} method is invoked with 603 * the {@code RuntimePermission("enableContextClassLoaderOverride")} 604 * permission when invoked directly or indirectly by the constructor 605 * of a subclass which overrides the {@code getContextClassLoader} 606 * or {@code setContextClassLoader} methods. 607 * 608 * <p>The priority of the newly created thread is set equal to the 609 * priority of the thread creating it, that is, the currently running 610 * thread. The method {@linkplain #setPriority setPriority} may be 611 * used to change the priority to a new value. 612 * 613 * <p>The newly created thread is initially marked as being a daemon 614 * thread if and only if the thread creating it is currently marked 615 * as a daemon thread. The method {@linkplain #setDaemon setDaemon} 616 * may be used to change whether or not a thread is a daemon. 617 * 618 * @param group 619 * the thread group. If {@code null} and there is a security 620 * manager, the group is determined by {@linkplain 621 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. 622 * If there is not a security manager or {@code 623 * SecurityManager.getThreadGroup()} returns {@code null}, the group 624 * is set to the current thread's thread group. 625 * 626 * @param target 627 * the object whose {@code run} method is invoked when this thread 628 * is started. If {@code null}, this thread's run method is invoked. 629 * 630 * @param name 631 * the name of the new thread 632 * 633 * @throws SecurityException 634 * if the current thread cannot create a thread in the specified 635 * thread group or cannot override the context class loader methods. 636 */ 637 public Thread(ThreadGroup group, Runnable target, String name) { 638 init(group, target, name, 0); 639 } 640 641 /** 642 * Allocates a new {@code Thread} object so that it has {@code target} 643 * as its run object, has the specified {@code name} as its name, 644 * and belongs to the thread group referred to by {@code group}, and has 645 * the specified <i>stack size</i>. 646 * 647 * <p>This constructor is identical to {@link 648 * #Thread(ThreadGroup,Runnable,String)} with the exception of the fact 649 * that it allows the thread stack size to be specified. The stack size 650 * is the approximate number of bytes of address space that the virtual 651 * machine is to allocate for this thread's stack. <b>The effect of the 652 * {@code stackSize} parameter, if any, is highly platform dependent.</b> 653 * 654 * <p>On some platforms, specifying a higher value for the 655 * {@code stackSize} parameter may allow a thread to achieve greater 656 * recursion depth before throwing a {@link StackOverflowError}. 657 * Similarly, specifying a lower value may allow a greater number of 658 * threads to exist concurrently without throwing an {@link 659 * OutOfMemoryError} (or other internal error). The details of 660 * the relationship between the value of the {@code stackSize} parameter 661 * and the maximum recursion depth and concurrency level are 662 * platform-dependent. <b>On some platforms, the value of the 663 * {@code stackSize} parameter may have no effect whatsoever.</b> 664 * 665 * <p>The virtual machine is free to treat the {@code stackSize} 666 * parameter as a suggestion. If the specified value is unreasonably low 667 * for the platform, the virtual machine may instead use some 668 * platform-specific minimum value; if the specified value is unreasonably 669 * high, the virtual machine may instead use some platform-specific 670 * maximum. Likewise, the virtual machine is free to round the specified 671 * value up or down as it sees fit (or to ignore it completely). 672 * 673 * <p>Specifying a value of zero for the {@code stackSize} parameter will 674 * cause this constructor to behave exactly like the 675 * {@code Thread(ThreadGroup, Runnable, String)} constructor. 676 * 677 * <p><i>Due to the platform-dependent nature of the behavior of this 678 * constructor, extreme care should be exercised in its use. 679 * The thread stack size necessary to perform a given computation will 680 * likely vary from one JRE implementation to another. In light of this 681 * variation, careful tuning of the stack size parameter may be required, 682 * and the tuning may need to be repeated for each JRE implementation on 683 * which an application is to run.</i> 684 * 685 * <p>Implementation note: Java platform implementers are encouraged to 686 * document their implementation's behavior with respect to the 687 * {@code stackSize} parameter. 688 * 689 * 690 * @param group 691 * the thread group. If {@code null} and there is a security 692 * manager, the group is determined by {@linkplain 693 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. 694 * If there is not a security manager or {@code 695 * SecurityManager.getThreadGroup()} returns {@code null}, the group 696 * is set to the current thread's thread group. 697 * 698 * @param target 699 * the object whose {@code run} method is invoked when this thread 700 * is started. If {@code null}, this thread's run method is invoked. 701 * 702 * @param name 703 * the name of the new thread 704 * 705 * @param stackSize 706 * the desired stack size for the new thread, or zero to indicate 707 * that this parameter is to be ignored. 708 * 709 * @throws SecurityException 710 * if the current thread cannot create a thread in the specified 711 * thread group 712 * 713 * @since 1.4 714 */ 715 public Thread(ThreadGroup group, Runnable target, String name, 716 long stackSize) { 717 init(group, target, name, stackSize); 718 } 719 720 /** 721 * Allocates a new {@code Thread} object so that it has {@code target} 722 * as its run object, has the specified {@code name} as its name, 723 * belongs to the thread group referred to by {@code group}, has 724 * the specified {@code stackSize}, and inherits initial values for 725 * {@linkplain InheritableThreadLocal inheritable thread-local} variables 726 * if {@code inheritThreadLocals} is {@code true}. 727 * 728 * <p> This constructor is identical to {@link 729 * #Thread(ThreadGroup,Runnable,String,long)} with the added ability to 730 * suppress, or not, the inheriting of initial values for inheritable 731 * thread-local variables from the constructing thread. This allows for 732 * finer grain control over inheritable thread-locals. Care must be taken 733 * when passing a value of {@code false} for {@code inheritThreadLocals}, 734 * as it may lead to unexpected behavior if the new thread executes code 735 * that expects a specific thread-local value to be inherited. 736 * 737 * <p> Specifying a value of {@code true} for the {@code inheritThreadLocals} 738 * parameter will cause this constructor to behave exactly like the 739 * {@code Thread(ThreadGroup, Runnable, String, long)} constructor. 740 * 741 * @param group 742 * the thread group. If {@code null} and there is a security 743 * manager, the group is determined by {@linkplain 744 * SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. 745 * If there is not a security manager or {@code 746 * SecurityManager.getThreadGroup()} returns {@code null}, the group 747 * is set to the current thread's thread group. 748 * 749 * @param target 750 * the object whose {@code run} method is invoked when this thread 751 * is started. If {@code null}, this thread's run method is invoked. 752 * 753 * @param name 754 * the name of the new thread 755 * 756 * @param stackSize 757 * the desired stack size for the new thread, or zero to indicate 758 * that this parameter is to be ignored 759 * 760 * @param inheritThreadLocals 761 * if {@code true}, inherit initial values for inheritable 762 * thread-locals from the constructing thread, otherwise no initial 763 * values are inherited 764 * 765 * @throws SecurityException 766 * if the current thread cannot create a thread in the specified 767 * thread group 768 * 769 * @since 9 770 */ 771 public Thread(ThreadGroup group, Runnable target, String name, 772 long stackSize, boolean inheritThreadLocals) { 773 init(group, target, name, stackSize, null, inheritThreadLocals); 774 } 775 776 /** 777 * Causes this thread to begin execution; the Java Virtual Machine 778 * calls the <code>run</code> method of this thread. 779 * <p> 780 * The result is that two threads are running concurrently: the 781 * current thread (which returns from the call to the 782 * <code>start</code> method) and the other thread (which executes its 783 * <code>run</code> method). 784 * <p> 785 * It is never legal to start a thread more than once. 786 * In particular, a thread may not be restarted once it has completed 787 * execution. 788 * 789 * @exception IllegalThreadStateException if the thread was already 790 * started. 791 * @see #run() 792 * @see #stop() 793 */ 794 public synchronized void start() { 795 /** 796 * This method is not invoked for the main method thread or "system" 797 * group threads created/set up by the VM. Any new functionality added 798 * to this method in the future may have to also be added to the VM. 799 * 800 * A zero status value corresponds to state "NEW". 801 */ 802 if (threadStatus != 0) 803 throw new IllegalThreadStateException(); 804 805 /* Notify the group that this thread is about to be started 806 * so that it can be added to the group's list of threads 807 * and the group's unstarted count can be decremented. */ 808 group.add(this); 809 810 boolean started = false; 811 try { 812 start0(); 813 started = true; 814 } finally { 815 try { 816 if (!started) { 817 group.threadStartFailed(this); 818 } 819 } catch (Throwable ignore) { 820 /* do nothing. If start0 threw a Throwable then 821 it will be passed up the call stack */ 822 } 823 } 824 } 825 826 private native void start0(); 827 828 /** 829 * If this thread was constructed using a separate 830 * <code>Runnable</code> run object, then that 831 * <code>Runnable</code> object's <code>run</code> method is called; 832 * otherwise, this method does nothing and returns. 833 * <p> 834 * Subclasses of <code>Thread</code> should override this method. 835 * 836 * @see #start() 837 * @see #stop() 838 * @see #Thread(ThreadGroup, Runnable, String) 839 */ 840 @Override 841 public void run() { 842 if (target != null) { 843 target.run(); 844 } 845 } 846 847 /** 848 * This method is called by the system to give a Thread 849 * a chance to clean up before it actually exits. 850 */ 851 private void exit() { 852 if (group != null) { 853 group.threadTerminated(this); 854 group = null; 855 } 856 /* Aggressively null out all reference fields: see bug 4006245 */ 857 target = null; 858 /* Speed the release of some of these resources */ 859 threadLocals = null; 860 inheritableThreadLocals = null; 861 inheritedAccessControlContext = null; 862 blocker = null; 863 uncaughtExceptionHandler = null; 864 } 865 866 /** 867 * Forces the thread to stop executing. 868 * <p> 869 * If there is a security manager installed, its <code>checkAccess</code> 870 * method is called with <code>this</code> 871 * as its argument. This may result in a 872 * <code>SecurityException</code> being raised (in the current thread). 873 * <p> 874 * If this thread is different from the current thread (that is, the current 875 * thread is trying to stop a thread other than itself), the 876 * security manager's <code>checkPermission</code> method (with a 877 * <code>RuntimePermission("stopThread")</code> argument) is called in 878 * addition. 879 * Again, this may result in throwing a 880 * <code>SecurityException</code> (in the current thread). 881 * <p> 882 * The thread represented by this thread is forced to stop whatever 883 * it is doing abnormally and to throw a newly created 884 * <code>ThreadDeath</code> object as an exception. 885 * <p> 886 * It is permitted to stop a thread that has not yet been started. 887 * If the thread is eventually started, it immediately terminates. 888 * <p> 889 * An application should not normally try to catch 890 * <code>ThreadDeath</code> unless it must do some extraordinary 891 * cleanup operation (note that the throwing of 892 * <code>ThreadDeath</code> causes <code>finally</code> clauses of 893 * <code>try</code> statements to be executed before the thread 894 * officially dies). If a <code>catch</code> clause catches a 895 * <code>ThreadDeath</code> object, it is important to rethrow the 896 * object so that the thread actually dies. 897 * <p> 898 * The top-level error handler that reacts to otherwise uncaught 899 * exceptions does not print out a message or otherwise notify the 900 * application if the uncaught exception is an instance of 901 * <code>ThreadDeath</code>. 902 * 903 * @exception SecurityException if the current thread cannot 904 * modify this thread. 905 * @see #interrupt() 906 * @see #checkAccess() 907 * @see #run() 908 * @see #start() 909 * @see ThreadDeath 910 * @see ThreadGroup#uncaughtException(Thread,Throwable) 911 * @see SecurityManager#checkAccess(Thread) 912 * @see SecurityManager#checkPermission 913 * @deprecated This method is inherently unsafe. Stopping a thread with 914 * Thread.stop causes it to unlock all of the monitors that it 915 * has locked (as a natural consequence of the unchecked 916 * <code>ThreadDeath</code> exception propagating up the stack). If 917 * any of the objects previously protected by these monitors were in 918 * an inconsistent state, the damaged objects become visible to 919 * other threads, potentially resulting in arbitrary behavior. Many 920 * uses of <code>stop</code> should be replaced by code that simply 921 * modifies some variable to indicate that the target thread should 922 * stop running. The target thread should check this variable 923 * regularly, and return from its run method in an orderly fashion 924 * if the variable indicates that it is to stop running. If the 925 * target thread waits for long periods (on a condition variable, 926 * for example), the <code>interrupt</code> method should be used to 927 * interrupt the wait. 928 * For more information, see 929 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why 930 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. 931 */ 932 @Deprecated(since="1.2") 933 public final void stop() { 934 SecurityManager security = System.getSecurityManager(); 935 if (security != null) { 936 checkAccess(); 937 if (this != Thread.currentThread()) { 938 security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION); 939 } 940 } 941 // A zero status value corresponds to "NEW", it can't change to 942 // not-NEW because we hold the lock. 943 if (threadStatus != 0) { 944 resume(); // Wake up thread if it was suspended; no-op otherwise 945 } 946 947 // The VM can handle all thread states 948 stop0(new ThreadDeath()); 949 } 950 951 /** 952 * Throws {@code UnsupportedOperationException}. 953 * 954 * @param obj ignored 955 * 956 * @deprecated This method was originally designed to force a thread to stop 957 * and throw a given {@code Throwable} as an exception. It was 958 * inherently unsafe (see {@link #stop()} for details), and furthermore 959 * could be used to generate exceptions that the target thread was 960 * not prepared to handle. 961 * For more information, see 962 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why 963 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. 964 * This method is subject to removal in a future version of Java SE. 965 */ 966 @Deprecated(since="1.2", forRemoval=true) 967 public final synchronized void stop(Throwable obj) { 968 throw new UnsupportedOperationException(); 969 } 970 971 /** 972 * Interrupts this thread. 973 * 974 * <p> Unless the current thread is interrupting itself, which is 975 * always permitted, the {@link #checkAccess() checkAccess} method 976 * of this thread is invoked, which may cause a {@link 977 * SecurityException} to be thrown. 978 * 979 * <p> If this thread is blocked in an invocation of the {@link 980 * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link 981 * Object#wait(long, int) wait(long, int)} methods of the {@link Object} 982 * class, or of the {@link #join()}, {@link #join(long)}, {@link 983 * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)}, 984 * methods of this class, then its interrupt status will be cleared and it 985 * will receive an {@link InterruptedException}. 986 * 987 * <p> If this thread is blocked in an I/O operation upon an {@link 988 * java.nio.channels.InterruptibleChannel InterruptibleChannel} 989 * then the channel will be closed, the thread's interrupt 990 * status will be set, and the thread will receive a {@link 991 * java.nio.channels.ClosedByInterruptException}. 992 * 993 * <p> If this thread is blocked in a {@link java.nio.channels.Selector} 994 * then the thread's interrupt status will be set and it will return 995 * immediately from the selection operation, possibly with a non-zero 996 * value, just as if the selector's {@link 997 * java.nio.channels.Selector#wakeup wakeup} method were invoked. 998 * 999 * <p> If none of the previous conditions hold then this thread's interrupt 1000 * status will be set. </p> 1001 * 1002 * <p> Interrupting a thread that is not alive need not have any effect. 1003 * 1004 * @throws SecurityException 1005 * if the current thread cannot modify this thread 1006 * 1007 * @revised 6.0 1008 * @spec JSR-51 1009 */ 1010 public void interrupt() { 1011 if (this != Thread.currentThread()) 1012 checkAccess(); 1013 1014 synchronized (blockerLock) { 1015 Interruptible b = blocker; 1016 if (b != null) { 1017 interrupt0(); // Just to set the interrupt flag 1018 b.interrupt(this); 1019 return; 1020 } 1021 } 1022 interrupt0(); 1023 } 1024 1025 /** 1026 * Tests whether the current thread has been interrupted. The 1027 * <i>interrupted status</i> of the thread is cleared by this method. In 1028 * other words, if this method were to be called twice in succession, the 1029 * second call would return false (unless the current thread were 1030 * interrupted again, after the first call had cleared its interrupted 1031 * status and before the second call had examined it). 1032 * 1033 * <p>A thread interruption ignored because a thread was not alive 1034 * at the time of the interrupt will be reflected by this method 1035 * returning false. 1036 * 1037 * @return <code>true</code> if the current thread has been interrupted; 1038 * <code>false</code> otherwise. 1039 * @see #isInterrupted() 1040 * @revised 6.0 1041 */ 1042 public static boolean interrupted() { 1043 return currentThread().isInterrupted(true); 1044 } 1045 1046 /** 1047 * Tests whether this thread has been interrupted. The <i>interrupted 1048 * status</i> of the thread is unaffected by this method. 1049 * 1050 * <p>A thread interruption ignored because a thread was not alive 1051 * at the time of the interrupt will be reflected by this method 1052 * returning false. 1053 * 1054 * @return <code>true</code> if this thread has been interrupted; 1055 * <code>false</code> otherwise. 1056 * @see #interrupted() 1057 * @revised 6.0 1058 */ 1059 public boolean isInterrupted() { 1060 return isInterrupted(false); 1061 } 1062 1063 /** 1064 * Tests if some Thread has been interrupted. The interrupted state 1065 * is reset or not based on the value of ClearInterrupted that is 1066 * passed. 1067 */ 1068 @HotSpotIntrinsicCandidate 1069 private native boolean isInterrupted(boolean ClearInterrupted); 1070 1071 /** 1072 * Throws {@link NoSuchMethodError}. 1073 * 1074 * @deprecated This method was originally designed to destroy this 1075 * thread without any cleanup. Any monitors it held would have 1076 * remained locked. However, the method was never implemented. 1077 * If it were to be implemented, it would be deadlock-prone in 1078 * much the manner of {@link #suspend}. If the target thread held 1079 * a lock protecting a critical system resource when it was 1080 * destroyed, no thread could ever access this resource again. 1081 * If another thread ever attempted to lock this resource, deadlock 1082 * would result. Such deadlocks typically manifest themselves as 1083 * "frozen" processes. For more information, see 1084 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html"> 1085 * Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. 1086 * This method is subject to removal in a future version of Java SE. 1087 * @throws NoSuchMethodError always 1088 */ 1089 @Deprecated(since="1.5", forRemoval=true) 1090 public void destroy() { 1091 throw new NoSuchMethodError(); 1092 } 1093 1094 /** 1095 * Tests if this thread is alive. A thread is alive if it has 1096 * been started and has not yet died. 1097 * 1098 * @return <code>true</code> if this thread is alive; 1099 * <code>false</code> otherwise. 1100 */ 1101 public final native boolean isAlive(); 1102 1103 /** 1104 * Suspends this thread. 1105 * <p> 1106 * First, the <code>checkAccess</code> method of this thread is called 1107 * with no arguments. This may result in throwing a 1108 * <code>SecurityException </code>(in the current thread). 1109 * <p> 1110 * If the thread is alive, it is suspended and makes no further 1111 * progress unless and until it is resumed. 1112 * 1113 * @exception SecurityException if the current thread cannot modify 1114 * this thread. 1115 * @see #checkAccess 1116 * @deprecated This method has been deprecated, as it is 1117 * inherently deadlock-prone. If the target thread holds a lock on the 1118 * monitor protecting a critical system resource when it is suspended, no 1119 * thread can access this resource until the target thread is resumed. If 1120 * the thread that would resume the target thread attempts to lock this 1121 * monitor prior to calling <code>resume</code>, deadlock results. Such 1122 * deadlocks typically manifest themselves as "frozen" processes. 1123 * For more information, see 1124 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why 1125 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. 1126 */ 1127 @Deprecated(since="1.2") 1128 public final void suspend() { 1129 checkAccess(); 1130 suspend0(); 1131 } 1132 1133 /** 1134 * Resumes a suspended thread. 1135 * <p> 1136 * First, the <code>checkAccess</code> method of this thread is called 1137 * with no arguments. This may result in throwing a 1138 * <code>SecurityException</code> (in the current thread). 1139 * <p> 1140 * If the thread is alive but suspended, it is resumed and is 1141 * permitted to make progress in its execution. 1142 * 1143 * @exception SecurityException if the current thread cannot modify this 1144 * thread. 1145 * @see #checkAccess 1146 * @see #suspend() 1147 * @deprecated This method exists solely for use with {@link #suspend}, 1148 * which has been deprecated because it is deadlock-prone. 1149 * For more information, see 1150 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why 1151 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. 1152 */ 1153 @Deprecated(since="1.2") 1154 public final void resume() { 1155 checkAccess(); 1156 resume0(); 1157 } 1158 1159 /** 1160 * Changes the priority of this thread. 1161 * <p> 1162 * First the <code>checkAccess</code> method of this thread is called 1163 * with no arguments. This may result in throwing a 1164 * <code>SecurityException</code>. 1165 * <p> 1166 * Otherwise, the priority of this thread is set to the smaller of 1167 * the specified <code>newPriority</code> and the maximum permitted 1168 * priority of the thread's thread group. 1169 * 1170 * @param newPriority priority to set this thread to 1171 * @exception IllegalArgumentException If the priority is not in the 1172 * range <code>MIN_PRIORITY</code> to 1173 * <code>MAX_PRIORITY</code>. 1174 * @exception SecurityException if the current thread cannot modify 1175 * this thread. 1176 * @see #getPriority 1177 * @see #checkAccess() 1178 * @see #getThreadGroup() 1179 * @see #MAX_PRIORITY 1180 * @see #MIN_PRIORITY 1181 * @see ThreadGroup#getMaxPriority() 1182 */ 1183 public final void setPriority(int newPriority) { 1184 ThreadGroup g; 1185 checkAccess(); 1186 if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) { 1187 throw new IllegalArgumentException(); 1188 } 1189 if((g = getThreadGroup()) != null) { 1190 if (newPriority > g.getMaxPriority()) { 1191 newPriority = g.getMaxPriority(); 1192 } 1193 setPriority0(priority = newPriority); 1194 } 1195 } 1196 1197 /** 1198 * Returns this thread's priority. 1199 * 1200 * @return this thread's priority. 1201 * @see #setPriority 1202 */ 1203 public final int getPriority() { 1204 return priority; 1205 } 1206 1207 /** 1208 * Changes the name of this thread to be equal to the argument 1209 * <code>name</code>. 1210 * <p> 1211 * First the <code>checkAccess</code> method of this thread is called 1212 * with no arguments. This may result in throwing a 1213 * <code>SecurityException</code>. 1214 * 1215 * @param name the new name for this thread. 1216 * @exception SecurityException if the current thread cannot modify this 1217 * thread. 1218 * @see #getName 1219 * @see #checkAccess() 1220 */ 1221 public final synchronized void setName(String name) { 1222 checkAccess(); 1223 if (name == null) { 1224 throw new NullPointerException("name cannot be null"); 1225 } 1226 1227 this.name = name; 1228 if (threadStatus != 0) { 1229 setNativeName(name); 1230 } 1231 } 1232 1233 /** 1234 * Returns this thread's name. 1235 * 1236 * @return this thread's name. 1237 * @see #setName(String) 1238 */ 1239 public final String getName() { 1240 return name; 1241 } 1242 1243 /** 1244 * Returns the thread group to which this thread belongs. 1245 * This method returns null if this thread has died 1246 * (been stopped). 1247 * 1248 * @return this thread's thread group. 1249 */ 1250 public final ThreadGroup getThreadGroup() { 1251 return group; 1252 } 1253 1254 /** 1255 * Returns an estimate of the number of active threads in the current 1256 * thread's {@linkplain java.lang.ThreadGroup thread group} and its 1257 * subgroups. Recursively iterates over all subgroups in the current 1258 * thread's thread group. 1259 * 1260 * <p> The value returned is only an estimate because the number of 1261 * threads may change dynamically while this method traverses internal 1262 * data structures, and might be affected by the presence of certain 1263 * system threads. This method is intended primarily for debugging 1264 * and monitoring purposes. 1265 * 1266 * @return an estimate of the number of active threads in the current 1267 * thread's thread group and in any other thread group that 1268 * has the current thread's thread group as an ancestor 1269 */ 1270 public static int activeCount() { 1271 return currentThread().getThreadGroup().activeCount(); 1272 } 1273 1274 /** 1275 * Copies into the specified array every active thread in the current 1276 * thread's thread group and its subgroups. This method simply 1277 * invokes the {@link java.lang.ThreadGroup#enumerate(Thread[])} 1278 * method of the current thread's thread group. 1279 * 1280 * <p> An application might use the {@linkplain #activeCount activeCount} 1281 * method to get an estimate of how big the array should be, however 1282 * <i>if the array is too short to hold all the threads, the extra threads 1283 * are silently ignored.</i> If it is critical to obtain every active 1284 * thread in the current thread's thread group and its subgroups, the 1285 * invoker should verify that the returned int value is strictly less 1286 * than the length of {@code tarray}. 1287 * 1288 * <p> Due to the inherent race condition in this method, it is recommended 1289 * that the method only be used for debugging and monitoring purposes. 1290 * 1291 * @param tarray 1292 * an array into which to put the list of threads 1293 * 1294 * @return the number of threads put into the array 1295 * 1296 * @throws SecurityException 1297 * if {@link java.lang.ThreadGroup#checkAccess} determines that 1298 * the current thread cannot access its thread group 1299 */ 1300 public static int enumerate(Thread tarray[]) { 1301 return currentThread().getThreadGroup().enumerate(tarray); 1302 } 1303 1304 /** 1305 * Counts the number of stack frames in this thread. The thread must 1306 * be suspended. 1307 * 1308 * @return the number of stack frames in this thread. 1309 * @exception IllegalThreadStateException if this thread is not 1310 * suspended. 1311 * @deprecated The definition of this call depends on {@link #suspend}, 1312 * which is deprecated. Further, the results of this call 1313 * were never well-defined. 1314 * This method is subject to removal in a future version of Java SE. 1315 * @see StackWalker 1316 */ 1317 @Deprecated(since="1.2", forRemoval=true) 1318 public native int countStackFrames(); 1319 1320 /** 1321 * Waits at most {@code millis} milliseconds for this thread to 1322 * die. A timeout of {@code 0} means to wait forever. 1323 * 1324 * <p> This implementation uses a loop of {@code this.wait} calls 1325 * conditioned on {@code this.isAlive}. As a thread terminates the 1326 * {@code this.notifyAll} method is invoked. It is recommended that 1327 * applications not use {@code wait}, {@code notify}, or 1328 * {@code notifyAll} on {@code Thread} instances. 1329 * 1330 * @param millis 1331 * the time to wait in milliseconds 1332 * 1333 * @throws IllegalArgumentException 1334 * if the value of {@code millis} is negative 1335 * 1336 * @throws InterruptedException 1337 * if any thread has interrupted the current thread. The 1338 * <i>interrupted status</i> of the current thread is 1339 * cleared when this exception is thrown. 1340 */ 1341 public final synchronized void join(long millis) 1342 throws InterruptedException { 1343 long base = System.currentTimeMillis(); 1344 long now = 0; 1345 1346 if (millis < 0) { 1347 throw new IllegalArgumentException("timeout value is negative"); 1348 } 1349 1350 if (millis == 0) { 1351 while (isAlive()) { 1352 wait(0); 1353 } 1354 } else { 1355 while (isAlive()) { 1356 long delay = millis - now; 1357 if (delay <= 0) { 1358 break; 1359 } 1360 wait(delay); 1361 now = System.currentTimeMillis() - base; 1362 } 1363 } 1364 } 1365 1366 /** 1367 * Waits at most {@code millis} milliseconds plus 1368 * {@code nanos} nanoseconds for this thread to die. 1369 * 1370 * <p> This implementation uses a loop of {@code this.wait} calls 1371 * conditioned on {@code this.isAlive}. As a thread terminates the 1372 * {@code this.notifyAll} method is invoked. It is recommended that 1373 * applications not use {@code wait}, {@code notify}, or 1374 * {@code notifyAll} on {@code Thread} instances. 1375 * 1376 * @param millis 1377 * the time to wait in milliseconds 1378 * 1379 * @param nanos 1380 * {@code 0-999999} additional nanoseconds to wait 1381 * 1382 * @throws IllegalArgumentException 1383 * if the value of {@code millis} is negative, or the value 1384 * of {@code nanos} is not in the range {@code 0-999999} 1385 * 1386 * @throws InterruptedException 1387 * if any thread has interrupted the current thread. The 1388 * <i>interrupted status</i> of the current thread is 1389 * cleared when this exception is thrown. 1390 */ 1391 public final synchronized void join(long millis, int nanos) 1392 throws InterruptedException { 1393 1394 if (millis < 0) { 1395 throw new IllegalArgumentException("timeout value is negative"); 1396 } 1397 1398 if (nanos < 0 || nanos > 999999) { 1399 throw new IllegalArgumentException( 1400 "nanosecond timeout value out of range"); 1401 } 1402 1403 if (nanos >= 500000 || (nanos != 0 && millis == 0)) { 1404 millis++; 1405 } 1406 1407 join(millis); 1408 } 1409 1410 /** 1411 * Waits for this thread to die. 1412 * 1413 * <p> An invocation of this method behaves in exactly the same 1414 * way as the invocation 1415 * 1416 * <blockquote> 1417 * {@linkplain #join(long) join}{@code (0)} 1418 * </blockquote> 1419 * 1420 * @throws InterruptedException 1421 * if any thread has interrupted the current thread. The 1422 * <i>interrupted status</i> of the current thread is 1423 * cleared when this exception is thrown. 1424 */ 1425 public final void join() throws InterruptedException { 1426 join(0); 1427 } 1428 1429 /** 1430 * Prints a stack trace of the current thread to the standard error stream. 1431 * This method is used only for debugging. 1432 */ 1433 public static void dumpStack() { 1434 new Exception("Stack trace").printStackTrace(); 1435 } 1436 1437 /** 1438 * Marks this thread as either a {@linkplain #isDaemon daemon} thread 1439 * or a user thread. The Java Virtual Machine exits when the only 1440 * threads running are all daemon threads. 1441 * 1442 * <p> This method must be invoked before the thread is started. 1443 * 1444 * @param on 1445 * if {@code true}, marks this thread as a daemon thread 1446 * 1447 * @throws IllegalThreadStateException 1448 * if this thread is {@linkplain #isAlive alive} 1449 * 1450 * @throws SecurityException 1451 * if {@link #checkAccess} determines that the current 1452 * thread cannot modify this thread 1453 */ 1454 public final void setDaemon(boolean on) { 1455 checkAccess(); 1456 if (isAlive()) { 1457 throw new IllegalThreadStateException(); 1458 } 1459 daemon = on; 1460 } 1461 1462 /** 1463 * Tests if this thread is a daemon thread. 1464 * 1465 * @return <code>true</code> if this thread is a daemon thread; 1466 * <code>false</code> otherwise. 1467 * @see #setDaemon(boolean) 1468 */ 1469 public final boolean isDaemon() { 1470 return daemon; 1471 } 1472 1473 /** 1474 * Determines if the currently running thread has permission to 1475 * modify this thread. 1476 * <p> 1477 * If there is a security manager, its <code>checkAccess</code> method 1478 * is called with this thread as its argument. This may result in 1479 * throwing a <code>SecurityException</code>. 1480 * 1481 * @exception SecurityException if the current thread is not allowed to 1482 * access this thread. 1483 * @see SecurityManager#checkAccess(Thread) 1484 */ 1485 public final void checkAccess() { 1486 SecurityManager security = System.getSecurityManager(); 1487 if (security != null) { 1488 security.checkAccess(this); 1489 } 1490 } 1491 1492 /** 1493 * Returns a string representation of this thread, including the 1494 * thread's name, priority, and thread group. 1495 * 1496 * @return a string representation of this thread. 1497 */ 1498 public String toString() { 1499 ThreadGroup group = getThreadGroup(); 1500 if (group != null) { 1501 return "Thread[" + getName() + "," + getPriority() + "," + 1502 group.getName() + "]"; 1503 } else { 1504 return "Thread[" + getName() + "," + getPriority() + "," + 1505 "" + "]"; 1506 } 1507 } 1508 1509 /** 1510 * Returns the context ClassLoader for this Thread. The context 1511 * ClassLoader is provided by the creator of the thread for use 1512 * by code running in this thread when loading classes and resources. 1513 * If not {@linkplain #setContextClassLoader set}, the default is the 1514 * ClassLoader context of the parent Thread. The context ClassLoader of the 1515 * primordial thread is typically set to the class loader used to load the 1516 * application. 1517 * 1518 * <p>If a security manager is present, and the invoker's class loader is not 1519 * {@code null} and is not the same as or an ancestor of the context class 1520 * loader, then this method invokes the security manager's {@link 1521 * SecurityManager#checkPermission(java.security.Permission) checkPermission} 1522 * method with a {@link RuntimePermission RuntimePermission}{@code 1523 * ("getClassLoader")} permission to verify that retrieval of the context 1524 * class loader is permitted. 1525 * 1526 * @return the context ClassLoader for this Thread, or {@code null} 1527 * indicating the system class loader (or, failing that, the 1528 * bootstrap class loader) 1529 * 1530 * @throws SecurityException 1531 * if the current thread cannot get the context ClassLoader 1532 * 1533 * @since 1.2 1534 */ 1535 @CallerSensitive 1536 public ClassLoader getContextClassLoader() { 1537 if (contextClassLoader == null) 1538 return null; 1539 SecurityManager sm = System.getSecurityManager(); 1540 if (sm != null) { 1541 ClassLoader.checkClassLoaderPermission(contextClassLoader, 1542 Reflection.getCallerClass()); 1543 } 1544 return contextClassLoader; 1545 } 1546 1547 /** 1548 * Sets the context ClassLoader for this Thread. The context 1549 * ClassLoader can be set when a thread is created, and allows 1550 * the creator of the thread to provide the appropriate class loader, 1551 * through {@code getContextClassLoader}, to code running in the thread 1552 * when loading classes and resources. 1553 * 1554 * <p>If a security manager is present, its {@link 1555 * SecurityManager#checkPermission(java.security.Permission) checkPermission} 1556 * method is invoked with a {@link RuntimePermission RuntimePermission}{@code 1557 * ("setContextClassLoader")} permission to see if setting the context 1558 * ClassLoader is permitted. 1559 * 1560 * @param cl 1561 * the context ClassLoader for this Thread, or null indicating the 1562 * system class loader (or, failing that, the bootstrap class loader) 1563 * 1564 * @throws SecurityException 1565 * if the current thread cannot set the context ClassLoader 1566 * 1567 * @since 1.2 1568 */ 1569 public void setContextClassLoader(ClassLoader cl) { 1570 SecurityManager sm = System.getSecurityManager(); 1571 if (sm != null) { 1572 sm.checkPermission(new RuntimePermission("setContextClassLoader")); 1573 } 1574 contextClassLoader = cl; 1575 } 1576 1577 /** 1578 * Returns {@code true} if and only if the current thread holds the 1579 * monitor lock on the specified object. 1580 * 1581 * <p>This method is designed to allow a program to assert that 1582 * the current thread already holds a specified lock: 1583 * <pre> 1584 * assert Thread.holdsLock(obj); 1585 * </pre> 1586 * 1587 * @param obj the object on which to test lock ownership 1588 * @throws NullPointerException if obj is {@code null} 1589 * @return {@code true} if the current thread holds the monitor lock on 1590 * the specified object. 1591 * @since 1.4 1592 */ 1593 public static native boolean holdsLock(Object obj); 1594 1595 private static final StackTraceElement[] EMPTY_STACK_TRACE 1596 = new StackTraceElement[0]; 1597 1598 /** 1599 * Returns an array of stack trace elements representing the stack dump 1600 * of this thread. This method will return a zero-length array if 1601 * this thread has not started, has started but has not yet been 1602 * scheduled to run by the system, or has terminated. 1603 * If the returned array is of non-zero length then the first element of 1604 * the array represents the top of the stack, which is the most recent 1605 * method invocation in the sequence. The last element of the array 1606 * represents the bottom of the stack, which is the least recent method 1607 * invocation in the sequence. 1608 * 1609 * <p>If there is a security manager, and this thread is not 1610 * the current thread, then the security manager's 1611 * {@code checkPermission} method is called with a 1612 * {@code RuntimePermission("getStackTrace")} permission 1613 * to see if it's ok to get the stack trace. 1614 * 1615 * <p>Some virtual machines may, under some circumstances, omit one 1616 * or more stack frames from the stack trace. In the extreme case, 1617 * a virtual machine that has no stack trace information concerning 1618 * this thread is permitted to return a zero-length array from this 1619 * method. 1620 * 1621 * @return an array of {@code StackTraceElement}, 1622 * each represents one stack frame. 1623 * 1624 * @throws SecurityException 1625 * if a security manager exists and its 1626 * {@code checkPermission} method doesn't allow 1627 * getting the stack trace of thread. 1628 * @see SecurityManager#checkPermission 1629 * @see RuntimePermission 1630 * @see Throwable#getStackTrace 1631 * 1632 * @since 1.5 1633 */ 1634 public StackTraceElement[] getStackTrace() { 1635 if (this != Thread.currentThread()) { 1636 // check for getStackTrace permission 1637 SecurityManager security = System.getSecurityManager(); 1638 if (security != null) { 1639 security.checkPermission( 1640 SecurityConstants.GET_STACK_TRACE_PERMISSION); 1641 } 1642 // optimization so we do not call into the vm for threads that 1643 // have not yet started or have terminated 1644 if (!isAlive()) { 1645 return EMPTY_STACK_TRACE; 1646 } 1647 StackTraceElement[][] stackTraceArray = dumpThreads(new Thread[] {this}); 1648 StackTraceElement[] stackTrace = stackTraceArray[0]; 1649 // a thread that was alive during the previous isAlive call may have 1650 // since terminated, therefore not having a stacktrace. 1651 if (stackTrace == null) { 1652 stackTrace = EMPTY_STACK_TRACE; 1653 } 1654 return stackTrace; 1655 } else { 1656 return (new Exception()).getStackTrace(); 1657 } 1658 } 1659 1660 /** 1661 * Returns a map of stack traces for all live threads. 1662 * The map keys are threads and each map value is an array of 1663 * {@code StackTraceElement} that represents the stack dump 1664 * of the corresponding {@code Thread}. 1665 * The returned stack traces are in the format specified for 1666 * the {@link #getStackTrace getStackTrace} method. 1667 * 1668 * <p>The threads may be executing while this method is called. 1669 * The stack trace of each thread only represents a snapshot and 1670 * each stack trace may be obtained at different time. A zero-length 1671 * array will be returned in the map value if the virtual machine has 1672 * no stack trace information about a thread. 1673 * 1674 * <p>If there is a security manager, then the security manager's 1675 * {@code checkPermission} method is called with a 1676 * {@code RuntimePermission("getStackTrace")} permission as well as 1677 * {@code RuntimePermission("modifyThreadGroup")} permission 1678 * to see if it is ok to get the stack trace of all threads. 1679 * 1680 * @return a {@code Map} from {@code Thread} to an array of 1681 * {@code StackTraceElement} that represents the stack trace of 1682 * the corresponding thread. 1683 * 1684 * @throws SecurityException 1685 * if a security manager exists and its 1686 * {@code checkPermission} method doesn't allow 1687 * getting the stack trace of thread. 1688 * @see #getStackTrace 1689 * @see SecurityManager#checkPermission 1690 * @see RuntimePermission 1691 * @see Throwable#getStackTrace 1692 * 1693 * @since 1.5 1694 */ 1695 public static Map<Thread, StackTraceElement[]> getAllStackTraces() { 1696 // check for getStackTrace permission 1697 SecurityManager security = System.getSecurityManager(); 1698 if (security != null) { 1699 security.checkPermission( 1700 SecurityConstants.GET_STACK_TRACE_PERMISSION); 1701 security.checkPermission( 1702 SecurityConstants.MODIFY_THREADGROUP_PERMISSION); 1703 } 1704 1705 // Get a snapshot of the list of all threads 1706 Thread[] threads = getThreads(); 1707 StackTraceElement[][] traces = dumpThreads(threads); 1708 Map<Thread, StackTraceElement[]> m = new HashMap<>(threads.length); 1709 for (int i = 0; i < threads.length; i++) { 1710 StackTraceElement[] stackTrace = traces[i]; 1711 if (stackTrace != null) { 1712 m.put(threads[i], stackTrace); 1713 } 1714 // else terminated so we don't put it in the map 1715 } 1716 return m; 1717 } 1718 1719 1720 private static final RuntimePermission SUBCLASS_IMPLEMENTATION_PERMISSION = 1721 new RuntimePermission("enableContextClassLoaderOverride"); 1722 1723 /** cache of subclass security audit results */ 1724 /* Replace with ConcurrentReferenceHashMap when/if it appears in a future 1725 * release */ 1726 private static class Caches { 1727 /** cache of subclass security audit results */ 1728 static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits = 1729 new ConcurrentHashMap<>(); 1730 1731 /** queue for WeakReferences to audited subclasses */ 1732 static final ReferenceQueue<Class<?>> subclassAuditsQueue = 1733 new ReferenceQueue<>(); 1734 } 1735 1736 /** 1737 * Verifies that this (possibly subclass) instance can be constructed 1738 * without violating security constraints: the subclass must not override 1739 * security-sensitive non-final methods, or else the 1740 * "enableContextClassLoaderOverride" RuntimePermission is checked. 1741 */ 1742 private static boolean isCCLOverridden(Class<?> cl) { 1743 if (cl == Thread.class) 1744 return false; 1745 1746 processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits); 1747 WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue); 1748 Boolean result = Caches.subclassAudits.get(key); 1749 if (result == null) { 1750 result = Boolean.valueOf(auditSubclass(cl)); 1751 Caches.subclassAudits.putIfAbsent(key, result); 1752 } 1753 1754 return result.booleanValue(); 1755 } 1756 1757 /** 1758 * Performs reflective checks on given subclass to verify that it doesn't 1759 * override security-sensitive non-final methods. Returns true if the 1760 * subclass overrides any of the methods, false otherwise. 1761 */ 1762 private static boolean auditSubclass(final Class<?> subcl) { 1763 Boolean result = AccessController.doPrivileged( 1764 new PrivilegedAction<>() { 1765 public Boolean run() { 1766 for (Class<?> cl = subcl; 1767 cl != Thread.class; 1768 cl = cl.getSuperclass()) 1769 { 1770 try { 1771 cl.getDeclaredMethod("getContextClassLoader", new Class<?>[0]); 1772 return Boolean.TRUE; 1773 } catch (NoSuchMethodException ex) { 1774 } 1775 try { 1776 Class<?>[] params = {ClassLoader.class}; 1777 cl.getDeclaredMethod("setContextClassLoader", params); 1778 return Boolean.TRUE; 1779 } catch (NoSuchMethodException ex) { 1780 } 1781 } 1782 return Boolean.FALSE; 1783 } 1784 } 1785 ); 1786 return result.booleanValue(); 1787 } 1788 1789 private static native StackTraceElement[][] dumpThreads(Thread[] threads); 1790 private static native Thread[] getThreads(); 1791 1792 /** 1793 * Returns the identifier of this Thread. The thread ID is a positive 1794 * {@code long} number generated when this thread was created. 1795 * The thread ID is unique and remains unchanged during its lifetime. 1796 * When a thread is terminated, this thread ID may be reused. 1797 * 1798 * @return this thread's ID. 1799 * @since 1.5 1800 */ 1801 public long getId() { 1802 return tid; 1803 } 1804 1805 /** 1806 * A thread state. A thread can be in one of the following states: 1807 * <ul> 1808 * <li>{@link #NEW}<br> 1809 * A thread that has not yet started is in this state. 1810 * </li> 1811 * <li>{@link #RUNNABLE}<br> 1812 * A thread executing in the Java virtual machine is in this state. 1813 * </li> 1814 * <li>{@link #BLOCKED}<br> 1815 * A thread that is blocked waiting for a monitor lock 1816 * is in this state. 1817 * </li> 1818 * <li>{@link #WAITING}<br> 1819 * A thread that is waiting indefinitely for another thread to 1820 * perform a particular action is in this state. 1821 * </li> 1822 * <li>{@link #TIMED_WAITING}<br> 1823 * A thread that is waiting for another thread to perform an action 1824 * for up to a specified waiting time is in this state. 1825 * </li> 1826 * <li>{@link #TERMINATED}<br> 1827 * A thread that has exited is in this state. 1828 * </li> 1829 * </ul> 1830 * 1831 * <p> 1832 * A thread can be in only one state at a given point in time. 1833 * These states are virtual machine states which do not reflect 1834 * any operating system thread states. 1835 * 1836 * @since 1.5 1837 * @see #getState 1838 */ 1839 public enum State { 1840 /** 1841 * Thread state for a thread which has not yet started. 1842 */ 1843 NEW, 1844 1845 /** 1846 * Thread state for a runnable thread. A thread in the runnable 1847 * state is executing in the Java virtual machine but it may 1848 * be waiting for other resources from the operating system 1849 * such as processor. 1850 */ 1851 RUNNABLE, 1852 1853 /** 1854 * Thread state for a thread blocked waiting for a monitor lock. 1855 * A thread in the blocked state is waiting for a monitor lock 1856 * to enter a synchronized block/method or 1857 * reenter a synchronized block/method after calling 1858 * {@link Object#wait() Object.wait}. 1859 */ 1860 BLOCKED, 1861 1862 /** 1863 * Thread state for a waiting thread. 1864 * A thread is in the waiting state due to calling one of the 1865 * following methods: 1866 * <ul> 1867 * <li>{@link Object#wait() Object.wait} with no timeout</li> 1868 * <li>{@link #join() Thread.join} with no timeout</li> 1869 * <li>{@link LockSupport#park() LockSupport.park}</li> 1870 * </ul> 1871 * 1872 * <p>A thread in the waiting state is waiting for another thread to 1873 * perform a particular action. 1874 * 1875 * For example, a thread that has called {@code Object.wait()} 1876 * on an object is waiting for another thread to call 1877 * {@code Object.notify()} or {@code Object.notifyAll()} on 1878 * that object. A thread that has called {@code Thread.join()} 1879 * is waiting for a specified thread to terminate. 1880 */ 1881 WAITING, 1882 1883 /** 1884 * Thread state for a waiting thread with a specified waiting time. 1885 * A thread is in the timed waiting state due to calling one of 1886 * the following methods with a specified positive waiting time: 1887 * <ul> 1888 * <li>{@link #sleep Thread.sleep}</li> 1889 * <li>{@link Object#wait(long) Object.wait} with timeout</li> 1890 * <li>{@link #join(long) Thread.join} with timeout</li> 1891 * <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li> 1892 * <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li> 1893 * </ul> 1894 */ 1895 TIMED_WAITING, 1896 1897 /** 1898 * Thread state for a terminated thread. 1899 * The thread has completed execution. 1900 */ 1901 TERMINATED; 1902 } 1903 1904 /** 1905 * Returns the state of this thread. 1906 * This method is designed for use in monitoring of the system state, 1907 * not for synchronization control. 1908 * 1909 * @return this thread's state. 1910 * @since 1.5 1911 */ 1912 public State getState() { 1913 // get current thread state 1914 return jdk.internal.misc.VM.toThreadState(threadStatus); 1915 } 1916 1917 // Added in JSR-166 1918 1919 /** 1920 * Interface for handlers invoked when a {@code Thread} abruptly 1921 * terminates due to an uncaught exception. 1922 * <p>When a thread is about to terminate due to an uncaught exception 1923 * the Java Virtual Machine will query the thread for its 1924 * {@code UncaughtExceptionHandler} using 1925 * {@link #getUncaughtExceptionHandler} and will invoke the handler's 1926 * {@code uncaughtException} method, passing the thread and the 1927 * exception as arguments. 1928 * If a thread has not had its {@code UncaughtExceptionHandler} 1929 * explicitly set, then its {@code ThreadGroup} object acts as its 1930 * {@code UncaughtExceptionHandler}. If the {@code ThreadGroup} object 1931 * has no 1932 * special requirements for dealing with the exception, it can forward 1933 * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler 1934 * default uncaught exception handler}. 1935 * 1936 * @see #setDefaultUncaughtExceptionHandler 1937 * @see #setUncaughtExceptionHandler 1938 * @see ThreadGroup#uncaughtException 1939 * @since 1.5 1940 */ 1941 @FunctionalInterface 1942 public interface UncaughtExceptionHandler { 1943 /** 1944 * Method invoked when the given thread terminates due to the 1945 * given uncaught exception. 1946 * <p>Any exception thrown by this method will be ignored by the 1947 * Java Virtual Machine. 1948 * @param t the thread 1949 * @param e the exception 1950 */ 1951 void uncaughtException(Thread t, Throwable e); 1952 } 1953 1954 // null unless explicitly set 1955 private volatile UncaughtExceptionHandler uncaughtExceptionHandler; 1956 1957 // null unless explicitly set 1958 private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler; 1959 1960 /** 1961 * Set the default handler invoked when a thread abruptly terminates 1962 * due to an uncaught exception, and no other handler has been defined 1963 * for that thread. 1964 * 1965 * <p>Uncaught exception handling is controlled first by the thread, then 1966 * by the thread's {@link ThreadGroup} object and finally by the default 1967 * uncaught exception handler. If the thread does not have an explicit 1968 * uncaught exception handler set, and the thread's thread group 1969 * (including parent thread groups) does not specialize its 1970 * {@code uncaughtException} method, then the default handler's 1971 * {@code uncaughtException} method will be invoked. 1972 * <p>By setting the default uncaught exception handler, an application 1973 * can change the way in which uncaught exceptions are handled (such as 1974 * logging to a specific device, or file) for those threads that would 1975 * already accept whatever "default" behavior the system 1976 * provided. 1977 * 1978 * <p>Note that the default uncaught exception handler should not usually 1979 * defer to the thread's {@code ThreadGroup} object, as that could cause 1980 * infinite recursion. 1981 * 1982 * @param eh the object to use as the default uncaught exception handler. 1983 * If {@code null} then there is no default handler. 1984 * 1985 * @throws SecurityException if a security manager is present and it denies 1986 * {@link RuntimePermission}{@code ("setDefaultUncaughtExceptionHandler")} 1987 * 1988 * @see #setUncaughtExceptionHandler 1989 * @see #getUncaughtExceptionHandler 1990 * @see ThreadGroup#uncaughtException 1991 * @since 1.5 1992 */ 1993 public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler eh) { 1994 SecurityManager sm = System.getSecurityManager(); 1995 if (sm != null) { 1996 sm.checkPermission( 1997 new RuntimePermission("setDefaultUncaughtExceptionHandler") 1998 ); 1999 } 2000 2001 defaultUncaughtExceptionHandler = eh; 2002 } 2003 2004 /** 2005 * Returns the default handler invoked when a thread abruptly terminates 2006 * due to an uncaught exception. If the returned value is {@code null}, 2007 * there is no default. 2008 * @since 1.5 2009 * @see #setDefaultUncaughtExceptionHandler 2010 * @return the default uncaught exception handler for all threads 2011 */ 2012 public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler(){ 2013 return defaultUncaughtExceptionHandler; 2014 } 2015 2016 /** 2017 * Returns the handler invoked when this thread abruptly terminates 2018 * due to an uncaught exception. If this thread has not had an 2019 * uncaught exception handler explicitly set then this thread's 2020 * {@code ThreadGroup} object is returned, unless this thread 2021 * has terminated, in which case {@code null} is returned. 2022 * @since 1.5 2023 * @return the uncaught exception handler for this thread 2024 */ 2025 public UncaughtExceptionHandler getUncaughtExceptionHandler() { 2026 return uncaughtExceptionHandler != null ? 2027 uncaughtExceptionHandler : group; 2028 } 2029 2030 /** 2031 * Set the handler invoked when this thread abruptly terminates 2032 * due to an uncaught exception. 2033 * <p>A thread can take full control of how it responds to uncaught 2034 * exceptions by having its uncaught exception handler explicitly set. 2035 * If no such handler is set then the thread's {@code ThreadGroup} 2036 * object acts as its handler. 2037 * @param eh the object to use as this thread's uncaught exception 2038 * handler. If {@code null} then this thread has no explicit handler. 2039 * @throws SecurityException if the current thread is not allowed to 2040 * modify this thread. 2041 * @see #setDefaultUncaughtExceptionHandler 2042 * @see ThreadGroup#uncaughtException 2043 * @since 1.5 2044 */ 2045 public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh) { 2046 checkAccess(); 2047 uncaughtExceptionHandler = eh; 2048 } 2049 2050 /** 2051 * Dispatch an uncaught exception to the handler. This method is 2052 * intended to be called only by the JVM. 2053 */ 2054 private void dispatchUncaughtException(Throwable e) { 2055 getUncaughtExceptionHandler().uncaughtException(this, e); 2056 } 2057 2058 /** 2059 * Removes from the specified map any keys that have been enqueued 2060 * on the specified reference queue. 2061 */ 2062 static void processQueue(ReferenceQueue<Class<?>> queue, 2063 ConcurrentMap<? extends 2064 WeakReference<Class<?>>, ?> map) 2065 { 2066 Reference<? extends Class<?>> ref; 2067 while((ref = queue.poll()) != null) { 2068 map.remove(ref); 2069 } 2070 } 2071 2072 /** 2073 * Weak key for Class objects. 2074 **/ 2075 static class WeakClassKey extends WeakReference<Class<?>> { 2076 /** 2077 * saved value of the referent's identity hash code, to maintain 2078 * a consistent hash code after the referent has been cleared 2079 */ 2080 private final int hash; 2081 2082 /** 2083 * Create a new WeakClassKey to the given object, registered 2084 * with a queue. 2085 */ 2086 WeakClassKey(Class<?> cl, ReferenceQueue<Class<?>> refQueue) { 2087 super(cl, refQueue); 2088 hash = System.identityHashCode(cl); 2089 } 2090 2091 /** 2092 * Returns the identity hash code of the original referent. 2093 */ 2094 @Override 2095 public int hashCode() { 2096 return hash; 2097 } 2098 2099 /** 2100 * Returns true if the given object is this identical 2101 * WeakClassKey instance, or, if this object's referent has not 2102 * been cleared, if the given object is another WeakClassKey 2103 * instance with the identical non-null referent as this one. 2104 */ 2105 @Override 2106 public boolean equals(Object obj) { 2107 if (obj == this) 2108 return true; 2109 2110 if (obj instanceof WeakClassKey) { 2111 Object referent = get(); 2112 return (referent != null) && 2113 (referent == ((WeakClassKey) obj).get()); 2114 } else { 2115 return false; 2116 } 2117 } 2118 } 2119 2120 2121 // The following three initially uninitialized fields are exclusively 2122 // managed by class java.util.concurrent.ThreadLocalRandom. These 2123 // fields are used to build the high-performance PRNGs in the 2124 // concurrent code, and we can not risk accidental false sharing. 2125 // Hence, the fields are isolated with @Contended. 2126 2127 /** The current seed for a ThreadLocalRandom */ 2128 @jdk.internal.vm.annotation.Contended("tlr") 2129 long threadLocalRandomSeed; 2130 2131 /** Probe hash value; nonzero if threadLocalRandomSeed initialized */ 2132 @jdk.internal.vm.annotation.Contended("tlr") 2133 int threadLocalRandomProbe; 2134 2135 /** Secondary seed isolated from public ThreadLocalRandom sequence */ 2136 @jdk.internal.vm.annotation.Contended("tlr") 2137 int threadLocalRandomSecondarySeed; 2138 2139 /* Some private helper methods */ 2140 private native void setPriority0(int newPriority); 2141 private native void stop0(Object o); 2142 private native void suspend0(); 2143 private native void resume0(); 2144 private native void interrupt0(); 2145 private native void setNativeName(String name); 2146 }