0001 /*
0002 * Copyright 1994-2007 Sun Microsystems, Inc. All Rights Reserved.
0003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
0004 *
0005 * This code is free software; you can redistribute it and/or modify it
0006 * under the terms of the GNU General Public License version 2 only, as
0007 * published by the Free Software Foundation. Sun designates this
0008 * particular file as subject to the "Classpath" exception as provided
0009 * by Sun in the LICENSE file that accompanied this code.
0010 *
0011 * This code is distributed in the hope that it will be useful, but WITHOUT
0012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
0013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
0014 * version 2 for more details (a copy is included in the LICENSE file that
0015 * accompanied this code).
0016 *
0017 * You should have received a copy of the GNU General Public License version
0018 * 2 along with this work; if not, write to the Free Software Foundation,
0019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
0020 *
0021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
0022 * CA 95054 USA or visit www.sun.com if you need additional information or
0023 * have any questions.
0024 */
0025
0026 package java.lang;
0027
0028 import java.security.AccessController;
0029 import java.security.AccessControlContext;
0030 import java.security.PrivilegedAction;
0031 import java.util.Map;
0032 import java.util.HashMap;
0033 import java.util.Collections;
0034 import java.util.concurrent.locks.LockSupport;
0035 import sun.misc.SoftCache;
0036 import sun.nio.ch.Interruptible;
0037 import sun.security.util.SecurityConstants;
0038
0039 /**
0040 * A <i>thread</i> is a thread of execution in a program. The Java
0041 * Virtual Machine allows an application to have multiple threads of
0042 * execution running concurrently.
0043 * <p>
0044 * Every thread has a priority. Threads with higher priority are
0045 * executed in preference to threads with lower priority. Each thread
0046 * may or may not also be marked as a daemon. When code running in
0047 * some thread creates a new <code>Thread</code> object, the new
0048 * thread has its priority initially set equal to the priority of the
0049 * creating thread, and is a daemon thread if and only if the
0050 * creating thread is a daemon.
0051 * <p>
0052 * When a Java Virtual Machine starts up, there is usually a single
0053 * non-daemon thread (which typically calls the method named
0054 * <code>main</code> of some designated class). The Java Virtual
0055 * Machine continues to execute threads until either of the following
0056 * occurs:
0057 * <ul>
0058 * <li>The <code>exit</code> method of class <code>Runtime</code> has been
0059 * called and the security manager has permitted the exit operation
0060 * to take place.
0061 * <li>All threads that are not daemon threads have died, either by
0062 * returning from the call to the <code>run</code> method or by
0063 * throwing an exception that propagates beyond the <code>run</code>
0064 * method.
0065 * </ul>
0066 * <p>
0067 * There are two ways to create a new thread of execution. One is to
0068 * declare a class to be a subclass of <code>Thread</code>. This
0069 * subclass should override the <code>run</code> method of class
0070 * <code>Thread</code>. An instance of the subclass can then be
0071 * allocated and started. For example, a thread that computes primes
0072 * larger than a stated value could be written as follows:
0073 * <p><hr><blockquote><pre>
0074 * class PrimeThread extends Thread {
0075 * long minPrime;
0076 * PrimeThread(long minPrime) {
0077 * this.minPrime = minPrime;
0078 * }
0079 *
0080 * public void run() {
0081 * // compute primes larger than minPrime
0082 * . . .
0083 * }
0084 * }
0085 * </pre></blockquote><hr>
0086 * <p>
0087 * The following code would then create a thread and start it running:
0088 * <p><blockquote><pre>
0089 * PrimeThread p = new PrimeThread(143);
0090 * p.start();
0091 * </pre></blockquote>
0092 * <p>
0093 * The other way to create a thread is to declare a class that
0094 * implements the <code>Runnable</code> interface. That class then
0095 * implements the <code>run</code> method. An instance of the class can
0096 * then be allocated, passed as an argument when creating
0097 * <code>Thread</code>, and started. The same example in this other
0098 * style looks like the following:
0099 * <p><hr><blockquote><pre>
0100 * class PrimeRun implements Runnable {
0101 * long minPrime;
0102 * PrimeRun(long minPrime) {
0103 * this.minPrime = minPrime;
0104 * }
0105 *
0106 * public void run() {
0107 * // compute primes larger than minPrime
0108 * . . .
0109 * }
0110 * }
0111 * </pre></blockquote><hr>
0112 * <p>
0113 * The following code would then create a thread and start it running:
0114 * <p><blockquote><pre>
0115 * PrimeRun p = new PrimeRun(143);
0116 * new Thread(p).start();
0117 * </pre></blockquote>
0118 * <p>
0119 * Every thread has a name for identification purposes. More than
0120 * one thread may have the same name. If a name is not specified when
0121 * a thread is created, a new name is generated for it.
0122 *
0123 * @author unascribed
0124 * @version 1.184, 07/30/07
0125 * @see Runnable
0126 * @see Runtime#exit(int)
0127 * @see #run()
0128 * @see #stop()
0129 * @since JDK1.0
0130 */
0131 public class Thread implements Runnable {
0132 /* Make sure registerNatives is the first thing <clinit> does. */
0133 private static native void registerNatives();
0134
0135 static {
0136 registerNatives();
0137 }
0138
0139 private char name[];
0140 private int priority;
0141 private Thread threadQ;
0142 private long eetop;
0143
0144 /* Whether or not to single_step this thread. */
0145 private boolean single_step;
0146
0147 /* Whether or not the thread is a daemon thread. */
0148 private boolean daemon = false;
0149
0150 /* JVM state */
0151 private boolean stillborn = false;
0152
0153 /* What will be run. */
0154 private Runnable target;
0155
0156 /* The group of this thread */
0157 private ThreadGroup group;
0158
0159 /* The context ClassLoader for this thread */
0160 private ClassLoader contextClassLoader;
0161
0162 /* The inherited AccessControlContext of this thread */
0163 private AccessControlContext inheritedAccessControlContext;
0164
0165 /* For autonumbering anonymous threads. */
0166 private static int threadInitNumber;
0167
0168 private static synchronized int nextThreadNum() {
0169 return threadInitNumber++;
0170 }
0171
0172 /* ThreadLocal values pertaining to this thread. This map is maintained
0173 * by the ThreadLocal class. */
0174 ThreadLocal.ThreadLocalMap threadLocals = null;
0175
0176 /*
0177 * InheritableThreadLocal values pertaining to this thread. This map is
0178 * maintained by the InheritableThreadLocal class.
0179 */
0180 ThreadLocal.ThreadLocalMap inheritableThreadLocals = null;
0181
0182 /*
0183 * The requested stack size for this thread, or 0 if the creator did
0184 * not specify a stack size. It is up to the VM to do whatever it
0185 * likes with this number; some VMs will ignore it.
0186 */
0187 private long stackSize;
0188
0189 /*
0190 * JVM-private state that persists after native thread termination.
0191 */
0192 private long nativeParkEventPointer;
0193
0194 /*
0195 * Thread ID
0196 */
0197 private long tid;
0198
0199 /* For generating thread ID */
0200 private static long threadSeqNumber;
0201
0202 /* Java thread status for tools,
0203 * initialized to indicate thread 'not yet started'
0204 */
0205
0206 private int threadStatus = 0;
0207
0208 private static synchronized long nextThreadID() {
0209 return ++threadSeqNumber;
0210 }
0211
0212 /**
0213 * The argument supplied to the current call to
0214 * java.util.concurrent.locks.LockSupport.park.
0215 * Set by (private) java.util.concurrent.locks.LockSupport.setBlocker
0216 * Accessed using java.util.concurrent.locks.LockSupport.getBlocker
0217 */
0218 volatile Object parkBlocker;
0219
0220 /* The object in which this thread is blocked in an interruptible I/O
0221 * operation, if any. The blocker's interrupt method should be invoked
0222 * after setting this thread's interrupt status.
0223 */
0224 private volatile Interruptible blocker;
0225 private Object blockerLock = new Object();
0226
0227 /* Set the blocker field; invoked via sun.misc.SharedSecrets from java.nio code
0228 */
0229 void blockedOn(Interruptible b) {
0230 synchronized (blockerLock) {
0231 blocker = b;
0232 }
0233 }
0234
0235 /**
0236 * The minimum priority that a thread can have.
0237 */
0238 public final static int MIN_PRIORITY = 1;
0239
0240 /**
0241 * The default priority that is assigned to a thread.
0242 */
0243 public final static int NORM_PRIORITY = 5;
0244
0245 /**
0246 * The maximum priority that a thread can have.
0247 */
0248 public final static int MAX_PRIORITY = 10;
0249
0250 /* If stop was called before start */
0251 private boolean stopBeforeStart;
0252
0253 /* Remembered Throwable from stop before start */
0254 private Throwable throwableFromStop;
0255
0256 /**
0257 * Returns a reference to the currently executing thread object.
0258 *
0259 * @return the currently executing thread.
0260 */
0261 public static native Thread currentThread();
0262
0263 /**
0264 * Causes the currently executing thread object to temporarily pause
0265 * and allow other threads to execute.
0266 */
0267 public static native void yield();
0268
0269 /**
0270 * Causes the currently executing thread to sleep (temporarily cease
0271 * execution) for the specified number of milliseconds, subject to
0272 * the precision and accuracy of system timers and schedulers. The thread
0273 * does not lose ownership of any monitors.
0274 *
0275 * @param millis
0276 * the length of time to sleep in milliseconds
0277 *
0278 * @throws IllegalArgumentException
0279 * if the value of {@code millis} is negative
0280 *
0281 * @throws InterruptedException
0282 * if any thread has interrupted the current thread. The
0283 * <i>interrupted status</i> of the current thread is
0284 * cleared when this exception is thrown.
0285 */
0286 public static native void sleep(long millis)
0287 throws InterruptedException;
0288
0289 /**
0290 * Causes the currently executing thread to sleep (temporarily cease
0291 * execution) for the specified number of milliseconds plus the specified
0292 * number of nanoseconds, subject to the precision and accuracy of system
0293 * timers and schedulers. The thread does not lose ownership of any
0294 * monitors.
0295 *
0296 * @param millis
0297 * the length of time to sleep in milliseconds
0298 *
0299 * @param nanos
0300 * {@code 0-999999} additional nanoseconds to sleep
0301 *
0302 * @throws IllegalArgumentException
0303 * if the value of {@code millis} is negative, or the value of
0304 * {@code nanos} is not in the range {@code 0-999999}
0305 *
0306 * @throws InterruptedException
0307 * if any thread has interrupted the current thread. The
0308 * <i>interrupted status</i> of the current thread is
0309 * cleared when this exception is thrown.
0310 */
0311 public static void sleep(long millis, int nanos)
0312 throws InterruptedException {
0313 if (millis < 0) {
0314 throw new IllegalArgumentException(
0315 "timeout value is negative");
0316 }
0317
0318 if (nanos < 0 || nanos > 999999) {
0319 throw new IllegalArgumentException(
0320 "nanosecond timeout value out of range");
0321 }
0322
0323 if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
0324 millis++;
0325 }
0326
0327 sleep(millis);
0328 }
0329
0330 /**
0331 * Initializes a Thread.
0332 *
0333 * @param g the Thread group
0334 * @param target the object whose run() method gets called
0335 * @param name the name of the new Thread
0336 * @param stackSize the desired stack size for the new thread, or
0337 * zero to indicate that this parameter is to be ignored.
0338 */
0339 private void init(ThreadGroup g, Runnable target, String name,
0340 long stackSize) {
0341 Thread parent = currentThread();
0342 SecurityManager security = System.getSecurityManager();
0343 if (g == null) {
0344 /* Determine if it's an applet or not */
0345
0346 /* If there is a security manager, ask the security manager
0347 what to do. */
0348 if (security != null) {
0349 g = security.getThreadGroup();
0350 }
0351
0352 /* If the security doesn't have a strong opinion of the matter
0353 use the parent thread group. */
0354 if (g == null) {
0355 g = parent.getThreadGroup();
0356 }
0357 }
0358
0359 /* checkAccess regardless of whether or not threadgroup is
0360 explicitly passed in. */
0361 g.checkAccess();
0362
0363 /*
0364 * Do we have the required permissions?
0365 */
0366 if (security != null) {
0367 if (isCCLOverridden(getClass())) {
0368 security
0369 .checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
0370 }
0371 }
0372
0373 g.addUnstarted();
0374
0375 this .group = g;
0376 this .daemon = parent.isDaemon();
0377 this .priority = parent.getPriority();
0378 this .name = name.toCharArray();
0379 if (security == null || isCCLOverridden(parent.getClass()))
0380 this .contextClassLoader = parent.getContextClassLoader();
0381 else
0382 this .contextClassLoader = parent.contextClassLoader;
0383 this .inheritedAccessControlContext = AccessController
0384 .getContext();
0385 this .target = target;
0386 setPriority(priority);
0387 if (parent.inheritableThreadLocals != null)
0388 this .inheritableThreadLocals = ThreadLocal
0389 .createInheritedMap(parent.inheritableThreadLocals);
0390 /* Stash the specified stack size in case the VM cares */
0391 this .stackSize = stackSize;
0392
0393 /* Set thread ID */
0394 tid = nextThreadID();
0395 }
0396
0397 /**
0398 * Allocates a new <code>Thread</code> object. This constructor has
0399 * the same effect as <code>Thread(null, null,</code>
0400 * <i>gname</i><code>)</code>, where <b><i>gname</i></b> is
0401 * a newly generated name. Automatically generated names are of the
0402 * form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer.
0403 *
0404 * @see #Thread(ThreadGroup, Runnable, String)
0405 */
0406 public Thread() {
0407 init(null, null, "Thread-" + nextThreadNum(), 0);
0408 }
0409
0410 /**
0411 * Allocates a new <code>Thread</code> object. This constructor has
0412 * the same effect as <code>Thread(null, target,</code>
0413 * <i>gname</i><code>)</code>, where <i>gname</i> is
0414 * a newly generated name. Automatically generated names are of the
0415 * form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer.
0416 *
0417 * @param target the object whose <code>run</code> method is called.
0418 * @see #Thread(ThreadGroup, Runnable, String)
0419 */
0420 public Thread(Runnable target) {
0421 init(null, target, "Thread-" + nextThreadNum(), 0);
0422 }
0423
0424 /**
0425 * Allocates a new <code>Thread</code> object. This constructor has
0426 * the same effect as <code>Thread(group, target,</code>
0427 * <i>gname</i><code>)</code>, where <i>gname</i> is
0428 * a newly generated name. Automatically generated names are of the
0429 * form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer.
0430 *
0431 * @param group the thread group.
0432 * @param target the object whose <code>run</code> method is called.
0433 * @exception SecurityException if the current thread cannot create a
0434 * thread in the specified thread group.
0435 * @see #Thread(ThreadGroup, Runnable, String)
0436 */
0437 public Thread(ThreadGroup group, Runnable target) {
0438 init(group, target, "Thread-" + nextThreadNum(), 0);
0439 }
0440
0441 /**
0442 * Allocates a new <code>Thread</code> object. This constructor has
0443 * the same effect as <code>Thread(null, null, name)</code>.
0444 *
0445 * @param name the name of the new thread.
0446 * @see #Thread(ThreadGroup, Runnable, String)
0447 */
0448 public Thread(String name) {
0449 init(null, null, name, 0);
0450 }
0451
0452 /**
0453 * Allocates a new <code>Thread</code> object. This constructor has
0454 * the same effect as <code>Thread(group, null, name)</code>
0455 *
0456 * @param group the thread group.
0457 * @param name the name of the new thread.
0458 * @exception SecurityException if the current thread cannot create a
0459 * thread in the specified thread group.
0460 * @see #Thread(ThreadGroup, Runnable, String)
0461 */
0462 public Thread(ThreadGroup group, String name) {
0463 init(group, null, name, 0);
0464 }
0465
0466 /**
0467 * Allocates a new <code>Thread</code> object. This constructor has
0468 * the same effect as <code>Thread(null, target, name)</code>.
0469 *
0470 * @param target the object whose <code>run</code> method is called.
0471 * @param name the name of the new thread.
0472 * @see #Thread(ThreadGroup, Runnable, String)
0473 */
0474 public Thread(Runnable target, String name) {
0475 init(null, target, name, 0);
0476 }
0477
0478 /**
0479 * Allocates a new <code>Thread</code> object so that it has
0480 * <code>target</code> as its run object, has the specified
0481 * <code>name</code> as its name, and belongs to the thread group
0482 * referred to by <code>group</code>.
0483 * <p>
0484 * If <code>group</code> is <code>null</code> and there is a
0485 * security manager, the group is determined by the security manager's
0486 * <code>getThreadGroup</code> method. If <code>group</code> is
0487 * <code>null</code> and there is not a security manager, or the
0488 * security manager's <code>getThreadGroup</code> method returns
0489 * <code>null</code>, the group is set to be the same ThreadGroup
0490 * as the thread that is creating the new thread.
0491 *
0492 * <p>If there is a security manager, its <code>checkAccess</code>
0493 * method is called with the ThreadGroup as its argument.
0494 * <p>In addition, its <code>checkPermission</code>
0495 * method is called with the
0496 * <code>RuntimePermission("enableContextClassLoaderOverride")</code>
0497 * permission when invoked directly or indirectly by the constructor
0498 * of a subclass which overrides the <code>getContextClassLoader</code>
0499 * or <code>setContextClassLoader</code> methods.
0500 * This may result in a SecurityException.
0501
0502 * <p>
0503 * If the <code>target</code> argument is not <code>null</code>, the
0504 * <code>run</code> method of the <code>target</code> is called when
0505 * this thread is started. If the target argument is
0506 * <code>null</code>, this thread's <code>run</code> method is called
0507 * when this thread is started.
0508 * <p>
0509 * The priority of the newly created thread is set equal to the
0510 * priority of the thread creating it, that is, the currently running
0511 * thread. The method <code>setPriority</code> may be used to
0512 * change the priority to a new value.
0513 * <p>
0514 * The newly created thread is initially marked as being a daemon
0515 * thread if and only if the thread creating it is currently marked
0516 * as a daemon thread. The method <code>setDaemon </code> may be used
0517 * to change whether or not a thread is a daemon.
0518 *
0519 * @param group the thread group.
0520 * @param target the object whose <code>run</code> method is called.
0521 * @param name the name of the new thread.
0522 * @exception SecurityException if the current thread cannot create a
0523 * thread in the specified thread group or cannot
0524 * override the context class loader methods.
0525 * @see Runnable#run()
0526 * @see #run()
0527 * @see #setDaemon(boolean)
0528 * @see #setPriority(int)
0529 * @see ThreadGroup#checkAccess()
0530 * @see SecurityManager#checkAccess
0531 */
0532 public Thread(ThreadGroup group, Runnable target, String name) {
0533 init(group, target, name, 0);
0534 }
0535
0536 /**
0537 * Allocates a new <code>Thread</code> object so that it has
0538 * <code>target</code> as its run object, has the specified
0539 * <code>name</code> as its name, belongs to the thread group referred to
0540 * by <code>group</code>, and has the specified <i>stack size</i>.
0541 *
0542 * <p>This constructor is identical to {@link
0543 * #Thread(ThreadGroup,Runnable,String)} with the exception of the fact
0544 * that it allows the thread stack size to be specified. The stack size
0545 * is the approximate number of bytes of address space that the virtual
0546 * machine is to allocate for this thread's stack. <b>The effect of the
0547 * <tt>stackSize</tt> parameter, if any, is highly platform dependent.</b>
0548 *
0549 * <p>On some platforms, specifying a higher value for the
0550 * <tt>stackSize</tt> parameter may allow a thread to achieve greater
0551 * recursion depth before throwing a {@link StackOverflowError}.
0552 * Similarly, specifying a lower value may allow a greater number of
0553 * threads to exist concurrently without throwing an {@link
0554 * OutOfMemoryError} (or other internal error). The details of
0555 * the relationship between the value of the <tt>stackSize</tt> parameter
0556 * and the maximum recursion depth and concurrency level are
0557 * platform-dependent. <b>On some platforms, the value of the
0558 * <tt>stackSize</tt> parameter may have no effect whatsoever.</b>
0559 *
0560 * <p>The virtual machine is free to treat the <tt>stackSize</tt>
0561 * parameter as a suggestion. If the specified value is unreasonably low
0562 * for the platform, the virtual machine may instead use some
0563 * platform-specific minimum value; if the specified value is unreasonably
0564 * high, the virtual machine may instead use some platform-specific
0565 * maximum. Likewise, the virtual machine is free to round the specified
0566 * value up or down as it sees fit (or to ignore it completely).
0567 *
0568 * <p>Specifying a value of zero for the <tt>stackSize</tt> parameter will
0569 * cause this constructor to behave exactly like the
0570 * <tt>Thread(ThreadGroup, Runnable, String)</tt> constructor.
0571 *
0572 * <p><i>Due to the platform-dependent nature of the behavior of this
0573 * constructor, extreme care should be exercised in its use.
0574 * The thread stack size necessary to perform a given computation will
0575 * likely vary from one JRE implementation to another. In light of this
0576 * variation, careful tuning of the stack size parameter may be required,
0577 * and the tuning may need to be repeated for each JRE implementation on
0578 * which an application is to run.</i>
0579 *
0580 * <p>Implementation note: Java platform implementers are encouraged to
0581 * document their implementation's behavior with respect to the
0582 * <tt>stackSize parameter</tt>.
0583 *
0584 * @param group the thread group.
0585 * @param target the object whose <code>run</code> method is called.
0586 * @param name the name of the new thread.
0587 * @param stackSize the desired stack size for the new thread, or
0588 * zero to indicate that this parameter is to be ignored.
0589 * @exception SecurityException if the current thread cannot create a
0590 * thread in the specified thread group.
0591 * @since 1.4
0592 */
0593 public Thread(ThreadGroup group, Runnable target, String name,
0594 long stackSize) {
0595 init(group, target, name, stackSize);
0596 }
0597
0598 /**
0599 * Causes this thread to begin execution; the Java Virtual Machine
0600 * calls the <code>run</code> method of this thread.
0601 * <p>
0602 * The result is that two threads are running concurrently: the
0603 * current thread (which returns from the call to the
0604 * <code>start</code> method) and the other thread (which executes its
0605 * <code>run</code> method).
0606 * <p>
0607 * It is never legal to start a thread more than once.
0608 * In particular, a thread may not be restarted once it has completed
0609 * execution.
0610 *
0611 * @exception IllegalThreadStateException if the thread was already
0612 * started.
0613 * @see #run()
0614 * @see #stop()
0615 */
0616 public synchronized void start() {
0617 /**
0618 * This method is not invoked for the main method thread or "system"
0619 * group threads created/set up by the VM. Any new functionality added
0620 * to this method in the future may have to also be added to the VM.
0621 *
0622 * A zero status value corresponds to state "NEW".
0623 */
0624 if (threadStatus != 0)
0625 throw new IllegalThreadStateException();
0626 group.add(this );
0627 start0();
0628 if (stopBeforeStart) {
0629 stop0(throwableFromStop);
0630 }
0631 }
0632
0633 private native void start0();
0634
0635 /**
0636 * If this thread was constructed using a separate
0637 * <code>Runnable</code> run object, then that
0638 * <code>Runnable</code> object's <code>run</code> method is called;
0639 * otherwise, this method does nothing and returns.
0640 * <p>
0641 * Subclasses of <code>Thread</code> should override this method.
0642 *
0643 * @see #start()
0644 * @see #stop()
0645 * @see #Thread(ThreadGroup, Runnable, String)
0646 */
0647 public void run() {
0648 if (target != null) {
0649 target.run();
0650 }
0651 }
0652
0653 /**
0654 * This method is called by the system to give a Thread
0655 * a chance to clean up before it actually exits.
0656 */
0657 private void exit() {
0658 if (group != null) {
0659 group.remove(this );
0660 group = null;
0661 }
0662 /* Aggressively null out all reference fields: see bug 4006245 */
0663 target = null;
0664 /* Speed the release of some of these resources */
0665 threadLocals = null;
0666 inheritableThreadLocals = null;
0667 inheritedAccessControlContext = null;
0668 blocker = null;
0669 uncaughtExceptionHandler = null;
0670 }
0671
0672 /**
0673 * Forces the thread to stop executing.
0674 * <p>
0675 * If there is a security manager installed, its <code>checkAccess</code>
0676 * method is called with <code>this</code>
0677 * as its argument. This may result in a
0678 * <code>SecurityException</code> being raised (in the current thread).
0679 * <p>
0680 * If this thread is different from the current thread (that is, the current
0681 * thread is trying to stop a thread other than itself), the
0682 * security manager's <code>checkPermission</code> method (with a
0683 * <code>RuntimePermission("stopThread")</code> argument) is called in
0684 * addition.
0685 * Again, this may result in throwing a
0686 * <code>SecurityException</code> (in the current thread).
0687 * <p>
0688 * The thread represented by this thread is forced to stop whatever
0689 * it is doing abnormally and to throw a newly created
0690 * <code>ThreadDeath</code> object as an exception.
0691 * <p>
0692 * It is permitted to stop a thread that has not yet been started.
0693 * If the thread is eventually started, it immediately terminates.
0694 * <p>
0695 * An application should not normally try to catch
0696 * <code>ThreadDeath</code> unless it must do some extraordinary
0697 * cleanup operation (note that the throwing of
0698 * <code>ThreadDeath</code> causes <code>finally</code> clauses of
0699 * <code>try</code> statements to be executed before the thread
0700 * officially dies). If a <code>catch</code> clause catches a
0701 * <code>ThreadDeath</code> object, it is important to rethrow the
0702 * object so that the thread actually dies.
0703 * <p>
0704 * The top-level error handler that reacts to otherwise uncaught
0705 * exceptions does not print out a message or otherwise notify the
0706 * application if the uncaught exception is an instance of
0707 * <code>ThreadDeath</code>.
0708 *
0709 * @exception SecurityException if the current thread cannot
0710 * modify this thread.
0711 * @see #interrupt()
0712 * @see #checkAccess()
0713 * @see #run()
0714 * @see #start()
0715 * @see ThreadDeath
0716 * @see ThreadGroup#uncaughtException(Thread,Throwable)
0717 * @see SecurityManager#checkAccess(Thread)
0718 * @see SecurityManager#checkPermission
0719 * @deprecated This method is inherently unsafe. Stopping a thread with
0720 * Thread.stop causes it to unlock all of the monitors that it
0721 * has locked (as a natural consequence of the unchecked
0722 * <code>ThreadDeath</code> exception propagating up the stack). If
0723 * any of the objects previously protected by these monitors were in
0724 * an inconsistent state, the damaged objects become visible to
0725 * other threads, potentially resulting in arbitrary behavior. Many
0726 * uses of <code>stop</code> should be replaced by code that simply
0727 * modifies some variable to indicate that the target thread should
0728 * stop running. The target thread should check this variable
0729 * regularly, and return from its run method in an orderly fashion
0730 * if the variable indicates that it is to stop running. If the
0731 * target thread waits for long periods (on a condition variable,
0732 * for example), the <code>interrupt</code> method should be used to
0733 * interrupt the wait.
0734 * For more information, see
0735 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
0736 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
0737 */
0738 @Deprecated
0739 public final void stop() {
0740 // If the thread is already dead, return.
0741 // A zero status value corresponds to "NEW".
0742 if ((threadStatus != 0) && !isAlive()) {
0743 return;
0744 }
0745 stop1(new ThreadDeath());
0746 }
0747
0748 /**
0749 * Forces the thread to stop executing.
0750 * <p>
0751 * If there is a security manager installed, the <code>checkAccess</code>
0752 * method of this thread is called, which may result in a
0753 * <code>SecurityException</code> being raised (in the current thread).
0754 * <p>
0755 * If this thread is different from the current thread (that is, the current
0756 * thread is trying to stop a thread other than itself) or
0757 * <code>obj</code> is not an instance of <code>ThreadDeath</code>, the
0758 * security manager's <code>checkPermission</code> method (with the
0759 * <code>RuntimePermission("stopThread")</code> argument) is called in
0760 * addition.
0761 * Again, this may result in throwing a
0762 * <code>SecurityException</code> (in the current thread).
0763 * <p>
0764 * If the argument <code>obj</code> is null, a
0765 * <code>NullPointerException</code> is thrown (in the current thread).
0766 * <p>
0767 * The thread represented by this thread is forced to stop
0768 * whatever it is doing abnormally and to throw the
0769 * <code>Throwable</code> object <code>obj</code> as an exception. This
0770 * is an unusual action to take; normally, the <code>stop</code> method
0771 * that takes no arguments should be used.
0772 * <p>
0773 * It is permitted to stop a thread that has not yet been started.
0774 * If the thread is eventually started, it immediately terminates.
0775 *
0776 * @param obj the Throwable object to be thrown.
0777 * @exception SecurityException if the current thread cannot modify
0778 * this thread.
0779 * @throws NullPointerException if obj is <tt>null</tt>.
0780 * @see #interrupt()
0781 * @see #checkAccess()
0782 * @see #run()
0783 * @see #start()
0784 * @see #stop()
0785 * @see SecurityManager#checkAccess(Thread)
0786 * @see SecurityManager#checkPermission
0787 * @deprecated This method is inherently unsafe. See {@link #stop()}
0788 * for details. An additional danger of this
0789 * method is that it may be used to generate exceptions that the
0790 * target thread is unprepared to handle (including checked
0791 * exceptions that the thread could not possibly throw, were it
0792 * not for this method).
0793 * For more information, see
0794 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
0795 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
0796 */
0797 @Deprecated
0798 public final synchronized void stop(Throwable obj) {
0799 stop1(obj);
0800 }
0801
0802 /**
0803 * Common impl for stop() and stop(Throwable).
0804 */
0805 private final synchronized void stop1(Throwable th) {
0806 SecurityManager security = System.getSecurityManager();
0807 if (security != null) {
0808 checkAccess();
0809 if ((this != Thread.currentThread())
0810 || (!(th instanceof ThreadDeath))) {
0811 security
0812 .checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
0813 }
0814 }
0815 // A zero status value corresponds to "NEW"
0816 if (threadStatus != 0) {
0817 resume(); // Wake up thread if it was suspended; no-op otherwise
0818 stop0(th);
0819 } else {
0820
0821 // Must do the null arg check that the VM would do with stop0
0822 if (th == null) {
0823 throw new NullPointerException();
0824 }
0825
0826 // Remember this stop attempt for if/when start is used
0827 stopBeforeStart = true;
0828 throwableFromStop = th;
0829 }
0830 }
0831
0832 /**
0833 * Interrupts this thread.
0834 *
0835 * <p> Unless the current thread is interrupting itself, which is
0836 * always permitted, the {@link #checkAccess() checkAccess} method
0837 * of this thread is invoked, which may cause a {@link
0838 * SecurityException} to be thrown.
0839 *
0840 * <p> If this thread is blocked in an invocation of the {@link
0841 * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
0842 * Object#wait(long, int) wait(long, int)} methods of the {@link Object}
0843 * class, or of the {@link #join()}, {@link #join(long)}, {@link
0844 * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
0845 * methods of this class, then its interrupt status will be cleared and it
0846 * will receive an {@link InterruptedException}.
0847 *
0848 * <p> If this thread is blocked in an I/O operation upon an {@link
0849 * java.nio.channels.InterruptibleChannel </code>interruptible
0850 * channel<code>} then the channel will be closed, the thread's interrupt
0851 * status will be set, and the thread will receive a {@link
0852 * java.nio.channels.ClosedByInterruptException}.
0853 *
0854 * <p> If this thread is blocked in a {@link java.nio.channels.Selector}
0855 * then the thread's interrupt status will be set and it will return
0856 * immediately from the selection operation, possibly with a non-zero
0857 * value, just as if the selector's {@link
0858 * java.nio.channels.Selector#wakeup wakeup} method were invoked.
0859 *
0860 * <p> If none of the previous conditions hold then this thread's interrupt
0861 * status will be set. </p>
0862 *
0863 * <p> Interrupting a thread that is not alive need not have any effect.
0864 *
0865 * @throws SecurityException
0866 * if the current thread cannot modify this thread
0867 *
0868 * @revised 6.0
0869 * @spec JSR-51
0870 */
0871 public void interrupt() {
0872 if (this != Thread.currentThread())
0873 checkAccess();
0874
0875 synchronized (blockerLock) {
0876 Interruptible b = blocker;
0877 if (b != null) {
0878 interrupt0(); // Just to set the interrupt flag
0879 b.interrupt();
0880 return;
0881 }
0882 }
0883 interrupt0();
0884 }
0885
0886 /**
0887 * Tests whether the current thread has been interrupted. The
0888 * <i>interrupted status</i> of the thread is cleared by this method. In
0889 * other words, if this method were to be called twice in succession, the
0890 * second call would return false (unless the current thread were
0891 * interrupted again, after the first call had cleared its interrupted
0892 * status and before the second call had examined it).
0893 *
0894 * <p>A thread interruption ignored because a thread was not alive
0895 * at the time of the interrupt will be reflected by this method
0896 * returning false.
0897 *
0898 * @return <code>true</code> if the current thread has been interrupted;
0899 * <code>false</code> otherwise.
0900 * @see #isInterrupted()
0901 * @revised 6.0
0902 */
0903 public static boolean interrupted() {
0904 return currentThread().isInterrupted(true);
0905 }
0906
0907 /**
0908 * Tests whether this thread has been interrupted. The <i>interrupted
0909 * status</i> of the thread is unaffected by this method.
0910 *
0911 * <p>A thread interruption ignored because a thread was not alive
0912 * at the time of the interrupt will be reflected by this method
0913 * returning false.
0914 *
0915 * @return <code>true</code> if this thread has been interrupted;
0916 * <code>false</code> otherwise.
0917 * @see #interrupted()
0918 * @revised 6.0
0919 */
0920 public boolean isInterrupted() {
0921 return isInterrupted(false);
0922 }
0923
0924 /**
0925 * Tests if some Thread has been interrupted. The interrupted state
0926 * is reset or not based on the value of ClearInterrupted that is
0927 * passed.
0928 */
0929 private native boolean isInterrupted(boolean ClearInterrupted);
0930
0931 /**
0932 * Throws {@link NoSuchMethodError}.
0933 *
0934 * @deprecated This method was originally designed to destroy this
0935 * thread without any cleanup. Any monitors it held would have
0936 * remained locked. However, the method was never implemented.
0937 * If if were to be implemented, it would be deadlock-prone in
0938 * much the manner of {@link #suspend}. If the target thread held
0939 * a lock protecting a critical system resource when it was
0940 * destroyed, no thread could ever access this resource again.
0941 * If another thread ever attempted to lock this resource, deadlock
0942 * would result. Such deadlocks typically manifest themselves as
0943 * "frozen" processes. For more information, see
0944 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">
0945 * Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
0946 * @throws NoSuchMethodError always
0947 */
0948 @Deprecated
0949 public void destroy() {
0950 throw new NoSuchMethodError();
0951 }
0952
0953 /**
0954 * Tests if this thread is alive. A thread is alive if it has
0955 * been started and has not yet died.
0956 *
0957 * @return <code>true</code> if this thread is alive;
0958 * <code>false</code> otherwise.
0959 */
0960 public final native boolean isAlive();
0961
0962 /**
0963 * Suspends this thread.
0964 * <p>
0965 * First, the <code>checkAccess</code> method of this thread is called
0966 * with no arguments. This may result in throwing a
0967 * <code>SecurityException </code>(in the current thread).
0968 * <p>
0969 * If the thread is alive, it is suspended and makes no further
0970 * progress unless and until it is resumed.
0971 *
0972 * @exception SecurityException if the current thread cannot modify
0973 * this thread.
0974 * @see #checkAccess
0975 * @deprecated This method has been deprecated, as it is
0976 * inherently deadlock-prone. If the target thread holds a lock on the
0977 * monitor protecting a critical system resource when it is suspended, no
0978 * thread can access this resource until the target thread is resumed. If
0979 * the thread that would resume the target thread attempts to lock this
0980 * monitor prior to calling <code>resume</code>, deadlock results. Such
0981 * deadlocks typically manifest themselves as "frozen" processes.
0982 * For more information, see
0983 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
0984 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
0985 */
0986 @Deprecated
0987 public final void suspend() {
0988 checkAccess();
0989 suspend0();
0990 }
0991
0992 /**
0993 * Resumes a suspended thread.
0994 * <p>
0995 * First, the <code>checkAccess</code> method of this thread is called
0996 * with no arguments. This may result in throwing a
0997 * <code>SecurityException</code> (in the current thread).
0998 * <p>
0999 * If the thread is alive but suspended, it is resumed and is
1000 * permitted to make progress in its execution.
1001 *
1002 * @exception SecurityException if the current thread cannot modify this
1003 * thread.
1004 * @see #checkAccess
1005 * @see #suspend()
1006 * @deprecated This method exists solely for use with {@link #suspend},
1007 * which has been deprecated because it is deadlock-prone.
1008 * For more information, see
1009 * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
1010 * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1011 */
1012 @Deprecated
1013 public final void resume() {
1014 checkAccess();
1015 resume0();
1016 }
1017
1018 /**
1019 * Changes the priority of this thread.
1020 * <p>
1021 * First the <code>checkAccess</code> method of this thread is called
1022 * with no arguments. This may result in throwing a
1023 * <code>SecurityException</code>.
1024 * <p>
1025 * Otherwise, the priority of this thread is set to the smaller of
1026 * the specified <code>newPriority</code> and the maximum permitted
1027 * priority of the thread's thread group.
1028 *
1029 * @param newPriority priority to set this thread to
1030 * @exception IllegalArgumentException If the priority is not in the
1031 * range <code>MIN_PRIORITY</code> to
1032 * <code>MAX_PRIORITY</code>.
1033 * @exception SecurityException if the current thread cannot modify
1034 * this thread.
1035 * @see #getPriority
1036 * @see #checkAccess()
1037 * @see #getThreadGroup()
1038 * @see #MAX_PRIORITY
1039 * @see #MIN_PRIORITY
1040 * @see ThreadGroup#getMaxPriority()
1041 */
1042 public final void setPriority(int newPriority) {
1043 ThreadGroup g;
1044 checkAccess();
1045 if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
1046 throw new IllegalArgumentException();
1047 }
1048 if ((g = getThreadGroup()) != null) {
1049 if (newPriority > g.getMaxPriority()) {
1050 newPriority = g.getMaxPriority();
1051 }
1052 setPriority0(priority = newPriority);
1053 }
1054 }
1055
1056 /**
1057 * Returns this thread's priority.
1058 *
1059 * @return this thread's priority.
1060 * @see #setPriority
1061 */
1062 public final int getPriority() {
1063 return priority;
1064 }
1065
1066 /**
1067 * Changes the name of this thread to be equal to the argument
1068 * <code>name</code>.
1069 * <p>
1070 * First the <code>checkAccess</code> method of this thread is called
1071 * with no arguments. This may result in throwing a
1072 * <code>SecurityException</code>.
1073 *
1074 * @param name the new name for this thread.
1075 * @exception SecurityException if the current thread cannot modify this
1076 * thread.
1077 * @see #getName
1078 * @see #checkAccess()
1079 */
1080 public final void setName(String name) {
1081 checkAccess();
1082 this .name = name.toCharArray();
1083 }
1084
1085 /**
1086 * Returns this thread's name.
1087 *
1088 * @return this thread's name.
1089 * @see #setName(String)
1090 */
1091 public final String getName() {
1092 return String.valueOf(name);
1093 }
1094
1095 /**
1096 * Returns the thread group to which this thread belongs.
1097 * This method returns null if this thread has died
1098 * (been stopped).
1099 *
1100 * @return this thread's thread group.
1101 */
1102 public final ThreadGroup getThreadGroup() {
1103 return group;
1104 }
1105
1106 /**
1107 * Returns the number of active threads in the current thread's thread
1108 * group.
1109 *
1110 * @return the number of active threads in the current thread's thread
1111 * group.
1112 */
1113 public static int activeCount() {
1114 return currentThread().getThreadGroup().activeCount();
1115 }
1116
1117 /**
1118 * Copies into the specified array every active thread in
1119 * the current thread's thread group and its subgroups. This method simply
1120 * calls the <code>enumerate</code> method of the current thread's thread
1121 * group with the array argument.
1122 * <p>
1123 * First, if there is a security manager, that <code>enumerate</code>
1124 * method calls the security
1125 * manager's <code>checkAccess</code> method
1126 * with the thread group as its argument. This may result
1127 * in throwing a <code>SecurityException</code>.
1128 *
1129 * @param tarray an array of Thread objects to copy to
1130 * @return the number of threads put into the array
1131 * @exception SecurityException if a security manager exists and its
1132 * <code>checkAccess</code> method doesn't allow the operation.
1133 * @see ThreadGroup#enumerate(Thread[])
1134 * @see SecurityManager#checkAccess(ThreadGroup)
1135 */
1136 public static int enumerate(Thread tarray[]) {
1137 return currentThread().getThreadGroup().enumerate(tarray);
1138 }
1139
1140 /**
1141 * Counts the number of stack frames in this thread. The thread must
1142 * be suspended.
1143 *
1144 * @return the number of stack frames in this thread.
1145 * @exception IllegalThreadStateException if this thread is not
1146 * suspended.
1147 * @deprecated The definition of this call depends on {@link #suspend},
1148 * which is deprecated. Further, the results of this call
1149 * were never well-defined.
1150 */
1151 @Deprecated
1152 public native int countStackFrames();
1153
1154 /**
1155 * Waits at most {@code millis} milliseconds for this thread to
1156 * die. A timeout of {@code 0} means to wait forever.
1157 *
1158 * <p> This implementation uses a loop of {@code this.wait} calls
1159 * conditioned on {@code this.isAlive}. As a thread terminates the
1160 * {@code this.notifyAll} method is invoked. It is recommended that
1161 * applications not use {@code wait}, {@code notify}, or
1162 * {@code notifyAll} on {@code Thread} instances.
1163 *
1164 * @param millis
1165 * the time to wait in milliseconds
1166 *
1167 * @throws IllegalArgumentException
1168 * if the value of {@code millis} is negative
1169 *
1170 * @throws InterruptedException
1171 * if any thread has interrupted the current thread. The
1172 * <i>interrupted status</i> of the current thread is
1173 * cleared when this exception is thrown.
1174 */
1175 public final synchronized void join(long millis)
1176 throws InterruptedException {
1177 long base = System.currentTimeMillis();
1178 long now = 0;
1179
1180 if (millis < 0) {
1181 throw new IllegalArgumentException(
1182 "timeout value is negative");
1183 }
1184
1185 if (millis == 0) {
1186 while (isAlive()) {
1187 wait(0);
1188 }
1189 } else {
1190 while (isAlive()) {
1191 long delay = millis - now;
1192 if (delay <= 0) {
1193 break;
1194 }
1195 wait(delay);
1196 now = System.currentTimeMillis() - base;
1197 }
1198 }
1199 }
1200
1201 /**
1202 * Waits at most {@code millis} milliseconds plus
1203 * {@code nanos} nanoseconds for this thread to die.
1204 *
1205 * <p> This implementation uses a loop of {@code this.wait} calls
1206 * conditioned on {@code this.isAlive}. As a thread terminates the
1207 * {@code this.notifyAll} method is invoked. It is recommended that
1208 * applications not use {@code wait}, {@code notify}, or
1209 * {@code notifyAll} on {@code Thread} instances.
1210 *
1211 * @param millis
1212 * the time to wait in milliseconds
1213 *
1214 * @param nanos
1215 * {@code 0-999999} additional nanoseconds to wait
1216 *
1217 * @throws IllegalArgumentException
1218 * if the value of {@code millis} is negative, or the value
1219 * of {@code nanos} is not in the range {@code 0-999999}
1220 *
1221 * @throws InterruptedException
1222 * if any thread has interrupted the current thread. The
1223 * <i>interrupted status</i> of the current thread is
1224 * cleared when this exception is thrown.
1225 */
1226 public final synchronized void join(long millis, int nanos)
1227 throws InterruptedException {
1228
1229 if (millis < 0) {
1230 throw new IllegalArgumentException(
1231 "timeout value is negative");
1232 }
1233
1234 if (nanos < 0 || nanos > 999999) {
1235 throw new IllegalArgumentException(
1236 "nanosecond timeout value out of range");
1237 }
1238
1239 if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
1240 millis++;
1241 }
1242
1243 join(millis);
1244 }
1245
1246 /**
1247 * Waits for this thread to die.
1248 *
1249 * <p> An invocation of this method behaves in exactly the same
1250 * way as the invocation
1251 *
1252 * <blockquote>
1253 * {@linkplain #join(long) join}{@code (0)}
1254 * </blockquote>
1255 *
1256 * @throws InterruptedException
1257 * if any thread has interrupted the current thread. The
1258 * <i>interrupted status</i> of the current thread is
1259 * cleared when this exception is thrown.
1260 */
1261 public final void join() throws InterruptedException {
1262 join(0);
1263 }
1264
1265 /**
1266 * Prints a stack trace of the current thread to the standard error stream.
1267 * This method is used only for debugging.
1268 *
1269 * @see Throwable#printStackTrace()
1270 */
1271 public static void dumpStack() {
1272 new Exception("Stack trace").printStackTrace();
1273 }
1274
1275 /**
1276 * Marks this thread as either a {@linkplain #isDaemon daemon} thread
1277 * or a user thread. The Java Virtual Machine exits when the only
1278 * threads running are all daemon threads.
1279 *
1280 * <p> This method must be invoked before the thread is started.
1281 *
1282 * @param on
1283 * if {@code true}, marks this thread as a daemon thread
1284 *
1285 * @throws IllegalThreadStateException
1286 * if this thread is {@linkplain #isAlive alive}
1287 *
1288 * @throws SecurityException
1289 * if {@link #checkAccess} determines that the current
1290 * thread cannot modify this thread
1291 */
1292 public final void setDaemon(boolean on) {
1293 checkAccess();
1294 if (isAlive()) {
1295 throw new IllegalThreadStateException();
1296 }
1297 daemon = on;
1298 }
1299
1300 /**
1301 * Tests if this thread is a daemon thread.
1302 *
1303 * @return <code>true</code> if this thread is a daemon thread;
1304 * <code>false</code> otherwise.
1305 * @see #setDaemon(boolean)
1306 */
1307 public final boolean isDaemon() {
1308 return daemon;
1309 }
1310
1311 /**
1312 * Determines if the currently running thread has permission to
1313 * modify this thread.
1314 * <p>
1315 * If there is a security manager, its <code>checkAccess</code> method
1316 * is called with this thread as its argument. This may result in
1317 * throwing a <code>SecurityException</code>.
1318 *
1319 * @exception SecurityException if the current thread is not allowed to
1320 * access this thread.
1321 * @see SecurityManager#checkAccess(Thread)
1322 */
1323 public final void checkAccess() {
1324 SecurityManager security = System.getSecurityManager();
1325 if (security != null) {
1326 security.checkAccess(this );
1327 }
1328 }
1329
1330 /**
1331 * Returns a string representation of this thread, including the
1332 * thread's name, priority, and thread group.
1333 *
1334 * @return a string representation of this thread.
1335 */
1336 public String toString() {
1337 ThreadGroup group = getThreadGroup();
1338 if (group != null) {
1339 return "Thread[" + getName() + "," + getPriority() + ","
1340 + group.getName() + "]";
1341 } else {
1342 return "Thread[" + getName() + "," + getPriority() + ","
1343 + "" + "]";
1344 }
1345 }
1346
1347 /**
1348 * Returns the context ClassLoader for this Thread. The context
1349 * ClassLoader is provided by the creator of the thread for use
1350 * by code running in this thread when loading classes and resources.
1351 * If not set, the default is the ClassLoader context of the parent
1352 * Thread. The context ClassLoader of the primordial thread is
1353 * typically set to the class loader used to load the application.
1354 *
1355 * <p>First, if there is a security manager, and the caller's class
1356 * loader is not null and the caller's class loader is not the same as or
1357 * an ancestor of the context class loader for the thread whose
1358 * context class loader is being requested, then the security manager's
1359 * <code>checkPermission</code>
1360 * method is called with a
1361 * <code>RuntimePermission("getClassLoader")</code> permission
1362 * to see if it's ok to get the context ClassLoader..
1363 *
1364 * @return the context ClassLoader for this Thread
1365 *
1366 * @throws SecurityException
1367 * if a security manager exists and its
1368 * <code>checkPermission</code> method doesn't allow
1369 * getting the context ClassLoader.
1370 * @see #setContextClassLoader
1371 * @see SecurityManager#checkPermission
1372 * @see RuntimePermission
1373 *
1374 * @since 1.2
1375 */
1376 public ClassLoader getContextClassLoader() {
1377 if (contextClassLoader == null)
1378 return null;
1379 SecurityManager sm = System.getSecurityManager();
1380 if (sm != null) {
1381 ClassLoader ccl = ClassLoader.getCallerClassLoader();
1382 if (ccl != null && ccl != contextClassLoader
1383 && !contextClassLoader.isAncestor(ccl)) {
1384 sm
1385 .checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
1386 }
1387 }
1388 return contextClassLoader;
1389 }
1390
1391 /**
1392 * Sets the context ClassLoader for this Thread. The context
1393 * ClassLoader can be set when a thread is created, and allows
1394 * the creator of the thread to provide the appropriate class loader
1395 * to code running in the thread when loading classes and resources.
1396 *
1397 * <p>First, if there is a security manager, its <code>checkPermission</code>
1398 * method is called with a
1399 * <code>RuntimePermission("setContextClassLoader")</code> permission
1400 * to see if it's ok to set the context ClassLoader..
1401 *
1402 * @param cl the context ClassLoader for this Thread
1403 *
1404 * @exception SecurityException if the current thread cannot set the
1405 * context ClassLoader.
1406 * @see #getContextClassLoader
1407 * @see SecurityManager#checkPermission
1408 * @see RuntimePermission
1409 *
1410 * @since 1.2
1411 */
1412 public void setContextClassLoader(ClassLoader cl) {
1413 SecurityManager sm = System.getSecurityManager();
1414 if (sm != null) {
1415 sm.checkPermission(new RuntimePermission(
1416 "setContextClassLoader"));
1417 }
1418 contextClassLoader = cl;
1419 }
1420
1421 /**
1422 * Returns <tt>true</tt> if and only if the current thread holds the
1423 * monitor lock on the specified object.
1424 *
1425 * <p>This method is designed to allow a program to assert that
1426 * the current thread already holds a specified lock:
1427 * <pre>
1428 * assert Thread.holdsLock(obj);
1429 * </pre>
1430 *
1431 * @param obj the object on which to test lock ownership
1432 * @throws NullPointerException if obj is <tt>null</tt>
1433 * @return <tt>true</tt> if the current thread holds the monitor lock on
1434 * the specified object.
1435 * @since 1.4
1436 */
1437 public static native boolean holdsLock(Object obj);
1438
1439 private static final StackTraceElement[] EMPTY_STACK_TRACE = new StackTraceElement[0];
1440
1441 /**
1442 * Returns an array of stack trace elements representing the stack dump
1443 * of this thread. This method will return a zero-length array if
1444 * this thread has not started, has started but has not yet been
1445 * scheduled to run by the system, or has terminated.
1446 * If the returned array is of non-zero length then the first element of
1447 * the array represents the top of the stack, which is the most recent
1448 * method invocation in the sequence. The last element of the array
1449 * represents the bottom of the stack, which is the least recent method
1450 * invocation in the sequence.
1451 *
1452 * <p>If there is a security manager, and this thread is not
1453 * the current thread, then the security manager's
1454 * <tt>checkPermission</tt> method is called with a
1455 * <tt>RuntimePermission("getStackTrace")</tt> permission
1456 * to see if it's ok to get the stack trace.
1457 *
1458 * <p>Some virtual machines may, under some circumstances, omit one
1459 * or more stack frames from the stack trace. In the extreme case,
1460 * a virtual machine that has no stack trace information concerning
1461 * this thread is permitted to return a zero-length array from this
1462 * method.
1463 *
1464 * @return an array of <tt>StackTraceElement</tt>,
1465 * each represents one stack frame.
1466 *
1467 * @throws SecurityException
1468 * if a security manager exists and its
1469 * <tt>checkPermission</tt> method doesn't allow
1470 * getting the stack trace of thread.
1471 * @see SecurityManager#checkPermission
1472 * @see RuntimePermission
1473 * @see Throwable#getStackTrace
1474 *
1475 * @since 1.5
1476 */
1477 public StackTraceElement[] getStackTrace() {
1478 if (this != Thread.currentThread()) {
1479 // check for getStackTrace permission
1480 SecurityManager security = System.getSecurityManager();
1481 if (security != null) {
1482 security
1483 .checkPermission(SecurityConstants.GET_STACK_TRACE_PERMISSION);
1484 }
1485 // optimization so we do not call into the vm for threads that
1486 // have not yet started or have terminated
1487 if (!isAlive()) {
1488 return EMPTY_STACK_TRACE;
1489 }
1490 StackTraceElement[][] stackTraceArray = dumpThreads(new Thread[] { this });
1491 StackTraceElement[] stackTrace = stackTraceArray[0];
1492 // a thread that was alive during the previous isAlive call may have
1493 // since terminated, therefore not having a stacktrace.
1494 if (stackTrace == null) {
1495 stackTrace = EMPTY_STACK_TRACE;
1496 }
1497 return stackTrace;
1498 } else {
1499 // Don't need JVM help for current thread
1500 return (new Exception()).getStackTrace();
1501 }
1502 }
1503
1504 /**
1505 * Returns a map of stack traces for all live threads.
1506 * The map keys are threads and each map value is an array of
1507 * <tt>StackTraceElement</tt> that represents the stack dump
1508 * of the corresponding <tt>Thread</tt>.
1509 * The returned stack traces are in the format specified for
1510 * the {@link #getStackTrace getStackTrace} method.
1511 *
1512 * <p>The threads may be executing while this method is called.
1513 * The stack trace of each thread only represents a snapshot and
1514 * each stack trace may be obtained at different time. A zero-length
1515 * array will be returned in the map value if the virtual machine has
1516 * no stack trace information about a thread.
1517 *
1518 * <p>If there is a security manager, then the security manager's
1519 * <tt>checkPermission</tt> method is called with a
1520 * <tt>RuntimePermission("getStackTrace")</tt> permission as well as
1521 * <tt>RuntimePermission("modifyThreadGroup")</tt> permission
1522 * to see if it is ok to get the stack trace of all threads.
1523 *
1524 * @return a <tt>Map</tt> from <tt>Thread</tt> to an array of
1525 * <tt>StackTraceElement</tt> that represents the stack trace of
1526 * the corresponding thread.
1527 *
1528 * @throws SecurityException
1529 * if a security manager exists and its
1530 * <tt>checkPermission</tt> method doesn't allow
1531 * getting the stack trace of thread.
1532 * @see #getStackTrace
1533 * @see SecurityManager#checkPermission
1534 * @see RuntimePermission
1535 * @see Throwable#getStackTrace
1536 *
1537 * @since 1.5
1538 */
1539 public static Map<Thread, StackTraceElement[]> getAllStackTraces() {
1540 // check for getStackTrace permission
1541 SecurityManager security = System.getSecurityManager();
1542 if (security != null) {
1543 security
1544 .checkPermission(SecurityConstants.GET_STACK_TRACE_PERMISSION);
1545 security
1546 .checkPermission(SecurityConstants.MODIFY_THREADGROUP_PERMISSION);
1547 }
1548
1549 // Get a snapshot of the list of all threads
1550 Thread[] threads = getThreads();
1551 StackTraceElement[][] traces = dumpThreads(threads);
1552 Map<Thread, StackTraceElement[]> m = new HashMap<Thread, StackTraceElement[]>(
1553 threads.length);
1554 for (int i = 0; i < threads.length; i++) {
1555 StackTraceElement[] stackTrace = traces[i];
1556 if (stackTrace != null) {
1557 m.put(threads[i], stackTrace);
1558 }
1559 // else terminated so we don't put it in the map
1560 }
1561 return m;
1562 }
1563
1564 private static final RuntimePermission SUBCLASS_IMPLEMENTATION_PERMISSION = new RuntimePermission(
1565 "enableContextClassLoaderOverride");
1566
1567 /** cache of subclass security audit results */
1568 private static final SoftCache subclassAudits = new SoftCache(10);
1569
1570 /**
1571 * Verifies that this (possibly subclass) instance can be constructed
1572 * without violating security constraints: the subclass must not override
1573 * security-sensitive non-final methods, or else the
1574 * "enableContextClassLoaderOverride" RuntimePermission is checked.
1575 */
1576 private static boolean isCCLOverridden(Class cl) {
1577 if (cl == Thread.class)
1578 return false;
1579 Boolean result = null;
1580 synchronized (subclassAudits) {
1581 result = (Boolean) subclassAudits.get(cl);
1582 if (result == null) {
1583 /*
1584 * Note: only new Boolean instances (i.e., not Boolean.TRUE or
1585 * Boolean.FALSE) must be used as cache values, otherwise cache
1586 * entry will pin associated class.
1587 */
1588 result = new Boolean(auditSubclass(cl));
1589 subclassAudits.put(cl, result);
1590 }
1591 }
1592 return result.booleanValue();
1593 }
1594
1595 /**
1596 * Performs reflective checks on given subclass to verify that it doesn't
1597 * override security-sensitive non-final methods. Returns true if the
1598 * subclass overrides any of the methods, false otherwise.
1599 */
1600 private static boolean auditSubclass(final Class subcl) {
1601 Boolean result = (Boolean) AccessController
1602 .doPrivileged(new PrivilegedAction() {
1603 public Object run() {
1604 for (Class cl = subcl; cl != Thread.class; cl = cl
1605 .getSuperclass()) {
1606 try {
1607 cl.getDeclaredMethod(
1608 "getContextClassLoader",
1609 new Class[0]);
1610 return Boolean.TRUE;
1611 } catch (NoSuchMethodException ex) {
1612 }
1613 try {
1614 Class[] params = { ClassLoader.class };
1615 cl
1616 .getDeclaredMethod(
1617 "setContextClassLoader",
1618 params);
1619 return Boolean.TRUE;
1620 } catch (NoSuchMethodException ex) {
1621 }
1622 }
1623 return Boolean.FALSE;
1624 }
1625 });
1626 return result.booleanValue();
1627 }
1628
1629 private native static StackTraceElement[][] dumpThreads(
1630 Thread[] threads);
1631
1632 private native static Thread[] getThreads();
1633
1634 /**
1635 * Returns the identifier of this Thread. The thread ID is a positive
1636 * <tt>long</tt> number generated when this thread was created.
1637 * The thread ID is unique and remains unchanged during its lifetime.
1638 * When a thread is terminated, this thread ID may be reused.
1639 *
1640 * @return this thread's ID.
1641 * @since 1.5
1642 */
1643 public long getId() {
1644 return tid;
1645 }
1646
1647 /**
1648 * A thread state. A thread can be in one of the following states:
1649 * <ul>
1650 * <li>{@link #NEW}<br>
1651 * A thread that has not yet started is in this state.
1652 * </li>
1653 * <li>{@link #RUNNABLE}<br>
1654 * A thread executing in the Java virtual machine is in this state.
1655 * </li>
1656 * <li>{@link #BLOCKED}<br>
1657 * A thread that is blocked waiting for a monitor lock
1658 * is in this state.
1659 * </li>
1660 * <li>{@link #WAITING}<br>
1661 * A thread that is waiting indefinitely for another thread to
1662 * perform a particular action is in this state.
1663 * </li>
1664 * <li>{@link #TIMED_WAITING}<br>
1665 * A thread that is waiting for another thread to perform an action
1666 * for up to a specified waiting time is in this state.
1667 * </li>
1668 * <li>{@link #TERMINATED}<br>
1669 * A thread that has exited is in this state.
1670 * </li>
1671 * </ul>
1672 *
1673 * <p>
1674 * A thread can be in only one state at a given point in time.
1675 * These states are virtual machine states which do not reflect
1676 * any operating system thread states.
1677 *
1678 * @since 1.5
1679 * @see #getState
1680 */
1681 public enum State {
1682 /**
1683 * Thread state for a thread which has not yet started.
1684 */
1685 NEW,
1686
1687 /**
1688 * Thread state for a runnable thread. A thread in the runnable
1689 * state is executing in the Java virtual machine but it may
1690 * be waiting for other resources from the operating system
1691 * such as processor.
1692 */
1693 RUNNABLE,
1694
1695 /**
1696 * Thread state for a thread blocked waiting for a monitor lock.
1697 * A thread in the blocked state is waiting for a monitor lock
1698 * to enter a synchronized block/method or
1699 * reenter a synchronized block/method after calling
1700 * {@link Object#wait() Object.wait}.
1701 */
1702 BLOCKED,
1703
1704 /**
1705 * Thread state for a waiting thread.
1706 * A thread is in the waiting state due to calling one of the
1707 * following methods:
1708 * <ul>
1709 * <li>{@link Object#wait() Object.wait} with no timeout</li>
1710 * <li>{@link #join() Thread.join} with no timeout</li>
1711 * <li>{@link LockSupport#park() LockSupport.park}</li>
1712 * </ul>
1713 *
1714 * <p>A thread in the waiting state is waiting for another thread to
1715 * perform a particular action.
1716 *
1717 * For example, a thread that has called <tt>Object.wait()</tt>
1718 * on an object is waiting for another thread to call
1719 * <tt>Object.notify()</tt> or <tt>Object.notifyAll()</tt> on
1720 * that object. A thread that has called <tt>Thread.join()</tt>
1721 * is waiting for a specified thread to terminate.
1722 */
1723 WAITING,
1724
1725 /**
1726 * Thread state for a waiting thread with a specified waiting time.
1727 * A thread is in the timed waiting state due to calling one of
1728 * the following methods with a specified positive waiting time:
1729 * <ul>
1730 * <li>{@link #sleep Thread.sleep}</li>
1731 * <li>{@link Object#wait(long) Object.wait} with timeout</li>
1732 * <li>{@link #join(long) Thread.join} with timeout</li>
1733 * <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
1734 * <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
1735 * </ul>
1736 */
1737 TIMED_WAITING,
1738
1739 /**
1740 * Thread state for a terminated thread.
1741 * The thread has completed execution.
1742 */
1743 TERMINATED;
1744 }
1745
1746 /**
1747 * Returns the state of this thread.
1748 * This method is designed for use in monitoring of the system state,
1749 * not for synchronization control.
1750 *
1751 * @return this thread's state.
1752 * @since 1.5
1753 */
1754 public State getState() {
1755 // get current thread state
1756 return sun.misc.VM.toThreadState(threadStatus);
1757 }
1758
1759 // Added in JSR-166
1760
1761 /**
1762 * Interface for handlers invoked when a <tt>Thread</tt> abruptly
1763 * terminates due to an uncaught exception.
1764 * <p>When a thread is about to terminate due to an uncaught exception
1765 * the Java Virtual Machine will query the thread for its
1766 * <tt>UncaughtExceptionHandler</tt> using
1767 * {@link #getUncaughtExceptionHandler} and will invoke the handler's
1768 * <tt>uncaughtException</tt> method, passing the thread and the
1769 * exception as arguments.
1770 * If a thread has not had its <tt>UncaughtExceptionHandler</tt>
1771 * explicitly set, then its <tt>ThreadGroup</tt> object acts as its
1772 * <tt>UncaughtExceptionHandler</tt>. If the <tt>ThreadGroup</tt> object
1773 * has no
1774 * special requirements for dealing with the exception, it can forward
1775 * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler
1776 * default uncaught exception handler}.
1777 *
1778 * @see #setDefaultUncaughtExceptionHandler
1779 * @see #setUncaughtExceptionHandler
1780 * @see ThreadGroup#uncaughtException
1781 * @since 1.5
1782 */
1783 public interface UncaughtExceptionHandler {
1784 /**
1785 * Method invoked when the given thread terminates due to the
1786 * given uncaught exception.
1787 * <p>Any exception thrown by this method will be ignored by the
1788 * Java Virtual Machine.
1789 * @param t the thread
1790 * @param e the exception
1791 */
1792 void uncaughtException(Thread t, Throwable e);
1793 }
1794
1795 // null unless explicitly set
1796 private volatile UncaughtExceptionHandler uncaughtExceptionHandler;
1797
1798 // null unless explicitly set
1799 private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler;
1800
1801 /**
1802 * Set the default handler invoked when a thread abruptly terminates
1803 * due to an uncaught exception, and no other handler has been defined
1804 * for that thread.
1805 *
1806 * <p>Uncaught exception handling is controlled first by the thread, then
1807 * by the thread's {@link ThreadGroup} object and finally by the default
1808 * uncaught exception handler. If the thread does not have an explicit
1809 * uncaught exception handler set, and the thread's thread group
1810 * (including parent thread groups) does not specialize its
1811 * <tt>uncaughtException</tt> method, then the default handler's
1812 * <tt>uncaughtException</tt> method will be invoked.
1813 * <p>By setting the default uncaught exception handler, an application
1814 * can change the way in which uncaught exceptions are handled (such as
1815 * logging to a specific device, or file) for those threads that would
1816 * already accept whatever "default" behavior the system
1817 * provided.
1818 *
1819 * <p>Note that the default uncaught exception handler should not usually
1820 * defer to the thread's <tt>ThreadGroup</tt> object, as that could cause
1821 * infinite recursion.
1822 *
1823 * @param eh the object to use as the default uncaught exception handler.
1824 * If <tt>null</tt> then there is no default handler.
1825 *
1826 * @throws SecurityException if a security manager is present and it
1827 * denies <tt>{@link RuntimePermission}
1828 * ("setDefaultUncaughtExceptionHandler")</tt>
1829 *
1830 * @see #setUncaughtExceptionHandler
1831 * @see #getUncaughtExceptionHandler
1832 * @see ThreadGroup#uncaughtException
1833 * @since 1.5
1834 */
1835 public static void setDefaultUncaughtExceptionHandler(
1836 UncaughtExceptionHandler eh) {
1837 SecurityManager sm = System.getSecurityManager();
1838 if (sm != null) {
1839 sm.checkPermission(new RuntimePermission(
1840 "setDefaultUncaughtExceptionHandler"));
1841 }
1842
1843 defaultUncaughtExceptionHandler = eh;
1844 }
1845
1846 /**
1847 * Returns the default handler invoked when a thread abruptly terminates
1848 * due to an uncaught exception. If the returned value is <tt>null</tt>,
1849 * there is no default.
1850 * @since 1.5
1851 * @see #setDefaultUncaughtExceptionHandler
1852 */
1853 public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler() {
1854 return defaultUncaughtExceptionHandler;
1855 }
1856
1857 /**
1858 * Returns the handler invoked when this thread abruptly terminates
1859 * due to an uncaught exception. If this thread has not had an
1860 * uncaught exception handler explicitly set then this thread's
1861 * <tt>ThreadGroup</tt> object is returned, unless this thread
1862 * has terminated, in which case <tt>null</tt> is returned.
1863 * @since 1.5
1864 */
1865 public UncaughtExceptionHandler getUncaughtExceptionHandler() {
1866 return uncaughtExceptionHandler != null ? uncaughtExceptionHandler
1867 : group;
1868 }
1869
1870 /**
1871 * Set the handler invoked when this thread abruptly terminates
1872 * due to an uncaught exception.
1873 * <p>A thread can take full control of how it responds to uncaught
1874 * exceptions by having its uncaught exception handler explicitly set.
1875 * If no such handler is set then the thread's <tt>ThreadGroup</tt>
1876 * object acts as its handler.
1877 * @param eh the object to use as this thread's uncaught exception
1878 * handler. If <tt>null</tt> then this thread has no explicit handler.
1879 * @throws SecurityException if the current thread is not allowed to
1880 * modify this thread.
1881 * @see #setDefaultUncaughtExceptionHandler
1882 * @see ThreadGroup#uncaughtException
1883 * @since 1.5
1884 */
1885 public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
1886 checkAccess();
1887 uncaughtExceptionHandler = eh;
1888 }
1889
1890 /**
1891 * Dispatch an uncaught exception to the handler. This method is
1892 * intended to be called only by the JVM.
1893 */
1894 private void dispatchUncaughtException(Throwable e) {
1895 getUncaughtExceptionHandler().uncaughtException(this , e);
1896 }
1897
1898 /* Some private helper methods */
1899 private native void setPriority0(int newPriority);
1900
1901 private native void stop0(Object o);
1902
1903 private native void suspend0();
1904
1905 private native void resume0();
1906
1907 private native void interrupt0();
1908 }
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