Thread

/* * @(#)Thread.java 1.174 08/01/23 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package java.lang; import java.security.AccessController; import java.security.AccessControlContext; import java.security.PrivilegedAction; import java.util.Map; import java.util.HashMap; import java.util.Collections; import java.util.concurrent.locks.LockSupport; import sun.misc.SoftCache; import sun.nio.ch.Interruptible; import sun.security.util.SecurityConstants; /** * A <i>thread</i> is a thread of execution in a program. The Java * Virtual Machine allows an application to have multiple threads of * execution running concurrently. * <p> * Every thread has a priority. Threads with higher priority are * executed in preference to threads with lower priority. Each thread * may or may not also be marked as a daemon. When code running in * some thread creates a new <code>Thread</code> object, the new * thread has its priority initially set equal to the priority of the * creating thread, and is a daemon thread if and only if the * creating thread is a daemon. * <p> * When a Java Virtual Machine starts up, there is usually a single * non-daemon thread (which typically calls the method named * <code>main</code> of some designated class). The Java Virtual * Machine continues to execute threads until either of the following * occurs: * <ul> * <li>The <code>exit</code> method of class <code>Runtime</code> has been * called and the security manager has permitted the exit operation * to take place. * <li>All threads that are not daemon threads have died, either by * returning from the call to the <code>run</code> method or by * throwing an exception that propagates beyond the <code>run</code> * method. * </ul> * <p> * There are two ways to create a new thread of execution. One is to * declare a class to be a subclass of <code>Thread</code>. This * subclass should override the <code>run</code> method of class * <code>Thread</code>. An instance of the subclass can then be * allocated and started. For example, a thread that computes primes * larger than a stated value could be written as follows: * <p><hr><blockquote><pre> * class PrimeThread extends Thread { * long minPrime; * PrimeThread(long minPrime) { * this.minPrime = minPrime; * } * * public void run() { * // compute primes larger than minPrime *  . . . * } * } * </pre></blockquote><hr> * <p> * The following code would then create a thread and start it running: * <p><blockquote><pre> * PrimeThread p = new PrimeThread(143); * p.start(); * </pre></blockquote> * <p> * The other way to create a thread is to declare a class that * implements the <code>Runnable</code> interface. That class then * implements the <code>run</code> method. An instance of the class can * then be allocated, passed as an argument when creating * <code>Thread</code>, and started. The same example in this other * style looks like the following: * <p><hr><blockquote><pre> * class PrimeRun implements Runnable { * long minPrime; * PrimeRun(long minPrime) { * this.minPrime = minPrime; * } * * public void run() { * // compute primes larger than minPrime *  . . . * } * } * </pre></blockquote><hr> * <p> * The following code would then create a thread and start it running: * <p><blockquote><pre> * PrimeRun p = new PrimeRun(143); * new Thread(p).start(); * </pre></blockquote> * <p> * Every thread has a name for identification purposes. More than * one thread may have the same name. If a name is not specified when * a thread is created, a new name is generated for it. * * @author unascribed * @version 1.174, 01/23/08 * @see Runnable * @see Runtime#exit(int) * @see #run() * @see #stop() * @since JDK1.0 */ public class Thread implements Runnable { /* Make sure registerNatives is the first thing <clinit> does. */ private static native void registerNatives(); static { registerNatives(); } private char name[]; private int priority; private Thread threadQ; private long eetop; /* Whether or not to single_step this thread. */ private boolean single_step; /* Whether or not the thread is a daemon thread. */ private boolean daemon = false; /* JVM state */ private boolean stillborn = false; /* What will be run. */ private Runnable target; /* The group of this thread */ private ThreadGroup group; /* The context ClassLoader for this thread */ private ClassLoader contextClassLoader; /* The inherited AccessControlContext of this thread */ private AccessControlContext inheritedAccessControlContext; /* For autonumbering anonymous threads. */ private static int threadInitNumber; private static synchronized int nextThreadNum() { return threadInitNumber++; } /* ThreadLocal values pertaining to this thread. This map is maintained * by the ThreadLocal class. */ ThreadLocal.ThreadLocalMap threadLocals = null; /* * InheritableThreadLocal values pertaining to this thread. This map is * maintained by the InheritableThreadLocal class. */ ThreadLocal.ThreadLocalMap inheritableThreadLocals = null; /* * The requested stack size for this thread, or 0 if the creator did * not specify a stack size. It is up to the VM to do whatever it * likes with this number; some VMs will ignore it. */ private long stackSize; /* * JVM-private state that persists after native thread termination. */ private long nativeParkEventPointer; /* * Thread ID */ private long tid; /* For generating thread ID */ private static long threadSeqNumber; /* Java thread status for tools, * initialized to indicate thread 'not yet started' */ private int threadStatus = 0; private static synchronized long nextThreadID() { return ++threadSeqNumber; } /** * The argument supplied to the current call to * java.util.concurrent.locks.LockSupport.park. * Set by (private) java.util.concurrent.locks.LockSupport.setBlocker * Accessed using java.util.concurrent.locks.LockSupport.getBlocker */ volatile Object parkBlocker; /* The object in which this thread is blocked in an interruptible I/O * operation, if any. The blocker's interrupt method should be invoked * after setting this thread's interrupt status. */ private volatile Interruptible blocker; private Object blockerLock = new Object(); /* Set the blocker field; invoked via sun.misc.SharedSecrets from java.nio code */ void blockedOn(Interruptible b) { synchronized (blockerLock) { blocker = b; } } /** * The minimum priority that a thread can have. */ public final static int MIN_PRIORITY = 1; /** * The default priority that is assigned to a thread. */ public final static int NORM_PRIORITY = 5; /** * The maximum priority that a thread can have. */ public final static int MAX_PRIORITY = 10; /* If stop was called before start */ private boolean stopBeforeStart; /* Remembered Throwable from stop before start */ private Throwable throwableFromStop; /** * Returns a reference to the currently executing thread object. * * @return the currently executing thread. */ public static native Thread currentThread(); /** * Causes the currently executing thread object to temporarily pause * and allow other threads to execute. */ public static native void yield(); /** * Causes the currently executing thread to sleep (temporarily cease * execution) for the specified number of milliseconds, subject to * the precision and accuracy of system timers and schedulers. The thread * does not lose ownership of any monitors. * * @param millis the length of time to sleep in milliseconds. * @exception InterruptedException if any thread has interrupted * the current thread. The <i>interrupted status</i> of the * current thread is cleared when this exception is thrown. * @see Object#notify() */ public static native void sleep(long millis) throws InterruptedException; /** * Causes the currently executing thread to sleep (cease execution) * for the specified number of milliseconds plus the specified number * of nanoseconds, subject to the precision and accuracy of system * timers and schedulers. The thread does not lose ownership of any * monitors. * * @param millis the length of time to sleep in milliseconds. * @param nanos 0-999999 additional nanoseconds to sleep. * @exception IllegalArgumentException if the value of millis is * negative or the value of nanos is not in the range * 0-999999. * @exception InterruptedException if any thread has interrupted * the current thread. The <i>interrupted status</i> of the * current thread is cleared when this exception is thrown. * @see Object#notify() */ public static void sleep(long millis, int nanos) throws InterruptedException { if (millis < 0) { throw new IllegalArgumentException("timeout value is negative"); } if (nanos < 0 || nanos > 999999) { throw new IllegalArgumentException( "nanosecond timeout value out of range"); } if (nanos >= 500000 || (nanos != 0 && millis == 0)) { millis++; } sleep(millis); } /** * Initializes a Thread. * * @param g the Thread group * @param target the object whose run() method gets called * @param name the name of the new Thread * @param stackSize the desired stack size for the new thread, or * zero to indicate that this parameter is to be ignored. */ private void init(ThreadGroup g, Runnable target, String name, long stackSize) { Thread parent = currentThread(); SecurityManager security = System.getSecurityManager(); if (g == null) { /* Determine if it's an applet or not */ /* If there is a security manager, ask the security manager what to do. */ if (security != null) { g = security.getThreadGroup(); } /* If the security doesn't have a strong opinion of the matter use the parent thread group. */ if (g == null) { g = parent.getThreadGroup(); } } /* checkAccess regardless of whether or not threadgroup is explicitly passed in. */ g.checkAccess(); /* * Do we have the required permissions? */ if (security != null) { if (isCCLOverridden(getClass())) { security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION); } } g.addUnstarted(); this.group = g; this.daemon = parent.isDaemon(); this.priority = parent.getPriority(); this.name = name.toCharArray(); if (security == null || isCCLOverridden(parent.getClass())) this.contextClassLoader = parent.getContextClassLoader(); else this.contextClassLoader = parent.contextClassLoader; this.inheritedAccessControlContext = AccessController.getContext(); this.target = target; setPriority(priority); if (parent.inheritableThreadLocals != null) this.inheritableThreadLocals = ThreadLocal.createInheritedMap(parent.inheritableThreadLocals); /* Stash the specified stack size in case the VM cares */ this.stackSize = stackSize; /* Set thread ID */ tid = nextThreadID(); } /** * Allocates a new <code>Thread</code> object. This constructor has * the same effect as <code>Thread(null, null,</code> * <i>gname</i><code>)</code>, where <b><i>gname</i></b> is * a newly generated name. Automatically generated names are of the * form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer. * * @see #Thread(ThreadGroup, Runnable, String) */ public Thread() { init(null, null, "Thread-" + nextThreadNum(), 0); } /** * Allocates a new <code>Thread</code> object. This constructor has * the same effect as <code>Thread(null, target,</code> * <i>gname</i><code>)</code>, where <i>gname</i> is * a newly generated name. Automatically generated names are of the * form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer. * * @param target the object whose <code>run</code> method is called. * @see #Thread(ThreadGroup, Runnable, String) */ public Thread(Runnable target) { init(null, target, "Thread-" + nextThreadNum(), 0); } /** * Allocates a new <code>Thread</code> object. This constructor has * the same effect as <code>Thread(group, target,</code> * <i>gname</i><code>)</code>, where <i>gname</i> is * a newly generated name. Automatically generated names are of the * form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer. * * @param group the thread group. * @param target the object whose <code>run</code> method is called. * @exception SecurityException if the current thread cannot create a * thread in the specified thread group. * @see #Thread(ThreadGroup, Runnable, String) */ public Thread(ThreadGroup group, Runnable target) { init(group, target, "Thread-" + nextThreadNum(), 0); } /** * Allocates a new <code>Thread</code> object. This constructor has * the same effect as <code>Thread(null, null, name)</code>. * * @param name the name of the new thread. * @see #Thread(ThreadGroup, Runnable, String) */ public Thread(String name) { init(null, null, name, 0); } /** * Allocates a new <code>Thread</code> object. This constructor has * the same effect as <code>Thread(group, null, name)</code> * * @param group the thread group. * @param name the name of the new thread. * @exception SecurityException if the current thread cannot create a * thread in the specified thread group. * @see #Thread(ThreadGroup, Runnable, String) */ public Thread(ThreadGroup group, String name) { init(group, null, name, 0); } /** * Allocates a new <code>Thread</code> object. This constructor has * the same effect as <code>Thread(null, target, name)</code>. * * @param target the object whose <code>run</code> method is called. * @param name the name of the new thread. * @see #Thread(ThreadGroup, Runnable, String) */ public Thread(Runnable target, String name) { init(null, target, name, 0); } /** * Allocates a new <code>Thread</code> object so that it has * <code>target</code> as its run object, has the specified * <code>name</code> as its name, and belongs to the thread group * referred to by <code>group</code>. * <p> * If <code>group</code> is <code>null</code> and there is a * security manager, the group is determined by the security manager's * <code>getThreadGroup</code> method. If <code>group</code> is * <code>null</code> and there is not a security manager, or the * security manager's <code>getThreadGroup</code> method returns * <code>null</code>, the group is set to be the same ThreadGroup * as the thread that is creating the new thread. * * <p>If there is a security manager, its <code>checkAccess</code> * method is called with the ThreadGroup as its argument. * <p>In addition, its <code>checkPermission</code> * method is called with the * <code>RuntimePermission("enableContextClassLoaderOverride")</code> * permission when invoked directly or indirectly by the constructor * of a subclass which overrides the <code>getContextClassLoader</code> * or <code>setContextClassLoader</code> methods. * This may result in a SecurityException. * <p> * If the <code>target</code> argument is not <code>null</code>, the * <code>run</code> method of the <code>target</code> is called when * this thread is started. If the target argument is * <code>null</code>, this thread's <code>run</code> method is called * when this thread is started. * <p> * The priority of the newly created thread is set equal to the * priority of the thread creating it, that is, the currently running * thread. The method <code>setPriority</code> may be used to * change the priority to a new value. * <p> * The newly created thread is initially marked as being a daemon * thread if and only if the thread creating it is currently marked * as a daemon thread. The method <code>setDaemon </code> may be used * to change whether or not a thread is a daemon. * * @param group the thread group. * @param target the object whose <code>run</code> method is called. * @param name the name of the new thread. * @exception SecurityException if the current thread cannot create a * thread in the specified thread group or cannot * override the context class loader methods. * @see Runnable#run() * @see #run() * @see #setDaemon(boolean) * @see #setPriority(int) * @see ThreadGroup#checkAccess() * @see SecurityManager#checkAccess */ public Thread(ThreadGroup group, Runnable target, String name) { init(group, target, name, 0); } /** * Allocates a new <code>Thread</code> object so that it has * <code>target</code> as its run object, has the specified * <code>name</code> as its name, belongs to the thread group referred to * by <code>group</code>, and has the specified <i>stack size</i>. * * <p>This constructor is identical to {@link * #Thread(ThreadGroup,Runnable,String)} with the exception of the fact * that it allows the thread stack size to be specified. The stack size * is the approximate number of bytes of address space that the virtual * machine is to allocate for this thread's stack. <b>The effect of the * <tt>stackSize</tt> parameter, if any, is highly platform dependent.</b> * * <p>On some platforms, specifying a higher value for the * <tt>stackSize</tt> parameter may allow a thread to achieve greater * recursion depth before throwing a {@link StackOverflowError}. * Similarly, specifying a lower value may allow a greater number of * threads to exist concurrently without throwing an {@link * OutOfMemoryError} (or other internal error). The details of * the relationship between the value of the <tt>stackSize</tt> parameter * and the maximum recursion depth and concurrency level are * platform-dependent. <b>On some platforms, the value of the * <tt>stackSize</tt> parameter may have no effect whatsoever.</b> * * <p>The virtual machine is free to treat the <tt>stackSize</tt> * parameter as a suggestion. If the specified value is unreasonably low * for the platform, the virtual machine may instead use some * platform-specific minimum value; if the specified value is unreasonably * high, the virtual machine may instead use some platform-specific * maximum. Likewise, the virtual machine is free to round the specified * value up or down as it sees fit (or to ignore it completely). * * <p>Specifying a value of zero for the <tt>stackSize</tt> parameter will * cause this constructor to behave exactly like the * <tt>Thread(ThreadGroup, Runnable, String)</tt> constructor. * * <p><i>Due to the platform-dependent nature of the behavior of this * constructor, extreme care should be exercised in its use. * The thread stack size necessary to perform a given computation will * likely vary from one JRE implementation to another. In light of this * variation, careful tuning of the stack size parameter may be required, * and the tuning may need to be repeated for each JRE implementation on * which an application is to run.</i> * * <p>Implementation note: Java platform implementers are encouraged to * document their implementation's behavior with respect to the * <tt>stackSize parameter</tt>. * * @param group the thread group. * @param target the object whose <code>run</code> method is called. * @param name the name of the new thread. * @param stackSize the desired stack size for the new thread, or * zero to indicate that this parameter is to be ignored. * @exception SecurityException if the current thread cannot create a * thread in the specified thread group. * @since 1.4 */ public Thread(ThreadGroup group, Runnable target, String name, long stackSize) { init(group, target, name, stackSize); } /** * Causes this thread to begin execution; the Java Virtual Machine * calls the <code>run</code> method of this thread. * <p> * The result is that two threads are running concurrently: the * current thread (which returns from the call to the * <code>start</code> method) and the other thread (which executes its * <code>run</code> method). * <p> * It is never legal to start a thread more than once. * In particular, a thread may not be restarted once it has completed * execution. * * @exception IllegalThreadStateException if the thread was already * started. * @see #run() * @see #stop() */ public synchronized void start() { /** * This method is not invoked for the main method thread or "system" * group threads created/set up by the VM. Any new functionality added * to this method in the future may have to also be added to the VM. * * A zero status value corresponds to state "NEW". */ if (threadStatus != 0) throw new IllegalThreadStateException(); group.add(this); start0(); if (stopBeforeStart) { stop0(throwableFromStop); } } private native void start0(); /** * If this thread was constructed using a separate * <code>Runnable</code> run object, then that * <code>Runnable</code> object's <code>run</code> method is called; * otherwise, this method does nothing and returns. * <p> * Subclasses of <code>Thread</code> should override this method. * * @see #start() * @see #stop() * @see #Thread(ThreadGroup, Runnable, String) */ public void run() { if (target != null) { target.run(); } } /** * This method is called by the system to give a Thread * a chance to clean up before it actually exits. */ private void exit() { if (group != null) { group.remove(this); group = null; } /* Aggressively null out all reference fields: see bug 4006245 */ target = null; /* Speed the release of some of these resources */ threadLocals = null; inheritableThreadLocals = null; inheritedAccessControlContext = null; blocker = null; uncaughtExceptionHandler = null; } /** * Forces the thread to stop executing. * <p> * If there is a security manager installed, its <code>checkAccess</code> * method is called with <code>this</code> * as its argument. This may result in a * <code>SecurityException</code> being raised (in the current thread). * <p> * If this thread is different from the current thread (that is, the current * thread is trying to stop a thread other than itself), the * security manager's <code>checkPermission</code> method (with a * <code>RuntimePermission("stopThread")</code> argument) is called in * addition. * Again, this may result in throwing a * <code>SecurityException</code> (in the current thread). * <p> * The thread represented by this thread is forced to stop whatever * it is doing abnormally and to throw a newly created * <code>ThreadDeath</code> object as an exception. * <p> * It is permitted to stop a thread that has not yet been started. * If the thread is eventually started, it immediately terminates. * <p> * An application should not normally try to catch * <code>ThreadDeath</code> unless it must do some extraordinary * cleanup operation (note that the throwing of * <code>ThreadDeath</code> causes <code>finally</code> clauses of * <code>try</code> statements to be executed before the thread * officially dies). If a <code>catch</code> clause catches a * <code>ThreadDeath</code> object, it is important to rethrow the * object so that the thread actually dies. * <p> * The top-level error handler that reacts to otherwise uncaught * exceptions does not print out a message or otherwise notify the * application if the uncaught exception is an instance of * <code>ThreadDeath</code>. * * @exception SecurityException if the current thread cannot * modify this thread. * @see #interrupt() * @see #checkAccess() * @see #run() * @see #start() * @see ThreadDeath * @see ThreadGroup#uncaughtException(Thread,Throwable) * @see SecurityManager#checkAccess(Thread) * @see SecurityManager#checkPermission * @deprecated This method is inherently unsafe. Stopping a thread with * Thread.stop causes it to unlock all of the monitors that it * has locked (as a natural consequence of the unchecked * <code>ThreadDeath</code> exception propagating up the stack). If * any of the objects previously protected by these monitors were in * an inconsistent state, the damaged objects become visible to * other threads, potentially resulting in arbitrary behavior. Many * uses of <code>stop</code> should be replaced by code that simply * modifies some variable to indicate that the target thread should * stop running. The target thread should check this variable * regularly, and return from its run method in an orderly fashion * if the variable indicates that it is to stop running. If the * target thread waits for long periods (on a condition variable, * for example), the <code>interrupt</code> method should be used to * interrupt the wait. * For more information, see * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html" mce_href="technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. */ @Deprecated public final void stop() { // If the thread is already dead, return. // A zero status value corresponds to "NEW". if ((threadStatus != 0) && !isAlive()) { return; } stop1(new ThreadDeath()); } /** * Forces the thread to stop executing. * <p> * If there is a security manager installed, the <code>checkAccess</code> * method of this thread is called, which may result in a * <code>SecurityException</code> being raised (in the current thread). * <p> * If this thread is different from the current thread (that is, the current * thread is trying to stop a thread other than itself) or * <code>obj</code> is not an instance of <code>ThreadDeath</code>, the * security manager's <code>checkPermission</code> method (with the * <code>RuntimePermission("stopThread")</code> argument) is called in * addition. * Again, this may result in throwing a * <code>SecurityException</code> (in the current thread). * <p> * If the argument <code>obj</code> is null, a * <code>NullPointerException</code> is thrown (in the current thread). * <p> * The thread represented by this thread is forced to stop * whatever it is doing abnormally and to throw the * <code>Throwable</code> object <code>obj</code> as an exception. This * is an unusual action to take; normally, the <code>stop</code> method * that takes no arguments should be used. * <p> * It is permitted to stop a thread that has not yet been started. * If the thread is eventually started, it immediately terminates. * * @param obj the Throwable object to be thrown. * @exception SecurityException if the current thread cannot modify * this thread. * @throws NullPointerException if obj is <tt>null</tt>. * @see #interrupt() * @see #checkAccess() * @see #run() * @see #start() * @see #stop() * @see SecurityManager#checkAccess(Thread) * @see SecurityManager#checkPermission * @deprecated This method is inherently unsafe. See {@link #stop()} * for details. An additional danger of this * method is that it may be used to generate exceptions that the * target thread is unprepared to handle (including checked * exceptions that the thread could not possibly throw, were it * not for this method). * For more information, see * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html" mce_href="technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. */ @Deprecated public final synchronized void stop(Throwable obj) { stop1(obj); } /** * Common impl for stop() and stop(Throwable). */ private final synchronized void stop1(Throwable th) { SecurityManager security = System.getSecurityManager(); if (security != null) { checkAccess(); if ((this != Thread.currentThread()) || (!(th instanceof ThreadDeath))) { security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION); } } // A zero status value corresponds to "NEW" if (threadStatus != 0) { resume(); // Wake up thread if it was suspended; no-op otherwise stop0(th); } else { // Must do the null arg check that the VM would do with stop0 if (th == null) { throw new NullPointerException(); } // Remember this stop attempt for if/when start is used stopBeforeStart = true; throwableFromStop = th; } } /** * Interrupts this thread. * * <p> Unless the current thread is interrupting itself, which is * always permitted, the {@link #checkAccess() checkAccess} method * of this thread is invoked, which may cause a {@link * SecurityException} to be thrown. * * <p> If this thread is blocked in an invocation of the {@link * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link * Object#wait(long, int) wait(long, int)} methods of the {@link Object} * class, or of the {@link #join()}, {@link #join(long)}, {@link * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)}, * methods of this class, then its interrupt status will be cleared and it * will receive an {@link InterruptedException}. * * <p> If this thread is blocked in an I/O operation upon an {@link * java.nio.channels.InterruptibleChannel </code>interruptible * channel<code>} then the channel will be closed, the thread's interrupt * status will be set, and the thread will receive a {@link * java.nio.channels.ClosedByInterruptException}. * * <p> If this thread is blocked in a {@link java.nio.channels.Selector} * then the thread's interrupt status will be set and it will return * immediately from the selection operation, possibly with a non-zero * value, just as if the selector's {@link * java.nio.channels.Selector#wakeup wakeup} method were invoked. * * <p> If none of the previous conditions hold then this thread's interrupt * status will be set. </p> * * <p> Interrupting a thread that is not alive need not have any effect. * * @throws SecurityException * if the current thread cannot modify this thread * * @revised 6.0 * @spec JSR-51 */ public void interrupt() { if (this != Thread.currentThread()) checkAccess(); synchronized (blockerLock) { Interruptible b = blocker; if (b != null) { interrupt0(); // Just to set the interrupt flag b.interrupt(); return; } } interrupt0(); } /** * Tests whether the current thread has been interrupted. The * <i>interrupted status</i> of the thread is cleared by this method. In * other words, if this method were to be called twice in succession, the * second call would return false (unless the current thread were * interrupted again, after the first call had cleared its interrupted * status and before the second call had examined it). * * <p>A thread interruption ignored because a thread was not alive * at the time of the interrupt will be reflected by this method * returning false. * * @return <code>true</code> if the current thread has been interrupted; * <code>false</code> otherwise. * @see #isInterrupted() * @revised 6.0 */ public static boolean interrupted() { return currentThread().isInterrupted(true); } /** * Tests whether this thread has been interrupted. The <i>interrupted * status</i> of the thread is unaffected by this method. * * <p>A thread interruption ignored because a thread was not alive * at the time of the interrupt will be reflected by this method * returning false. * * @return <code>true</code> if this thread has been interrupted; * <code>false</code> otherwise. * @see #interrupted() * @revised 6.0 */ public boolean isInterrupted() { return isInterrupted(false); } /** * Tests if some Thread has been interrupted. The interrupted state * is reset or not based on the value of ClearInterrupted that is * passed. */ private native boolean isInterrupted(boolean ClearInterrupted); /** * Throws {@link NoSuchMethodError}. * * @deprecated This method was originally designed to destroy this * thread without any cleanup. Any monitors it held would have * remained locked. However, the method was never implemented. * If if were to be implemented, it would be deadlock-prone in * much the manner of {@link #suspend}. If the target thread held * a lock protecting a critical system resource when it was * destroyed, no thread could ever access this resource again. * If another thread ever attempted to lock this resource, deadlock * would result. Such deadlocks typically manifest themselves as * "frozen" processes. For more information, see * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html" mce_href="technotes/guides/concurrency/threadPrimitiveDeprecation.html"> * Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. * @throws NoSuchMethodError always */ @Deprecated public void destroy() { throw new NoSuchMethodError(); } /** * Tests if this thread is alive. A thread is alive if it has * been started and has not yet died. * * @return <code>true</code> if this thread is alive; * <code>false</code> otherwise. */ public final native boolean isAlive(); /** * Suspends this thread. * <p> * First, the <code>checkAccess</code> method of this thread is called * with no arguments. This may result in throwing a * <code>SecurityException </code>(in the current thread). * <p> * If the thread is alive, it is suspended and makes no further * progress unless and until it is resumed. * * @exception SecurityException if the current thread cannot modify * this thread. * @see #checkAccess * @deprecated This method has been deprecated, as it is * inherently deadlock-prone. If the target thread holds a lock on the * monitor protecting a critical system resource when it is suspended, no * thread can access this resource until the target thread is resumed. If * the thread that would resume the target thread attempts to lock this * monitor prior to calling <code>resume</code>, deadlock results. Such * deadlocks typically manifest themselves as "frozen" processes. * For more information, see * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html" mce_href="technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. */ @Deprecated public final void suspend() { checkAccess(); suspend0(); } /** * Resumes a suspended thread. * <p> * First, the <code>checkAccess</code> method of this thread is called * with no arguments. This may result in throwing a * <code>SecurityException</code> (in the current thread). * <p> * If the thread is alive but suspended, it is resumed and is * permitted to make progress in its execution. * * @exception SecurityException if the current thread cannot modify this * thread. * @see #checkAccess * @see #suspend() * @deprecated This method exists solely for use with {@link #suspend}, * which has been deprecated because it is deadlock-prone. * For more information, see * <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html" mce_href="technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why * are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>. */ @Deprecated public final void resume() { checkAccess(); resume0(); } /** * Changes the priority of this thread. * <p> * First the <code>checkAccess</code> method of this thread is called * with no arguments. This may result in throwing a * <code>SecurityException</code>. * <p> * Otherwise, the priority of this thread is set to the smaller of * the specified <code>newPriority</code> and the maximum permitted * priority of the thread's thread group. * * @param newPriority priority to set this thread to * @exception IllegalArgumentException If the priority is not in the * range <code>MIN_PRIORITY</code> to * <code>MAX_PRIORITY</code>. * @exception SecurityException if the current thread cannot modify * this thread. * @see #getPriority * @see #checkAccess() * @see #getThreadGroup() * @see #MAX_PRIORITY * @see #MIN_PRIORITY * @see ThreadGroup#getMaxPriority() */ public final void setPriority(int newPriority) { ThreadGroup g; checkAccess(); if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) { throw new IllegalArgumentException(); } if((g = getThreadGroup()) != null) { if (newPriority > g.getMaxPriority()) { newPriority = g.getMaxPriority(); } setPriority0(priority = newPriority); } } /** * Returns this thread's priority. * * @return this thread's priority. * @see #setPriority */ public final int getPriority() { return priority; } /** * Changes the name of this thread to be equal to the argument * <code>name</code>. * <p> * First the <code>checkAccess</code> method of this thread is called * with no arguments. This may result in throwing a * <code>SecurityException</code>. * * @param name the new name for this thread. * @exception SecurityException if the current thread cannot modify this * thread. * @see #getName * @see #checkAccess() */ public final void setName(String name) { checkAccess(); this.name = name.toCharArray(); } /** * Returns this thread's name. * * @return this thread's name. * @see #setName(String) */ public final String getName() { return String.valueOf(name); } /** * Returns the thread group to which this thread belongs. * This method returns null if this thread has died * (been stopped). * * @return this thread's thread group. */ public final ThreadGroup getThreadGroup() { return group; } /** * Returns the number of active threads in the current thread's thread * group. * * @return the number of active threads in the current thread's thread * group. */ public static int activeCount() { return currentThread().getThreadGroup().activeCount(); } /** * Copies into the specified array every active thread in * the current thread's thread group and its subgroups. This method simply * calls the <code>enumerate</code> method of the current thread's thread * group with the array argument. * <p> * First, if there is a security manager, that <code>enumerate</code> * method calls the security * manager's <code>checkAccess</code> method * with the thread group as its argument. This may result * in throwing a <code>SecurityException</code>. * * @param tarray an array of Thread objects to copy to * @return the number of threads put into the array * @exception SecurityException if a security manager exists and its * <code>checkAccess</code> method doesn't allow the operation. * @see ThreadGroup#enumerate(Thread[]) * @see SecurityManager#checkAccess(ThreadGroup) */ public static int enumerate(Thread tarray[]) { return currentThread().getThreadGroup().enumerate(tarray); } /** * Counts the number of stack frames in this thread. The thread must * be suspended. * * @return the number of stack frames in this thread. * @exception IllegalThreadStateException if this thread is not * suspended. * @deprecated The definition of this call depends on {@link #suspend}, * which is deprecated. Further, the results of this call * were never well-defined. */ @Deprecated public native int countStackFrames(); /** * Waits at most <code>millis</code> milliseconds for this thread to * die. A timeout of <code>0</code> means to wait forever. * * @param millis the time to wait in milliseconds. * @exception InterruptedException if any thread has interrupted * the current thread. The <i>interrupted status</i> of the * current thread is cleared when this exception is thrown. */ public final synchronized void join(long millis) throws InterruptedException { long base = System.currentTimeMillis(); long now = 0; if (millis < 0) { throw new IllegalArgumentException("timeout value is negative"); } if (millis == 0) { while (isAlive()) { wait(0); } } else { while (isAlive()) { long delay = millis - now; if (delay <= 0) { break; } wait(delay); now = System.currentTimeMillis() - base; } } } /** * Waits at most <code>millis</code> milliseconds plus * <code>nanos</code> nanoseconds for this thread to die. * * @param millis the time to wait in milliseconds. * @param nanos 0-999999 additional nanoseconds to wait. * @exception IllegalArgumentException if the value of millis is negative * the value of nanos is not in the range 0-999999. * @exception InterruptedException if any thread has interrupted * the current thread. The <i>interrupted status</i> of the * current thread is cleared when this exception is thrown. */ public final synchronized void join(long millis, int nanos) throws InterruptedException { if (millis < 0) { throw new IllegalArgumentException("timeout value is negative"); } if (nanos < 0 || nanos > 999999) { throw new IllegalArgumentException( "nanosecond timeout value out of range"); } if (nanos >= 500000 || (nanos != 0 && millis == 0)) { millis++; } join(millis); } /** * Waits for this thread to die. * * @exception InterruptedException if any thread has interrupted * the current thread. The <i>interrupted status</i> of the * current thread is cleared when this exception is thrown. */ public final void join() throws InterruptedException { join(0); } /** * Prints a stack trace of the current thread to the standard error stream. * This method is used only for debugging. * * @see Throwable#printStackTrace() */ public static void dumpStack() { new Exception("Stack trace").printStackTrace(); } /** * Marks this thread as either a daemon thread or a user thread. The * Java Virtual Machine exits when the only threads running are all * daemon threads. * <p> * This method must be called before the thread is started. * <p> * This method first calls the <code>checkAccess</code> method * of this thread * with no arguments. This may result in throwing a * <code>SecurityException </code>(in the current thread). * * @param on if <code>true</code>, marks this thread as a * daemon thread. * @exception IllegalThreadStateException if this thread is active. * @exception SecurityException if the current thread cannot modify * this thread. * @see #isDaemon() * @see #checkAccess */ public final void setDaemon(boolean on) { checkAccess(); if (isAlive()) { throw new IllegalThreadStateException(); } daemon = on; } /** * Tests if this thread is a daemon thread. * * @return <code>true</code> if this thread is a daemon thread; * <code>false</code> otherwise. * @see #setDaemon(boolean) */ public final boolean isDaemon() { return daemon; } /** * Determines if the currently running thread has permission to * modify this thread. * <p> * If there is a security manager, its <code>checkAccess</code> method * is called with this thread as its argument. This may result in * throwing a <code>SecurityException</code>. * * @exception SecurityException if the current thread is not allowed to * access this thread. * @see SecurityManager#checkAccess(Thread) */ public final void checkAccess() { SecurityManager security = System.getSecurityManager(); if (security != null) { security.checkAccess(this); } } /** * Returns a string representation of this thread, including the * thread's name, priority, and thread group. * * @return a string representation of this thread. */ public String toString() { ThreadGroup group = getThreadGroup(); if (group != null) { return "Thread[" + getName() + "," + getPriority() + "," + group.getName() + "]"; } else { return "Thread[" + getName() + "," + getPriority() + "," + "" + "]"; } } /** * Returns the context ClassLoader for this Thread. The context * ClassLoader is provided by the creator of the thread for use * by code running in this thread when loading classes and resources. * If not set, the default is the ClassLoader context of the parent * Thread. The context ClassLoader of the primordial thread is * typically set to the class loader used to load the application. * * <p>First, if there is a security manager, and the caller's class * loader is not null and the caller's class loader is not the same as or * an ancestor of the context class loader for the thread whose * context class loader is being requested, then the security manager's * <code>checkPermission</code> * method is called with a * <code>RuntimePermission("getClassLoader")</code> permission * to see if it's ok to get the context ClassLoader.. * * @return the context ClassLoader for this Thread * * @throws SecurityException * if a security manager exists and its * <code>checkPermission</code> method doesn't allow * getting the context ClassLoader. * @see #setContextClassLoader * @see SecurityManager#checkPermission * @see RuntimePermission * * @since 1.2 */ public ClassLoader getContextClassLoader() { if (contextClassLoader == null) return null; SecurityManager sm = System.getSecurityManager(); if (sm != null) { ClassLoader ccl = ClassLoader.getCallerClassLoader(); if (ccl != null && ccl != contextClassLoader && !contextClassLoader.isAncestor(ccl)) { sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION); } } return contextClassLoader; } /** * Sets the context ClassLoader for this Thread. The context * ClassLoader can be set when a thread is created, and allows * the creator of the thread to provide the appropriate class loader * to code running in the thread when loading classes and resources. * * <p>First, if there is a security manager, its <code>checkPermission</code> * method is called with a * <code>RuntimePermission("setContextClassLoader")</code> permission * to see if it's ok to set the context ClassLoader.. * * @param cl the context ClassLoader for this Thread * * @exception SecurityException if the current thread cannot set the * context ClassLoader. * @see #getContextClassLoader * @see SecurityManager#checkPermission * @see RuntimePermission * * @since 1.2 */ public void setContextClassLoader(ClassLoader cl) { SecurityManager sm = System.getSecurityManager(); if (sm != null) { sm.checkPermission(new RuntimePermission("setContextClassLoader")); } contextClassLoader = cl; } /** * Returns <tt>true</tt> if and only if the current thread holds the * monitor lock on the specified object. * * <p>This method is designed to allow a program to assert that * the current thread already holds a specified lock: * <pre> * assert Thread.holdsLock(obj); * </pre> * * @param obj the object on which to test lock ownership * @throws NullPointerException if obj is <tt>null</tt> * @return <tt>true</tt> if the current thread holds the monitor lock on * the specified object. * @since 1.4 */ public static native boolean holdsLock(Object obj); private static final StackTraceElement[] EMPTY_STACK_TRACE = new StackTraceElement[0]; /** * Returns an array of stack trace elements representing the stack dump * of this thread. This method will return a zero-length array if * this thread has not started or has terminated. * If the returned array is of non-zero length then the first element of * the array represents the top of the stack, which is the most recent * method invocation in the sequence. The last element of the array * represents the bottom of the stack, which is the least recent method * invocation in the sequence. * * <p>If there is a security manager, and this thread is not * the current thread, then the security manager's * <tt>checkPermission</tt> method is called with a * <tt>RuntimePermission("getStackTrace")</tt> permission * to see if it's ok to get the stack trace. * * <p>Some virtual machines may, under some circumstances, omit one * or more stack frames from the stack trace. In the extreme case, * a virtual machine that has no stack trace information concerning * this thread is permitted to return a zero-length array from this * method. * * @return an array of <tt>StackTraceElement</tt>, * each represents one stack frame. * * @throws SecurityException * if a security manager exists and its * <tt>checkPermission</tt> method doesn't allow * getting the stack trace of thread. * @see SecurityManager#checkPermission * @see RuntimePermission * @see Throwable#getStackTrace * * @since 1.5 */ public StackTraceElement[] getStackTrace() { if (this != Thread.currentThread()) { // check for getStackTrace permission SecurityManager security = System.getSecurityManager(); if (security != null) { security.checkPermission( SecurityConstants.GET_STACK_TRACE_PERMISSION); } // optimization so we do not call into the vm for threads that // have not yet started or have terminated if (!isAlive()) { return EMPTY_STACK_TRACE; } StackTraceElement[][] stackTraceArray = dumpThreads(new Thread[] {this}); StackTraceElement[] stackTrace = stackTraceArray[0]; // a thread that was alive during the previous isAlive call may have // since terminated, therefore not having a stacktrace. if (stackTrace == null) { stackTrace = EMPTY_STACK_TRACE; } return stackTrace; } else { // Don't need JVM help for current thread return (new Exception()).getStackTrace(); } } /** * Returns a map of stack traces for all live threads. * The map keys are threads and each map value is an array of * <tt>StackTraceElement</tt> that represents the stack dump * of the corresponding <tt>Thread</tt>. * The returned stack traces are in the format specified for * the {@link #getStackTrace getStackTrace} method. * * <p>The threads may be executing while this method is called. * The stack trace of each thread only represents a snapshot and * each stack trace may be obtained at different time. A zero-length * array will be returned in the map value if the virtual machine has * no stack trace information about a thread. * * <p>If there is a security manager, then the security manager's * <tt>checkPermission</tt> method is called with a * <tt>RuntimePermission("getStackTrace")</tt> permission as well as * <tt>RuntimePermission("modifyThreadGroup")</tt> permission * to see if it is ok to get the stack trace of all threads. * * @return a <tt>Map</tt> from <tt>Thread</tt> to an array of * <tt>StackTraceElement</tt> that represents the stack trace of * the corresponding thread. * * @throws SecurityException * if a security manager exists and its * <tt>checkPermission</tt> method doesn't allow * getting the stack trace of thread. * @see #getStackTrace * @see SecurityManager#checkPermission * @see RuntimePermission * @see Throwable#getStackTrace * * @since 1.5 */ public static Map<Thread, StackTraceElement[]> getAllStackTraces() { // check for getStackTrace permission SecurityManager security = System.getSecurityManager(); if (security != null) { security.checkPermission( SecurityConstants.GET_STACK_TRACE_PERMISSION); security.checkPermission( SecurityConstants.MODIFY_THREADGROUP_PERMISSION); } // Get a snapshot of the list of all threads Thread[] threads = getThreads(); StackTraceElement[][] traces = dumpThreads(threads); Map<Thread, StackTraceElement[]> m = new HashMap<Thread, StackTraceElement[]>(threads.length); for (int i = 0; i < threads.length; i++) { StackTraceElement[] stackTrace = traces[i]; if (stackTrace != null) { m.put(threads[i], stackTrace); } // else terminated so we don't put it in the map } return m; } private static final RuntimePermission SUBCLASS_IMPLEMENTATION_PERMISSION = new RuntimePermission("enableContextClassLoaderOverride"); /** cache of subclass security audit results */ private static final SoftCache subclassAudits = new SoftCache(10); /** * Verifies that this (possibly subclass) instance can be constructed * without violating security constraints: the subclass must not override * security-sensitive non-final methods, or else the * "enableContextClassLoaderOverride" RuntimePermission is checked. */ private static boolean isCCLOverridden(Class cl) { if (cl == Thread.class) return false; Boolean result = null; synchronized (subclassAudits) { result = (Boolean) subclassAudits.get(cl); if (result == null) { /* * Note: only new Boolean instances (i.e., not Boolean.TRUE or * Boolean.FALSE) must be used as cache values, otherwise cache * entry will pin associated class. */ result = new Boolean(auditSubclass(cl)); subclassAudits.put(cl, result); } } return result.booleanValue(); } /** * Performs reflective checks on given subclass to verify that it doesn't * override security-sensitive non-final methods. Returns true if the * subclass overrides any of the methods, false otherwise. */ private static boolean auditSubclass(final Class subcl) { Boolean result = (Boolean) AccessController.doPrivileged( new PrivilegedAction() { public Object run() { for (Class cl = subcl; cl != Thread.class; cl = cl.getSuperclass()) { try { cl.getDeclaredMethod("getContextClassLoader", new Class[0]); return Boolean.TRUE; } catch (NoSuchMethodException ex) { } try { Class[] params = {ClassLoader.class}; cl.getDeclaredMethod("setContextClassLoader", params); return Boolean.TRUE; } catch (NoSuchMethodException ex) { } } return Boolean.FALSE; } } ); return result.booleanValue(); } private native static StackTraceElement[][] dumpThreads(Thread[] threads); private native static Thread[] getThreads(); /** * Returns the identifier of this Thread. The thread ID is a positive * <tt>long</tt> number generated when this thread was created. * The thread ID is unique and remains unchanged during its lifetime. * When a thread is terminated, this thread ID may be reused. * * @return this thread's ID. * @since 1.5 */ public long getId() { return tid; } /** * A thread state. A thread can be in one of the following states: * <ul> * <li>{@link #NEW}<br> * A thread that has not yet started is in this state. * </li> * <li>{@link #RUNNABLE}<br> * A thread executing in the Java virtual machine is in this state. * </li> * <li>{@link #BLOCKED}<br> * A thread that is blocked waiting for a monitor lock * is in this state. * </li> * <li>{@link #WAITING}<br> * A thread that is waiting indefinitely for another thread to * perform a particular action is in this state. * </li> * <li>{@link #TIMED_WAITING}<br> * A thread that is waiting for another thread to perform an action * for up to a specified waiting time is in this state. * </li> * <li>{@link #TERMINATED}<br> * A thread that has exited is in this state. * </li> * </ul> * * <p> * A thread can be in only one state at a given point in time. * These states are virtual machine states which do not reflect * any operating system thread states. * * @since 1.5 * @see #getState */ public enum State { /** * Thread state for a thread which has not yet started. */ NEW, /** * Thread state for a runnable thread. A thread in the runnable * state is executing in the Java virtual machine but it may * be waiting for other resources from the operating system * such as processor. */ RUNNABLE, /** * Thread state for a thread blocked waiting for a monitor lock. * A thread in the blocked state is waiting for a monitor lock * to enter a synchronized block/method or * reenter a synchronized block/method after calling * {@link Object#wait() Object.wait}. */ BLOCKED, /** * Thread state for a waiting thread. * A thread is in the waiting state due to calling one of the * following methods: * <ul> * <li>{@link Object#wait() Object.wait} with no timeout</li> * <li>{@link #join() Thread.join} with no timeout</li> * <li>{@link LockSupport#park() LockSupport.park}</li> * </ul> * * <p>A thread in the waiting state is waiting for another thread to * perform a particular action. * * For example, a thread that has called <tt>Object.wait()</tt> * on an object is waiting for another thread to call * <tt>Object.notify()</tt> or <tt>Object.notifyAll()</tt> on * that object. A thread that has called <tt>Thread.join()</tt> * is waiting for a specified thread to terminate. */ WAITING, /** * Thread state for a waiting thread with a specified waiting time. * A thread is in the timed waiting state due to calling one of * the following methods with a specified positive waiting time: * <ul> * <li>{@link #sleep Thread.sleep}</li> * <li>{@link Object#wait(long) Object.wait} with timeout</li> * <li>{@link #join(long) Thread.join} with timeout</li> * <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li> * <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li> * </ul> */ TIMED_WAITING, /** * Thread state for a terminated thread. * The thread has completed execution. */ TERMINATED; } /** * Returns the state of this thread. * This method is designed for use in monitoring of the system state, * not for synchronization control. * * @return this thread's state. * @since 1.5 */ public State getState() { // get current thread state return sun.misc.VM.toThreadState(threadStatus); } // Added in JSR-166 /** * Interface for handlers invoked when a <tt>Thread</tt> abruptly * terminates due to an uncaught exception. * <p>When a thread is about to terminate due to an uncaught exception * the Java Virtual Machine will query the thread for its * <tt>UncaughtExceptionHandler</tt> using * {@link #getUncaughtExceptionHandler} and will invoke the handler's * <tt>uncaughtException</tt> method, passing the thread and the * exception as arguments. * If a thread has not had its <tt>UncaughtExceptionHandler</tt> * explicitly set, then its <tt>ThreadGroup</tt> object acts as its * <tt>UncaughtExceptionHandler</tt>. If the <tt>ThreadGroup</tt> object * has no * special requirements for dealing with the exception, it can forward * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler * default uncaught exception handler}. * * @see #setDefaultUncaughtExceptionHandler * @see #setUncaughtExceptionHandler * @see ThreadGroup#uncaughtException * @since 1.5 */ public interface UncaughtExceptionHandler { /** * Method invoked when the given thread terminates due to the * given uncaught exception. * <p>Any exception thrown by this method will be ignored by the * Java Virtual Machine. * @param t the thread * @param e the exception */ void uncaughtException(Thread t, Throwable e); } // null unless explicitly set private volatile UncaughtExceptionHandler uncaughtExceptionHandler; // null unless explicitly set private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler; /** * Set the default handler invoked when a thread abruptly terminates * due to an uncaught exception, and no other handler has been defined * for that thread. * * <p>Uncaught exception handling is controlled first by the thread, then * by the thread's {@link ThreadGroup} object and finally by the default * uncaught exception handler. If the thread does not have an explicit * uncaught exception handler set, and the thread's thread group * (including parent thread groups) does not specialize its * <tt>uncaughtException</tt> method, then the default handler's * <tt>uncaughtException</tt> method will be invoked. * <p>By setting the default uncaught exception handler, an application * can change the way in which uncaught exceptions are handled (such as * logging to a specific device, or file) for those threads that would * already accept whatever "default" behavior the system * provided. * * <p>Note that the default uncaught exception handler should not usually * defer to the thread's <tt>ThreadGroup</tt> object, as that could cause * infinite recursion. * * @param eh the object to use as the default uncaught exception handler. * If <tt>null</tt> then there is no default handler. * * @throws SecurityException if a security manager is present and it * denies <tt>{@link RuntimePermission} * ("setDefaultUncaughtExceptionHandler")</tt> * * @see #setUncaughtExceptionHandler * @see #getUncaughtExceptionHandler * @see ThreadGroup#uncaughtException * @since 1.5 */ public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler eh) { SecurityManager sm = System.getSecurityManager(); if (sm != null) { sm.checkPermission( new RuntimePermission("setDefaultUncaughtExceptionHandler") ); } defaultUncaughtExceptionHandler = eh; } /** * Returns the default handler invoked when a thread abruptly terminates * due to an uncaught exception. If the returned value is <tt>null</tt>, * there is no default. * @since 1.5 * @see #setDefaultUncaughtExceptionHandler */ public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler(){ return defaultUncaughtExceptionHandler; } /** * Returns the handler invoked when this thread abruptly terminates * due to an uncaught exception. If this thread has not had an * uncaught exception handler explicitly set then this thread's * <tt>ThreadGroup</tt> object is returned, unless this thread * has terminated, in which case <tt>null</tt> is returned. * @since 1.5 */ public UncaughtExceptionHandler getUncaughtExceptionHandler() { return uncaughtExceptionHandler != null ? uncaughtExceptionHandler : group; } /** * Set the handler invoked when this thread abruptly terminates * due to an uncaught exception. * <p>A thread can take full control of how it responds to uncaught * exceptions by having its uncaught exception handler explicitly set. * If no such handler is set then the thread's <tt>ThreadGroup</tt> * object acts as its handler. * @param eh the object to use as this thread's uncaught exception * handler. If <tt>null</tt> then this thread has no explicit handler. * @throws SecurityException if the current thread is not allowed to * modify this thread. * @see #setDefaultUncaughtExceptionHandler * @see ThreadGroup#uncaughtException * @since 1.5 */ public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh) { checkAccess(); uncaughtExceptionHandler = eh; } /** * Dispatch an uncaught exception to the handler. This method is * intended to be called only by the JVM. */ private void dispatchUncaughtException(Throwable e) { getUncaughtExceptionHandler().uncaughtException(this, e); } /* Some private helper methods */ private native void setPriority0(int newPriority); private native void stop0(Object o); private native void suspend0(); private native void resume0(); private native void interrupt0(); }