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Thread.javaAPI DocJava SE 6 API69931Tue Jun 10 00:25:36 BST 2008java.lang

Thread

public class Thread extends Object implements Runnable
A thread is a thread of execution in a program. The Java Virtual Machine allows an application to have multiple threads of execution running concurrently.

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 Thread 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.

When a Java Virtual Machine starts up, there is usually a single non-daemon thread (which typically calls the method named main of some designated class). The Java Virtual Machine continues to execute threads until either of the following occurs:

  • The exit method of class Runtime has been called and the security manager has permitted the exit operation to take place.
  • All threads that are not daemon threads have died, either by returning from the call to the run method or by throwing an exception that propagates beyond the run method.

There are two ways to create a new thread of execution. One is to declare a class to be a subclass of Thread. This subclass should override the run method of class Thread. 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:


class PrimeThread extends Thread {
long minPrime;
PrimeThread(long minPrime) {
this.minPrime = minPrime;
}

public void run() {
// compute primes larger than minPrime
 . . .
}
}

The following code would then create a thread and start it running:

PrimeThread p = new PrimeThread(143);
p.start();

The other way to create a thread is to declare a class that implements the Runnable interface. That class then implements the run method. An instance of the class can then be allocated, passed as an argument when creating Thread, and started. The same example in this other style looks like the following:


class PrimeRun implements Runnable {
long minPrime;
PrimeRun(long minPrime) {
this.minPrime = minPrime;
}

public void run() {
// compute primes larger than minPrime
 . . .
}
}

The following code would then create a thread and start it running:

PrimeRun p = new PrimeRun(143);
new Thread(p).start();

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
1.173, 07/13/06
see
Runnable
see
Runtime#exit(int)
see
#run()
see
#stop()
since
JDK1.0

Fields Summary
private char[]
name
private int
priority
private Thread
threadQ
private long
eetop
private boolean
single_step
private boolean
daemon
private boolean
stillborn
private Runnable
target
private ThreadGroup
group
private ClassLoader
contextClassLoader
private AccessControlContext
inheritedAccessControlContext
private static int
threadInitNumber
ThreadLocal$ThreadLocalMap
threadLocals
ThreadLocal$ThreadLocalMap
inheritableThreadLocals
private long
stackSize
private long
nativeParkEventPointer
private long
tid
private static long
threadSeqNumber
private int
threadStatus
volatile Object
parkBlocker
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
private volatile Interruptible
blocker
private Object
blockerLock
public static final int
MIN_PRIORITY
The minimum priority that a thread can have.
public static final int
NORM_PRIORITY
The default priority that is assigned to a thread.
public static final int
MAX_PRIORITY
The maximum priority that a thread can have.
private boolean
stopBeforeStart
private Throwable
throwableFromStop
private static final StackTraceElement[]
EMPTY_STACK_TRACE
private static final RuntimePermission
SUBCLASS_IMPLEMENTATION_PERMISSION
private static final SoftCache
subclassAudits
cache of subclass security audit results
private volatile UncaughtExceptionHandler
uncaughtExceptionHandler
private static volatile UncaughtExceptionHandler
defaultUncaughtExceptionHandler
Constructors Summary
public Thread()
Allocates a new Thread object. This constructor has the same effect as Thread(null, null, gname), where gname is a newly generated name. Automatically generated names are of the form "Thread-"+n, where n is an integer.

see
#Thread(ThreadGroup, Runnable, String)

	init(null, null, "Thread-" + nextThreadNum(), 0);
    
public Thread(Runnable target)
Allocates a new Thread object. This constructor has the same effect as Thread(null, target, gname), where gname is a newly generated name. Automatically generated names are of the form "Thread-"+n, where n is an integer.

param
target the object whose run method is called.
see
#Thread(ThreadGroup, Runnable, String)

	init(null, target, "Thread-" + nextThreadNum(), 0);
    
public Thread(ThreadGroup group, Runnable target)
Allocates a new Thread object. This constructor has the same effect as Thread(group, target, gname), where gname is a newly generated name. Automatically generated names are of the form "Thread-"+n, where n is an integer.

param
group the thread group.
param
target the object whose run method is called.
exception
SecurityException if the current thread cannot create a thread in the specified thread group.
see
#Thread(ThreadGroup, Runnable, String)

	init(group, target, "Thread-" + nextThreadNum(), 0);
    
public Thread(String name)
Allocates a new Thread object. This constructor has the same effect as Thread(null, null, name).

param
name the name of the new thread.
see
#Thread(ThreadGroup, Runnable, String)

	init(null, null, name, 0);
    
public Thread(ThreadGroup group, String name)
Allocates a new Thread object. This constructor has the same effect as Thread(group, null, name)

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)

	init(group, null, name, 0);
    
public Thread(Runnable target, String name)
Allocates a new Thread object. This constructor has the same effect as Thread(null, target, name).

param
target the object whose run method is called.
param
name the name of the new thread.
see
#Thread(ThreadGroup, Runnable, String)

	init(null, target, name, 0);
    
public Thread(ThreadGroup group, Runnable target, String name)
Allocates a new Thread object so that it has target as its run object, has the specified name as its name, and belongs to the thread group referred to by group.

If group is null and there is a security manager, the group is determined by the security manager's getThreadGroup method. If group is null and there is not a security manager, or the security manager's getThreadGroup method returns null, the group is set to be the same ThreadGroup as the thread that is creating the new thread.

If there is a security manager, its checkAccess method is called with the ThreadGroup as its argument.

In addition, its checkPermission method is called with the RuntimePermission("enableContextClassLoaderOverride") permission when invoked directly or indirectly by the constructor of a subclass which overrides the getContextClassLoader or setContextClassLoader methods. This may result in a SecurityException.

If the target argument is not null, the run method of the target is called when this thread is started. If the target argument is null, this thread's run method is called when this thread is started.

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 setPriority may be used to change the priority to a new value.

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 setDaemon may be used to change whether or not a thread is a daemon.

param
group the thread group.
param
target the object whose run 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

	init(group, target, name, 0);
    
public Thread(ThreadGroup group, Runnable target, String name, long stackSize)
Allocates a new Thread object so that it has target as its run object, has the specified name as its name, belongs to the thread group referred to by group, and has the specified stack size.

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. The effect of the stackSize parameter, if any, is highly platform dependent.

On some platforms, specifying a higher value for the stackSize 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 stackSize parameter and the maximum recursion depth and concurrency level are platform-dependent. On some platforms, the value of the stackSize parameter may have no effect whatsoever.

The virtual machine is free to treat the stackSize 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).

Specifying a value of zero for the stackSize parameter will cause this constructor to behave exactly like the Thread(ThreadGroup, Runnable, String) constructor.

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.

Implementation note: Java platform implementers are encouraged to document their implementation's behavior with respect to the stackSize parameter.

param
group the thread group.
param
target the object whose run 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

	init(group, target, name, stackSize);
    
Methods Summary
public static intactiveCount()
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.

	return currentThread().getThreadGroup().activeCount();
    
private static booleanauditSubclass(java.lang.Class subcl)
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.

	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();
    
voidblockedOn(sun.nio.ch.Interruptible b)


    /* Set the blocker field; invoked via sun.misc.SharedSecrets from java.nio code
     */
       
	synchronized (blockerLock) {
	    blocker = b;
	}
    
public final voidcheckAccess()
Determines if the currently running thread has permission to modify this thread.

If there is a security manager, its checkAccess method is called with this thread as its argument. This may result in throwing a SecurityException.

exception
SecurityException if the current thread is not allowed to access this thread.
see
SecurityManager#checkAccess(Thread)

	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkAccess(this);
	}
    
public native intcountStackFrames()
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.

public static native java.lang.ThreadcurrentThread()
Returns a reference to the currently executing thread object.

return
the currently executing thread.

public voiddestroy()
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 Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?.
throws
NoSuchMethodError always

	throw new NoSuchMethodError();
    
private voiddispatchUncaughtException(java.lang.Throwable e)
Dispatch an uncaught exception to the handler. This method is intended to be called only by the JVM.

        getUncaughtExceptionHandler().uncaughtException(this, e);
    
public static voiddumpStack()
Prints a stack trace of the current thread to the standard error stream. This method is used only for debugging.

see
Throwable#printStackTrace()

	new Exception("Stack trace").printStackTrace();
    
private static native java.lang.StackTraceElement[][]dumpThreads(java.lang.Thread[] threads)

public static intenumerate(java.lang.Thread[] tarray)
Copies into the specified array every active thread in the current thread's thread group and its subgroups. This method simply calls the enumerate method of the current thread's thread group with the array argument.

First, if there is a security manager, that enumerate method calls the security manager's checkAccess method with the thread group as its argument. This may result in throwing a SecurityException.

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 checkAccess method doesn't allow the operation.
see
ThreadGroup#enumerate(Thread[])
see
SecurityManager#checkAccess(ThreadGroup)

	return currentThread().getThreadGroup().enumerate(tarray);
    
private voidexit()
This method is called by the system to give a Thread a chance to clean up before it actually exits.

	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;
    
public static java.util.MapgetAllStackTraces()
Returns a map of stack traces for all live threads. The map keys are threads and each map value is an array of StackTraceElement that represents the stack dump of the corresponding Thread. The returned stack traces are in the format specified for the {@link #getStackTrace getStackTrace} method.

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.

If there is a security manager, then the security manager's checkPermission method is called with a RuntimePermission("getStackTrace") permission as well as RuntimePermission("modifyThreadGroup") permission to see if it is ok to get the stack trace of all threads.

return
a Map from Thread to an array of StackTraceElement that represents the stack trace of the corresponding thread.
throws
SecurityException if a security manager exists and its checkPermission method doesn't allow getting the stack trace of thread.
see
#getStackTrace
see
SecurityManager#checkPermission
see
RuntimePermission
see
Throwable#getStackTrace
since
1.5

        // 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++) {
            if (threads[i].isAlive()) { 
                StackTraceElement[] stackTrace = traces[i];
                if (stackTrace == null) {
                    stackTrace = EMPTY_STACK_TRACE;
                } 
                m.put(threads[i], stackTrace);
            }
        }
        return m;
    
public java.lang.ClassLoadergetContextClassLoader()
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.

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 checkPermission method is called with a RuntimePermission("getClassLoader") 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 checkPermission method doesn't allow getting the context ClassLoader.
see
#setContextClassLoader
see
SecurityManager#checkPermission
see
RuntimePermission
since
1.2

	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;
    
public static java.lang.Thread$UncaughtExceptionHandlergetDefaultUncaughtExceptionHandler()
Returns the default handler invoked when a thread abruptly terminates due to an uncaught exception. If the returned value is null, there is no default.

since
1.5
see
#setDefaultUncaughtExceptionHandler

        return defaultUncaughtExceptionHandler;
    
public longgetId()
Returns the identifier of this Thread. The thread ID is a positive long 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

        return tid;
    
public final java.lang.StringgetName()
Returns this thread's name.

return
this thread's name.
see
#setName(String)

	return String.valueOf(name);
    
public final intgetPriority()
Returns this thread's priority.

return
this thread's priority.
see
#setPriority

	return priority;
    
public java.lang.StackTraceElement[]getStackTrace()
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.

If there is a security manager, and this thread is not the current thread, then the security manager's checkPermission method is called with a RuntimePermission("getStackTrace") permission to see if it's ok to get the stack trace.

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 StackTraceElement, each represents one stack frame.
throws
SecurityException if a security manager exists and its checkPermission method doesn't allow getting the stack trace of thread.
see
SecurityManager#checkPermission
see
RuntimePermission
see
Throwable#getStackTrace
since
1.5


                                                                                                                                                                                                                                                   
       
        if (this != Thread.currentThread()) {
            // check for getStackTrace permission
            SecurityManager security = System.getSecurityManager();
            if (security != null) {
                security.checkPermission(
                    SecurityConstants.GET_STACK_TRACE_PERMISSION);
            }
	    if (!isAlive()) {
		return EMPTY_STACK_TRACE;
	    }
	    return dumpThreads(new Thread[] {this})[0];
        } else {
	    // Don't need JVM help for current thread
	    return (new Exception()).getStackTrace();
	}
    
public java.lang.Thread$StategetState()
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

        // get current thread state
        return sun.misc.VM.toThreadState(threadStatus);
    
public final java.lang.ThreadGroupgetThreadGroup()
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.

	return group;
    
private static native java.lang.Thread[]getThreads()

public java.lang.Thread$UncaughtExceptionHandlergetUncaughtExceptionHandler()
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 ThreadGroup object is returned, unless this thread has terminated, in which case null is returned.

since
1.5

 
        return uncaughtExceptionHandler != null ?
            uncaughtExceptionHandler : group;
    
public static native booleanholdsLock(java.lang.Object obj)
Returns true if and only if the current thread holds the monitor lock on the specified object.

This method is designed to allow a program to assert that the current thread already holds a specified lock:

assert Thread.holdsLock(obj);

param
obj the object on which to test lock ownership
throws
NullPointerException if obj is null
return
true if the current thread holds the monitor lock on the specified object.
since
1.4

private voidinit(java.lang.ThreadGroup g, java.lang.Runnable target, java.lang.String name, long stackSize)
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.

	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();
    
public voidinterrupt()
Interrupts this thread.

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.

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}.

If this thread is blocked in an I/O operation upon an {@link java.nio.channels.InterruptibleChannel interruptible channel} 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}.

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.

If none of the previous conditions hold then this thread's interrupt status will be set.

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

	if (this != Thread.currentThread())
	    checkAccess();

	synchronized (blockerLock) {
	    Interruptible b = blocker;
	    if (b != null) {
		interrupt0();		// Just to set the interrupt flag
		b.interrupt();
		return;
	    }
	}
	interrupt0();
    
private native voidinterrupt0()

public static booleaninterrupted()
Tests whether the current thread has been interrupted. The interrupted status 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).

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
true if the current thread has been interrupted; false otherwise.
see
#isInterrupted()
revised
6.0

	return currentThread().isInterrupted(true);
    
public final native booleanisAlive()
Tests if this thread is alive. A thread is alive if it has been started and has not yet died.

return
true if this thread is alive; false otherwise.

private static booleanisCCLOverridden(java.lang.Class cl)
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.



                                     
         
	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();
    
public final booleanisDaemon()
Tests if this thread is a daemon thread.

return
true if this thread is a daemon thread; false otherwise.
see
#setDaemon(boolean)

	return daemon;
    
public booleanisInterrupted()
Tests whether this thread has been interrupted. The interrupted status of the thread is unaffected by this method.

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
true if this thread has been interrupted; false otherwise.
see
#interrupted()
revised
6.0

	return isInterrupted(false);
    
private native booleanisInterrupted(boolean ClearInterrupted)
Tests if some Thread has been interrupted. The interrupted state is reset or not based on the value of ClearInterrupted that is passed.

public final synchronized voidjoin(long millis)
Waits at most millis milliseconds for this thread to die. A timeout of 0 means to wait forever.

param
millis the time to wait in milliseconds.
exception
InterruptedException if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.

	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;
	    }
	}
    
public final synchronized voidjoin(long millis, int nanos)
Waits at most millis milliseconds plus nanos 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 interrupted status of the current thread is cleared when this exception is thrown.


	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);
    
public final voidjoin()
Waits for this thread to die.

exception
InterruptedException if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.

	join(0);
    
private static synchronized longnextThreadID()



         
	return ++threadSeqNumber;
    
private static synchronized intnextThreadNum()

         
	return threadInitNumber++;
    
private static native voidregisterNatives()

public final voidresume()
Resumes a suspended thread.

First, the checkAccess method of this thread is called with no arguments. This may result in throwing a SecurityException (in the current thread).

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 Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?.

	checkAccess();
	resume0();
    
private native voidresume0()

public voidrun()
If this thread was constructed using a separate Runnable run object, then that Runnable object's run method is called; otherwise, this method does nothing and returns.

Subclasses of Thread should override this method.

see
#start()
see
#stop()
see
#Thread(ThreadGroup, Runnable, String)

	if (target != null) {
	    target.run();
	}
    
public voidsetContextClassLoader(java.lang.ClassLoader cl)
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.

First, if there is a security manager, its checkPermission method is called with a RuntimePermission("setContextClassLoader") 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

	SecurityManager sm = System.getSecurityManager();
	if (sm != null) {
	    sm.checkPermission(new RuntimePermission("setContextClassLoader"));
	}
	contextClassLoader = cl;
    
public final voidsetDaemon(boolean on)
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.

This method must be called before the thread is started.

This method first calls the checkAccess method of this thread with no arguments. This may result in throwing a SecurityException (in the current thread).

param
on if true, 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

	checkAccess();
	if (isAlive()) {
	    throw new IllegalThreadStateException();
	}
	daemon = on;
    
public static voidsetDefaultUncaughtExceptionHandler(java.lang.Thread$UncaughtExceptionHandler eh)
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.

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 uncaughtException method, then the default handler's uncaughtException method will be invoked.

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.

Note that the default uncaught exception handler should not usually defer to the thread's ThreadGroup object, as that could cause infinite recursion.

param
eh the object to use as the default uncaught exception handler. If null then there is no default handler.
throws
SecurityException if a security manager is present and it denies {@link RuntimePermission} ("setDefaultUncaughtExceptionHandler")
see
#setUncaughtExceptionHandler
see
#getUncaughtExceptionHandler
see
ThreadGroup#uncaughtException
since
1.5

        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(
                new RuntimePermission("setDefaultUncaughtExceptionHandler")
                    );
        }

         defaultUncaughtExceptionHandler = eh;
     
public final voidsetName(java.lang.String name)
Changes the name of this thread to be equal to the argument name.

First the checkAccess method of this thread is called with no arguments. This may result in throwing a SecurityException.

param
name the new name for this thread.
exception
SecurityException if the current thread cannot modify this thread.
see
#getName
see
#checkAccess()

	checkAccess();
	this.name = name.toCharArray();
    
public final voidsetPriority(int newPriority)
Changes the priority of this thread.

First the checkAccess method of this thread is called with no arguments. This may result in throwing a SecurityException.

Otherwise, the priority of this thread is set to the smaller of the specified newPriority 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 MIN_PRIORITY to MAX_PRIORITY.
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()

        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);
        }
    
private native voidsetPriority0(int newPriority)

public voidsetUncaughtExceptionHandler(java.lang.Thread$UncaughtExceptionHandler eh)
Set the handler invoked when this thread abruptly terminates due to an uncaught exception.

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 ThreadGroup object acts as its handler.

param
eh the object to use as this thread's uncaught exception handler. If null 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

 
        checkAccess();
        uncaughtExceptionHandler = eh;
    
public static native voidsleep(long millis)
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 interrupted status of the current thread is cleared when this exception is thrown.
see
Object#notify()

public static voidsleep(long millis, int nanos)
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 interrupted status of the current thread is cleared when this exception is thrown.
see
Object#notify()


                        
        

                          
        

    	                                                                                                                        
           

                                                                                                                                                                                                 
           
      
	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);
    
public synchronized voidstart()
Causes this thread to begin execution; the Java Virtual Machine calls the run method of this thread.

The result is that two threads are running concurrently: the current thread (which returns from the call to the start method) and the other thread (which executes its run method).

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()

        /**
	 * 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 voidstart0()

public final voidstop()
Forces the thread to stop executing.

If there is a security manager installed, its checkAccess method is called with this as its argument. This may result in a SecurityException being raised (in the current thread).

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 checkPermission method (with a RuntimePermission("stopThread") argument) is called in addition. Again, this may result in throwing a SecurityException (in the current thread).

The thread represented by this thread is forced to stop whatever it is doing abnormally and to throw a newly created ThreadDeath object as an exception.

It is permitted to stop a thread that has not yet been started. If the thread is eventually started, it immediately terminates.

An application should not normally try to catch ThreadDeath unless it must do some extraordinary cleanup operation (note that the throwing of ThreadDeath causes finally clauses of try statements to be executed before the thread officially dies). If a catch clause catches a ThreadDeath object, it is important to rethrow the object so that the thread actually dies.

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 ThreadDeath.

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 ThreadDeath 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 stop 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 interrupt method should be used to interrupt the wait. For more information, see Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?.

        // If the thread is already dead, return.
	// A zero status value corresponds to "NEW".
	if ((threadStatus != 0) && !isAlive()) {
	    return;
	}
	stop1(new ThreadDeath());
    
public final synchronized voidstop(java.lang.Throwable obj)
Forces the thread to stop executing.

If there is a security manager installed, the checkAccess method of this thread is called, which may result in a SecurityException being raised (in the current thread).

If this thread is different from the current thread (that is, the current thread is trying to stop a thread other than itself) or obj is not an instance of ThreadDeath, the security manager's checkPermission method (with the RuntimePermission("stopThread") argument) is called in addition. Again, this may result in throwing a SecurityException (in the current thread).

If the argument obj is null, a NullPointerException is thrown (in the current thread).

The thread represented by this thread is forced to stop whatever it is doing abnormally and to throw the Throwable object obj as an exception. This is an unusual action to take; normally, the stop method that takes no arguments should be used.

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 null.
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 Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?.

	stop1(obj);
    
private native voidstop0(java.lang.Object o)

private final synchronized voidstop1(java.lang.Throwable th)
Common impl for stop() and stop(Throwable).

	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;
        }
    
public final voidsuspend()
Suspends this thread.

First, the checkAccess method of this thread is called with no arguments. This may result in throwing a SecurityException (in the current thread).

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 resume, deadlock results. Such deadlocks typically manifest themselves as "frozen" processes. For more information, see Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?.

	checkAccess();
	suspend0();
    
private native voidsuspend0()

public java.lang.StringtoString()
Returns a string representation of this thread, including the thread's name, priority, and thread group.

return
a string representation of this thread.

        ThreadGroup group = getThreadGroup();
	if (group != null) {
	    return "Thread[" + getName() + "," + getPriority() + "," + 
		           group.getName() + "]";
	} else {
	    return "Thread[" + getName() + "," + getPriority() + "," + 
		            "" + "]";
	}
    
public static native voidyield()
Causes the currently executing thread object to temporarily pause and allow other threads to execute.