* 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:
*
exit method of class Runtime has been
* called and the security manager has permitted the exit operation
* to take place.
* 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 1.155, 06/26/04
* @see java.lang.Runnable
* @see java.lang.Runtime#exit(int)
* @see java.lang.Thread#run()
* @see java.lang.Thread#stop()
* @since JDK1.0
*/
public
class Thread implements Runnable {
/* Make sure registerNatives is the first thing
* If If there is a security manager, its In addition, its
* If the
* 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
* 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 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
* The result is that two threads are running concurrently: the
* current thread (which returns from the call to the
*
* 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 java.lang.Thread#run()
* @see java.lang.Thread#stop()
*/
public synchronized void start() {
if (started)
throw new IllegalThreadStateException();
started = true;
group.add(this);
start0();
}
private native void start0();
/**
* If this thread was constructed using a separate
*
* Subclasses of
* If there is a security manager installed, its
* 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
* The thread represented by this thread is forced to stop whatever
* it is doing abnormally and to throw a newly created
*
* 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
*
* 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
*
* If there is a security manager installed, the
* If this thread is different from the current thread (that is, the current
* thread is trying to stop a thread other than itself) or
*
* If the argument
* The thread represented by this thread is forced to complete
* whatever it is doing abnormally and to throw the
*
* 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.
* @see java.lang.Thread#interrupt()
* @see java.lang.Thread#checkAccess()
* @see java.lang.Thread#run()
* @see java.lang.Thread#start()
* @see java.lang.Thread#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?.
*/
@Deprecated
public final synchronized void stop(Throwable obj) {
SecurityManager security = System.getSecurityManager();
if (security != null) {
checkAccess();
if ((this != Thread.currentThread()) ||
(!(obj instanceof ThreadDeath))) {
security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
}
}
resume(); // Wake up thread if it was suspended; no-op otherwise
stop0(obj);
}
/**
* 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 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.
* First, the
* 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
* First, the
* 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 java.lang.Thread#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?.
*/
@Deprecated
public final void resume() {
checkAccess();
resume0();
}
/**
* Changes the priority of this thread.
*
* First the
* Otherwise, the priority of this thread is set to the smaller of
* the specified
* First the
* First, if there is a security manager, that
* This method must be called before the thread is started.
*
* This method first calls the
* If there is a security manager, its
* Note: This method was mistakenly non-final in JDK 1.1.
* It has been made final in the Java 2 Platform.
*
* @exception SecurityException if the current thread is not allowed to
* access this thread.
* @see java.lang.SecurityManager#checkAccess(java.lang.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.
*
* 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
* First, if there is a security manager, its This method is designed to allow a program to assert that
* the current thread already holds a specified lock:
* 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 java.lang.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);
}
}
if (!isAlive()) {
return EMPTY_STACK_TRACE;
}
Thread[] threads = new Thread[1];
threads[0] = this;
StackTraceElement[][] result = dumpThreads(threads);
return result[0];
}
/**
* 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 java.lang.RuntimePermission
* @see Throwable#getStackTrace
*
* @since 1.5
*/
public static Map
* 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 Thread#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:
* A thread in the waiting state is waiting for another thread to
* perform a particular action.
*
* For example, a thread that has called Object.wait()
* on an object is waiting for another thread to call
* Object.notify() or Object.notifyAll() on
* that object. A thread that has called Thread.join()
* 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:
* When a thread is about to terminate due to an uncaught exception
* the Java Virtual Machine will query the thread for its
* UncaughtExceptionHandler using
* {@link Thread#getUncaughtExceptionHandler} and will invoke the handler's
* uncaughtException method, passing the thread and the
* exception as arguments.
* If a thread has not had its UncaughtExceptionHandler
* explicitly set, then its ThreadGroup object acts as its
* UncaughtExceptionHandler. If the ThreadGroup 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.
* 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.
*
* 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
*/
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 null,
* 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
* ThreadGroup object is returned, unless this thread
* has terminated, in which case null 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.
* 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
*/
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();
}
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 java.lang.Thread#Thread(java.lang.ThreadGroup,
* java.lang.Runnable, java.lang.String)
*/
public Thread() {
init(null, null, "Thread-" + nextThreadNum(), 0);
}
/**
* 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 java.lang.Thread#Thread(java.lang.ThreadGroup,
* java.lang.Runnable, java.lang.String)
*/
public Thread(Runnable target) {
init(null, target, "Thread-" + nextThreadNum(), 0);
}
/**
* 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 java.lang.Thread#Thread(java.lang.ThreadGroup,
* java.lang.Runnable, java.lang.String)
*/
public Thread(ThreadGroup group, Runnable target) {
init(group, target, "Thread-" + nextThreadNum(), 0);
}
/**
* 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 java.lang.Thread#Thread(java.lang.ThreadGroup,
* java.lang.Runnable, java.lang.String)
*/
public Thread(String name) {
init(null, null, name, 0);
}
/**
* 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 java.lang.Thread#Thread(java.lang.ThreadGroup,
* java.lang.Runnable, java.lang.String)
*/
public Thread(ThreadGroup group, String name) {
init(group, null, name, 0);
}
/**
* 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 java.lang.Thread#Thread(java.lang.ThreadGroup,
* java.lang.Runnable, java.lang.String)
*/
public Thread(Runnable target, String name) {
init(null, target, name, 0);
}
/**
* 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.
* 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.
*
* checkAccess
* method is called with the ThreadGroup as its argument.
* 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.
* 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.
* setPriority may be used to
* change the priority to a new value.
* 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 java.lang.Runnable#run()
* @see java.lang.Thread#run()
* @see java.lang.Thread#setDaemon(boolean)
* @see java.lang.Thread#setPriority(int)
* @see java.lang.ThreadGroup#checkAccess()
* @see SecurityManager#checkAccess
*/
public Thread(ThreadGroup group, Runnable target, String name) {
init(group, target, name, 0);
}
/**
* 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.
*
* 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.
*/
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 run method of this thread.
* start method) and the other thread (which executes its
* run method).
* Runnable run object, then that
* Runnable object's run method is called;
* otherwise, this method does nothing and returns.
* Thread should override this method.
*
* @see java.lang.Thread#start()
* @see java.lang.Thread#stop()
* @see java.lang.Thread#Thread(java.lang.ThreadGroup,
* java.lang.Runnable, java.lang.String)
* @see java.lang.Runnable#run()
*/
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.
* checkAccess
* method is called with this
* as its argument. This may result in a
* SecurityException being raised (in the current thread).
* checkPermission method (with a
* RuntimePermission("stopThread") argument) is called in
* addition.
* Again, this may result in throwing a
* SecurityException (in the current thread).
* ThreadDeath object as an exception.
* 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.
* ThreadDeath.
*
* @exception SecurityException if the current thread cannot
* modify this thread.
* @see java.lang.Thread#interrupt()
* @see java.lang.Thread#checkAccess()
* @see java.lang.Thread#run()
* @see java.lang.Thread#start()
* @see java.lang.ThreadDeath
* @see java.lang.ThreadGroup#uncaughtException(java.lang.Thread,
* java.lang.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?.
*/
@Deprecated
public final void stop() {
synchronized (this) {
//if the thread is already dead, return
if (!this.isAlive()) return;
SecurityManager security = System.getSecurityManager();
if (security != null) {
checkAccess();
if (this != Thread.currentThread()) {
security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
}
}
resume(); // Wake up thread if it was suspended; no-op otherwise
stop0(new ThreadDeath());
}
}
/**
* Forces the thread to stop executing.
* checkAccess
* method of this thread is called, which may result in a
* SecurityException being raised (in the current thread).
* 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).
* obj is null, a
* NullPointerException is thrown (in the current thread).
* Throwable object obj as an exception. This
* is an unusual action to take; normally, the stop method
* that takes no arguments should be used.
* } 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}.
*
* true if the current thread has been interrupted;
* false otherwise.
* @see java.lang.Thread#isInterrupted()
*/
public static boolean interrupted() {
return currentThread().isInterrupted(true);
}
/**
* Tests whether this thread has been interrupted. The interrupted
* status of the thread is unaffected by this method.
*
* @return true if this thread has been interrupted;
* false otherwise.
* @see java.lang.Thread#interrupted()
*/
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
*
* Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?.
* @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 true if this thread is alive;
* false otherwise.
*/
public final native boolean isAlive();
/**
* Suspends this thread.
* checkAccess method of this thread is called
* with no arguments. This may result in throwing a
* SecurityException (in the current thread).
* 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?.
*/
@Deprecated
public final void suspend() {
checkAccess();
suspend0();
}
/**
* Resumes a suspended thread.
* checkAccess method of this thread is called
* with no arguments. This may result in throwing a
* SecurityException (in the current thread).
* checkAccess method of this thread is called
* with no arguments. This may result in throwing a
* SecurityException.
* 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 java.lang.Thread#checkAccess()
* @see java.lang.Thread#getPriority()
* @see java.lang.Thread#getThreadGroup()
* @see java.lang.Thread#MAX_PRIORITY
* @see java.lang.Thread#MIN_PRIORITY
* @see java.lang.ThreadGroup#getMaxPriority()
*/
public final void setPriority(int newPriority) {
checkAccess();
if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
throw new IllegalArgumentException();
}
if (newPriority > group.getMaxPriority()) {
newPriority = group.getMaxPriority();
}
setPriority0(priority = newPriority);
}
/**
* Returns this thread's priority.
*
* @return this thread's priority.
* @see #setPriority
* @see java.lang.Thread#setPriority(int)
*/
public final int getPriority() {
return priority;
}
/**
* Changes the name of this thread to be equal to the argument
* name.
* 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 java.lang.Thread#checkAccess()
* @see java.lang.Thread#getName()
*/
public final void setName(String name) {
checkAccess();
this.name = name.toCharArray();
}
/**
* Returns this thread's name.
*
* @return this thread's name.
* @see #setName
* @see java.lang.Thread#setName(java.lang.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 enumerate method of the current thread's thread
* group with the array argument.
* 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 java.lang.ThreadGroup#enumerate(java.lang.Thread[])
* @see java.lang.SecurityManager#checkAccess(java.lang.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 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 another thread has interrupted
* the current thread. The interrupted status 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 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 another thread has interrupted
* the current thread. The interrupted status 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 another thread has interrupted
* the current thread. The interrupted status 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. This method is used
* only for debugging.
*
* @see java.lang.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.
* 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 java.lang.Thread#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 true if this thread is a daemon thread;
* false otherwise.
* @see java.lang.Thread#setDaemon(boolean)
*/
public final boolean isDaemon() {
return daemon;
}
/**
* Determines if the currently running thread has permission to
* modify this thread.
* checkAccess method
* is called with this thread as its argument. This may result in
* throwing a SecurityException.
* 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 java.lang.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.
*
* 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 java.lang.RuntimePermission
*
* @since 1.2
*/
public void setContextClassLoader(ClassLoader cl) {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(new RuntimePermission("setContextClassLoader"));
}
contextClassLoader = cl;
}
/**
* Returns true if and only if the current thread holds the
* monitor lock on the specified object.
*
*
* 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
*/
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.
*
*
*
*
*
* A thread that has not yet started is in this state.
*
* A thread executing in the Java virtual machine is in this state.
*
* A thread that is blocked waiting for a monitor lock
* is in this state.
*
* A thread that is waiting indefinitely for another thread to
* perform a particular action is in this state.
*
* A thread that is waiting for another thread to perform an action
* for up to a specified waiting time is in this state.
*
* A thread that has exited is in this state.
*
*
*
*
*
*/
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 Thread abruptly
* terminates due to an uncaught exception.
*