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java.lang
public class: Thread [javadoc | source]
java.lang.Object
   java.lang.Thread

All Implemented Interfaces:
    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:

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.

Unless otherwise noted, passing a {@code null} argument to a constructor or method in this class will cause a NullPointerException to be thrown.

Nested Class Summary:
public enum class  Thread.State  A thread state. A thread can be in one of the following states:
  • {@link #NEW}
    A thread that has not yet started is in this state.
  • {@link #RUNNABLE}
    A thread executing in the Java virtual machine is in this state.
  • {@link #BLOCKED}
    A thread that is blocked waiting for a monitor lock is in this state.
  • {@link #WAITING}
    A thread that is waiting indefinitely for another thread to perform a particular action is in this state.
  • {@link #TIMED_WAITING}
    A thread that is waiting for another thread to perform an action for up to a specified waiting time is in this state.
  • {@link #TERMINATED}
    A thread that has exited is in this state.

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. 

public interface  Thread.UncaughtExceptionHandler  Interface for handlers invoked when a Thread abruptly terminates due to an uncaught exception.

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 #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}. 

static class  Thread.WeakClassKey  Weak key for Class objects. * 
Field Summary
 ThreadLocalMap threadLocals     
 ThreadLocalMap inheritableThreadLocals     
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 
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. 
Constructor:
 public Thread() 
 public Thread(Runnable target) 
    Allocates a new {@code Thread} object. This constructor has the same effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} {@code (null, target, gname)}, where {@code gname} is a newly generated name. Automatically generated names are of the form {@code "Thread-"+}n, where n is an integer.
    Parameters:
    target - the object whose {@code run} method is invoked when this thread is started. If {@code null}, this classes {@code run} method does nothing.
 public Thread(String name) 
    Allocates a new {@code Thread} object. This constructor has the same effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} {@code (null, null, name)}.
    Parameters:
    name - the name of the new thread
 public Thread(ThreadGroup group,
    Runnable target) 
    Allocates a new {@code Thread} object. This constructor has the same effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} {@code (group, target, gname)} ,where {@code gname} is a newly generated name. Automatically generated names are of the form {@code "Thread-"+}n, where n is an integer.
    Parameters:
    group - the thread group. If {@code null} and there is a security manager, the group is determined by {@linkplain SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. If there is not a security manager or {@code SecurityManager.getThreadGroup()} returns {@code null}, the group is set to the current thread's thread group.
    target - the object whose {@code run} method is invoked when this thread is started. If {@code null}, this thread's run method is invoked.
    Throws:
    SecurityException - if the current thread cannot create a thread in the specified thread group
 public Thread(ThreadGroup group,
    String name) 
    Allocates a new {@code Thread} object. This constructor has the same effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} {@code (group, null, name)}.
    Parameters:
    group - the thread group. If {@code null} and there is a security manager, the group is determined by {@linkplain SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. If there is not a security manager or {@code SecurityManager.getThreadGroup()} returns {@code null}, the group is set to the current thread's thread group.
    name - the name of the new thread
    Throws:
    SecurityException - if the current thread cannot create a thread in the specified thread group
 public Thread(Runnable target,
    String name) 
    Allocates a new {@code Thread} object. This constructor has the same effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread} {@code (null, target, name)}.
    Parameters:
    target - the object whose {@code run} method is invoked when this thread is started. If {@code null}, this thread's run method is invoked.
    name - the name of the new thread
 public Thread(ThreadGroup group,
    Runnable target,
    String name) 
    Allocates a new {@code Thread} object so that it has {@code target} as its run object, has the specified {@code name} as its name, and belongs to the thread group referred to by {@code group}.

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

    In addition, its {@code checkPermission} method is invoked with the {@code RuntimePermission("enableContextClassLoaderOverride")} permission when invoked directly or indirectly by the constructor of a subclass which overrides the {@code getContextClassLoader} or {@code setContextClassLoader} methods.

    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 {@linkplain #setPriority 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 {@linkplain #setDaemon setDaemon} may be used to change whether or not a thread is a daemon.

    Parameters:
    group - the thread group. If {@code null} and there is a security manager, the group is determined by {@linkplain SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. If there is not a security manager or {@code SecurityManager.getThreadGroup()} returns {@code null}, the group is set to the current thread's thread group.
    target - the object whose {@code run} method is invoked when this thread is started. If {@code null}, this thread's run method is invoked.
    name - the name of the new thread
    Throws:
    SecurityException - if the current thread cannot create a thread in the specified thread group or cannot override the context class loader methods.
 public Thread(ThreadGroup group,
    Runnable target,
    String name,
    long stackSize) 
    Allocates a new {@code Thread} object so that it has {@code target} as its run object, has the specified {@code name} as its name, and belongs to the thread group referred to by {@code group}, and has the specified stack size.

    This constructor is identical to #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 {@code stackSize} parameter, if any, is highly platform dependent.

    On some platforms, specifying a higher value for the {@code stackSize} parameter may allow a thread to achieve greater recursion depth before throwing a StackOverflowError . Similarly, specifying a lower value may allow a greater number of threads to exist concurrently without throwing an 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 {@code stackSize} parameter may have no effect whatsoever.

    The virtual machine is free to treat the {@code 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 {@code stackSize} parameter will cause this constructor to behave exactly like the {@code 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 {@code stackSize} parameter.

    Parameters:
    group - the thread group. If {@code null} and there is a security manager, the group is determined by {@linkplain SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}. If there is not a security manager or {@code SecurityManager.getThreadGroup()} returns {@code null}, the group is set to the current thread's thread group.
    target - the object whose {@code run} method is invoked when this thread is started. If {@code null}, this thread's run method is invoked.
    name - the name of the new thread
    stackSize - the desired stack size for the new thread, or zero to indicate that this parameter is to be ignored.
    Throws:
    SecurityException - if the current thread cannot create a thread in the specified thread group
    since: 1.4 -
Method from java.lang.Thread Summary:
activeCount,   blockedOn,   checkAccess,   clone,   countStackFrames,   currentThread,   destroy,   dumpStack,   enumerate,   getAllStackTraces,   getContextClassLoader,   getDefaultUncaughtExceptionHandler,   getId,   getName,   getPriority,   getStackTrace,   getState,   getThreadGroup,   getUncaughtExceptionHandler,   holdsLock,   interrupt,   interrupted,   isAlive,   isDaemon,   isInterrupted,   join,   join,   join,   processQueue,   resume,   run,   setContextClassLoader,   setDaemon,   setDefaultUncaughtExceptionHandler,   setName,   setPriority,   setUncaughtExceptionHandler,   sleep,   sleep,   start,   stop,   stop,   suspend,   toString,   yield
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from java.lang.Thread Detail:
 public static int activeCount() 
    Returns an estimate of the number of active threads in the current thread's {@linkplain java.lang.ThreadGroup thread group} and its subgroups. Recursively iterates over all subgroups in the current thread's thread group.

    The value returned is only an estimate because the number of threads may change dynamically while this method traverses internal data structures, and might be affected by the presence of certain system threads. This method is intended primarily for debugging and monitoring purposes.

  void blockedOn(Interruptible b) 
 public final  void checkAccess() 
    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.

 protected Object clone() throws CloneNotSupportedException 
    Throws CloneNotSupportedException as a Thread can not be meaningfully cloned. Construct a new Thread instead.
 public native int countStackFrames()Deprecated! The -  definition of this call depends on #suspend ,
            which is deprecated.  Further, the results of this call
            were never well-defined.

    Counts the number of stack frames in this thread. The thread must be suspended.
 public static native Thread currentThread()
    Returns a reference to the currently executing thread object.
 public  void destroy() 
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 #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?.

 public static  void dumpStack() 
    Prints a stack trace of the current thread to the standard error stream. This method is used only for debugging.
 public static int enumerate(Thread[] tarray) 
    Copies into the specified array every active thread in the current thread's thread group and its subgroups. This method simply invokes the java.lang.ThreadGroup#enumerate(Thread[]) method of the current thread's thread group.

    An application might use the {@linkplain #activeCount activeCount} method to get an estimate of how big the array should be, however if the array is too short to hold all the threads, the extra threads are silently ignored. If it is critical to obtain every active thread in the current thread's thread group and its subgroups, the invoker should verify that the returned int value is strictly less than the length of {@code tarray}.

    Due to the inherent race condition in this method, it is recommended that the method only be used for debugging and monitoring purposes.

 public static Map<Thread, StackTraceElement> getAllStackTraces() 
    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 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.

 public ClassLoader getContextClassLoader() 
    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 {@linkplain #setContextClassLoader 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.

    If a security manager is present, and the invoker's class loader is not {@code null} and is not the same as or an ancestor of the context class loader, then this method invokes the security manager's checkPermission method with a RuntimePermission {@code ("getClassLoader")} permission to verify that retrieval of the context class loader is permitted.

 public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler() 
    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.
 public long getId() 
    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.
 public final String getName() 
    Returns this thread's name.
 public final int getPriority() 
    Returns this thread's priority.
 public 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, has started but has not yet been scheduled to run by the system, 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.

 public State getState() 
    Returns the state of this thread. This method is designed for use in monitoring of the system state, not for synchronization control.
 public final ThreadGroup getThreadGroup() 
    Returns the thread group to which this thread belongs. This method returns null if this thread has died (been stopped).
 public UncaughtExceptionHandler getUncaughtExceptionHandler() 
    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.
 public static native boolean holdsLock(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);
    
 public  void interrupt() 
 public static boolean interrupted() 
    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.

 public final native boolean isAlive()
    Tests if this thread is alive. A thread is alive if it has been started and has not yet died.
 public final boolean isDaemon() 
    Tests if this thread is a daemon thread.
 public boolean isInterrupted() 
    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.

 public final  void join() throws InterruptedException 
    Waits for this thread to die.

    An invocation of this method behaves in exactly the same way as the invocation

    {@linkplain #join(long) join}{@code (0)}
 public final synchronized  void join(long millis) throws InterruptedException 
    Waits at most {@code millis} milliseconds for this thread to die. A timeout of {@code 0} means to wait forever.

    This implementation uses a loop of {@code this.wait} calls conditioned on {@code this.isAlive}. As a thread terminates the {@code this.notifyAll} method is invoked. It is recommended that applications not use {@code wait}, {@code notify}, or {@code notifyAll} on {@code Thread} instances.

 public final synchronized  void join(long millis,
    int nanos) throws InterruptedException 
    Waits at most {@code millis} milliseconds plus {@code nanos} nanoseconds for this thread to die.

    This implementation uses a loop of {@code this.wait} calls conditioned on {@code this.isAlive}. As a thread terminates the {@code this.notifyAll} method is invoked. It is recommended that applications not use {@code wait}, {@code notify}, or {@code notifyAll} on {@code Thread} instances.

 static  void processQueue(ReferenceQueue<?> queue,
    ConcurrentMap<WeakReference, ?> map) 
    Removes from the specified map any keys that have been enqueued on the specified reference queue.
 public final  void resume() 
Deprecated! This - method exists solely for use with #suspend , which has been deprecated because it is deadlock-prone. For more information, see Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?.

    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.

 public  void run() 
    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.

 public  void setContextClassLoader(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, through {@code getContextClassLoader}, to code running in the thread when loading classes and resources.

    If a security manager is present, its checkPermission method is invoked with a RuntimePermission {@code ("setContextClassLoader")} permission to see if setting the context ClassLoader is permitted.

 public final  void setDaemon(boolean on) 
    Marks this thread as either a {@linkplain #isDaemon daemon} thread or a user thread. The Java Virtual Machine exits when the only threads running are all daemon threads.

    This method must be invoked before the thread is started.

 public static  void setDefaultUncaughtExceptionHandler(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 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.

 public final  void setName(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.

 public final  void setPriority(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.

 public  void setUncaughtExceptionHandler(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.

 public static native  void sleep(long millis) throws InterruptedException
    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.
 public static  void sleep(long millis,
    int nanos) throws InterruptedException 
    Causes the currently executing thread to sleep (temporarily 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.
 public synchronized  void start() 
    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.

 public final  void stop() 
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?.

    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.

 public final synchronized  void stop(Throwable obj) 
Deprecated! This - method is inherently unsafe. See #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?.

    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.

 public final  void suspend() 
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?.

    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.

 public String toString() 
    Returns a string representation of this thread, including the thread's name, priority, and thread group.
 public static native  void yield()
    A hint to the scheduler that the current thread is willing to yield its current use of a processor. The scheduler is free to ignore this hint.

    Yield is a heuristic attempt to improve relative progression between threads that would otherwise over-utilise a CPU. Its use should be combined with detailed profiling and benchmarking to ensure that it actually has the desired effect.

    It is rarely appropriate to use this method. It may be useful for debugging or testing purposes, where it may help to reproduce bugs due to race conditions. It may also be useful when designing concurrency control constructs such as the ones in the java.util.concurrent.locks package.