java.lang

Class ThreadGroup

java.lang.Object

java.lang.ThreadGroup

All Implemented Interfaces:

Thread.UncaughtExceptionHandler

public class ThreadGroup
extends Object
implements Thread.UncaughtExceptionHandler

ThreadGroup is a means of organizing threads into a hierarchical structure. This class is obsolete. See Effective Java Item 73, "Avoid thread groups" for details.

See Also:

Thread

Constructor Summary

Constructors

Constructor and Description
ThreadGroup(String name) Constructs a new ThreadGroup with the given name.
ThreadGroup(ThreadGroup parent, String name) Constructs a new ThreadGroup with the given name, as a child of the given ThreadGroup.

Method Summary

Modifier and Type	Method and Description
int	activeCount() Returns the number of running Threads which are children of this thread group, directly or indirectly.
int	activeGroupCount() Returns the number of ThreadGroups which are children of this group, directly or indirectly.
boolean	allowThreadSuspension(boolean b) Deprecated. Required deprecated method suspend().
void	checkAccess() Does nothing.
void	destroy() Destroys this thread group and recursively all its subgroups.
int	enumerate(Thread[] threads) Iterates over all active threads in this group (and its sub-groups) and stores the threads in the given array.
int	enumerate(Thread[] threads, boolean recurse) Iterates over all active threads in this group (and, optionally, its sub-groups) and stores the threads in the given array.
int	enumerate(ThreadGroup[] groups) Iterates over all thread groups in this group (and its sub-groups) and and stores the groups in the given array.
int	enumerate(ThreadGroup[] groups, boolean recurse) Iterates over all thread groups in this group (and, optionally, its sub-groups) and stores the groups in the given array.
int	getMaxPriority() Returns the maximum allowed priority for a Thread in this thread group.
String	getName() Returns the name of this thread group.
ThreadGroup	getParent() Returns this thread group's parent ThreadGroup.
void	interrupt() Interrupts every Thread in this group and recursively in all its subgroups.
boolean	isDaemon() Checks whether this thread group is a daemon ThreadGroup.
boolean	isDestroyed() Checks whether this thread group has already been destroyed.
void	list() Outputs to System.out a text representation of the hierarchy of Threads and ThreadGroups in this thread group (and recursively).
boolean	parentOf(ThreadGroup g) Checks whether this thread group is a direct or indirect parent group of a given ThreadGroup.
void	resume() Deprecated. Requires deprecated method Thread.resume().
void	setDaemon(boolean isDaemon) Sets whether this is a daemon ThreadGroup or not.
void	setMaxPriority(int newMax) Configures the maximum allowed priority for a Thread in this group and recursively in all its subgroups.
void	stop() Deprecated. Requires deprecated method Thread.stop().
void	suspend() Deprecated. Requires deprecated method Thread.suspend().
String	toString() Returns a string containing a concise, human-readable description of this object.
void	uncaughtException(Thread t, Throwable e) Handles uncaught exceptions.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ThreadGroup

public ThreadGroup(String name)

Constructs a new ThreadGroup with the given name. The new ThreadGroup will be child of the ThreadGroup to which the calling thread belongs.

Parameters:

name - the name

See Also:

Thread.currentThread()

ThreadGroup

public ThreadGroup(ThreadGroup parent,
                   String name)

Constructs a new ThreadGroup with the given name, as a child of the given ThreadGroup.

Parameters:

parent - the parent

name - the name

Throws:

NullPointerException - if parent == null

IllegalThreadStateException - if parent has been destroyed already

Method Detail

activeCount

public int activeCount()

Returns the number of running Threads which are children of this thread group, directly or indirectly.

Returns:

the number of children

activeGroupCount

public int activeGroupCount()

Returns the number of ThreadGroups which are children of this group, directly or indirectly.

Returns:

the number of children

allowThreadSuspension

@Deprecated
public boolean allowThreadSuspension(boolean b)

Deprecated. Required deprecated method suspend().

Does nothing. The definition of this method depends on the deprecated method suspend(). The exact behavior of this call was never specified.

Parameters:

b - Used to control low memory implicit suspension

Returns:

true (always)

checkAccess

public final void checkAccess()

Does nothing.

destroy

public final void destroy()

Destroys this thread group and recursively all its subgroups. It is only legal to destroy a ThreadGroup that has no threads in it. Any daemon ThreadGroup is destroyed automatically when it becomes empty (no threads or thread groups in it).

Throws:

IllegalThreadStateException - if this thread group or any of its subgroups has been destroyed already or if it still contains threads.

enumerate

public int enumerate(Thread[] threads)

Iterates over all active threads in this group (and its sub-groups) and stores the threads in the given array. Returns when the array is full or no more threads remain, whichever happens first.

Note that this method will silently ignore any threads that don't fit in the supplied array.

Parameters:

threads - the array into which the Threads will be copied

Returns:

the number of Threads that were copied

enumerate

public int enumerate(Thread[] threads,
                     boolean recurse)

Iterates over all active threads in this group (and, optionally, its sub-groups) and stores the threads in the given array. Returns when the array is full or no more threads remain, whichever happens first.

Note that this method will silently ignore any threads that don't fit in the supplied array.

Parameters:

threads - the array into which the Threads will be copied

recurse - indicates whether Threads in subgroups should be recursively copied as well

Returns:

the number of Threads that were copied

enumerate

public int enumerate(ThreadGroup[] groups)

Iterates over all thread groups in this group (and its sub-groups) and and stores the groups in the given array. Returns when the array is full or no more groups remain, whichever happens first.

Note that this method will silently ignore any thread groups that don't fit in the supplied array.

Parameters:

groups - the array into which the ThreadGroups will be copied

Returns:

the number of ThreadGroups that were copied

enumerate

public int enumerate(ThreadGroup[] groups,
                     boolean recurse)

Iterates over all thread groups in this group (and, optionally, its sub-groups) and stores the groups in the given array. Returns when the array is full or no more groups remain, whichever happens first.

Note that this method will silently ignore any thread groups that don't fit in the supplied array.

Parameters:

groups - the array into which the ThreadGroups will be copied

recurse - indicates whether ThreadGroups in subgroups should be recursively copied as well or not

Returns:

the number of ThreadGroups that were copied

getMaxPriority

public final int getMaxPriority()

Returns the maximum allowed priority for a Thread in this thread group.

Returns:

the maximum priority

See Also:

setMaxPriority(int)

getName

public final String getName()

Returns the name of this thread group.

Returns:

the group's name

getParent

public final ThreadGroup getParent()

Returns this thread group's parent ThreadGroup. It can be null if this is the the root ThreadGroup.

Returns:

the parent

interrupt

public final void interrupt()

Interrupts every Thread in this group and recursively in all its subgroups.

See Also:

Thread.interrupt()

isDaemon

public final boolean isDaemon()

Checks whether this thread group is a daemon ThreadGroup.

Returns:

true if this thread group is a daemon ThreadGroup

See Also:

setDaemon(boolean), destroy()

isDestroyed

public boolean isDestroyed()

Checks whether this thread group has already been destroyed.

Returns:

true if this thread group has already been destroyed

See Also:

destroy()

list

public void list()

Outputs to System.out a text representation of the hierarchy of Threads and ThreadGroups in this thread group (and recursively). Proper indentation is used to show the nesting of groups inside groups and threads inside groups.

parentOf

public final boolean parentOf(ThreadGroup g)

Checks whether this thread group is a direct or indirect parent group of a given ThreadGroup.

Parameters:

g - the potential child ThreadGroup

Returns:

true if this thread group is parent of g

resume

@Deprecated
public final void resume()

Deprecated. Requires deprecated method Thread.resume().

Resumes every thread in this group and recursively in all its subgroups.

See Also:

Thread.resume(), suspend()

setDaemon

public final void setDaemon(boolean isDaemon)

Sets whether this is a daemon ThreadGroup or not. Daemon thread groups are automatically destroyed when they become empty.

Parameters:

isDaemon - the new value

See Also:

isDaemon, destroy()

setMaxPriority

public final void setMaxPriority(int newMax)

Configures the maximum allowed priority for a Thread in this group and recursively in all its subgroups.

A caller can never increase the maximum priority of a thread group. Such an attempt will not result in an exception, it will simply leave the thread group with its current maximum priority.

Parameters:

newMax - the new maximum priority to be set

Throws:

IllegalArgumentException - if the new priority is greater than Thread.MAX_PRIORITY or less than Thread.MIN_PRIORITY

See Also:

getMaxPriority()

stop

@Deprecated
public final void stop()

Deprecated. Requires deprecated method Thread.stop().

Stops every thread in this group and recursively in all its subgroups.

See Also:

Thread.stop(), Thread.stop(Throwable), ThreadDeath

suspend

@Deprecated
public final void suspend()

Deprecated. Requires deprecated method Thread.suspend().

Suspends every thread in this group and recursively in all its subgroups.

See Also:

Thread.suspend(), resume()

toString

public String toString()

Description copied from class: Object

Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression:

   getClass().getName() + '@' + Integer.toHexString(hashCode())

See Writing a useful toString method if you intend implementing your own toString method.

Overrides:

toString in class Object

Returns:

a printable representation of this object.

uncaughtException

public void uncaughtException(Thread t,
                              Throwable e)

Handles uncaught exceptions. Any uncaught exception in any Thread is forwarded to the thread's ThreadGroup by invoking this method.

New code should use Thread.setUncaughtExceptionHandler(java.lang.Thread.UncaughtExceptionHandler) instead of thread groups.

Specified by:

uncaughtException in interface Thread.UncaughtExceptionHandler

Parameters:

t - the Thread that terminated with an uncaught exception

e - the uncaught exception itself