Returns an estimate of the number of active threads in this thread group.

  Returns an estimate of the number of active threads in this thread group. The result might not reflect concurrent activity, and might be affected by the presence of certain system threads.

Due to the inherently imprecise nature of the result, it is recommended that this method only be used for informational purposes.
Returns: an estimate of the number of active threads in this thread group and in any other thread group that has this thread group as an ancestor.
Since: JDK1.0

  Returns an estimate of the number of active groups in this thread group.

  Returns an estimate of the number of active groups in this thread group. The result might not reflect concurrent activity.

Due to the inherently imprecise nature of the result, it is recommended that this method only be used for informational purposes.
Returns: the number of active thread groups with this thread group as an ancestor.
Since: JDK1.0

  Adds the specified Thread to this group.

  Adds the specified Thread to this group.
Parameters:
- t - the Thread to be added
Throws:
- IllegalThreadStateException - If the Thread group has been destroyed.

  Increments the count of unstarted threads in the thread group.

  Increments the count of unstarted threads in the thread group.
Unstarted threads are not added to the thread group so that they
can be collected if they are never started, but they must be
counted so that daemon thread groups with unstarted threads in
them are not destroyed.

  Used by VM to control lowmem implicit suspension.

  Used by VM to control lowmem implicit suspension.
Returns: true on success
Parameters:
- b - boolean to allow or disallow suspension
Since: JDK1.1

  Determines if the currently running thread has permission to modify this thread group.

  Determines if the currently running thread has permission to modify this thread group.

If there is a security manager, its checkAccess method is called with this thread group as its argument. This may result in throwing a SecurityException.
Throws:
- SecurityException - if the current thread is not allowed to access this thread group.
Since: JDK1.0
See Also: SecurityManager.checkAccess(java.lang.ThreadGroup),

  Destroys this thread group and all of its subgroups.

  Destroys this thread group and all of its subgroups. This thread group must be empty, indicating that all threads that had been in this thread group have since stopped.

First, the checkAccess method of this thread group is called with no arguments; this may result in a security exception.
Throws:
- IllegalThreadStateException - if the thread group is not empty or if the thread group has already been destroyed.
- SecurityException - if the current thread cannot modify this thread group.
Since: JDK1.0
See Also: ThreadGroup.checkAccess(),

  Copies into the specified array every active thread in this thread group and its subgroups.

  Copies into the specified array every active thread in this thread group and its subgroups.

First, the checkAccess method of this thread group is called with no arguments; this may result in a security exception.

An application might use the 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 this thread group and its subgroups, the caller should verify that the returned int value is strictly less than the length of list.

Due to the inherent race condition in this method, it is recommended that the method only be used for informational purposes.
Returns: the number of threads put into the array.
Parameters:
- list - an array into which to place the list of threads.
Throws:
- SecurityException - if the current thread does not have permission to enumerate this thread group.
Since: JDK1.0
See Also: ThreadGroup.activeCount(), ThreadGroup.checkAccess(),

  Copies into the specified array every active thread in this thread group.

  Copies into the specified array every active thread in this thread group. If the recurse flag is true, references to every active thread in this thread's subgroups are also included. If the array is too short to hold all the threads, the extra threads are silently ignored.

First, the checkAccess method of this thread group is called with no arguments; this may result in a security exception.

An application might use the 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 this thread group, the caller should verify that the returned int value is strictly less than the length of list.

Due to the inherent race condition in this method, it is recommended that the method only be used for informational purposes.
Returns: the number of threads placed into the array.
Parameters:
- list - an array into which to place the list of threads.
- recurse - a flag indicating whether also to include threads in thread groups that are subgroups of this thread group.
Throws:
- SecurityException - if the current thread does not have permission to enumerate this thread group.
Since: JDK1.0
See Also: ThreadGroup.activeCount(), ThreadGroup.checkAccess(),

  Copies into the specified array references to every active subgroup in this thread group.

  Copies into the specified array references to every active subgroup in this thread group.

First, the checkAccess method of this thread group is called with no arguments; this may result in a security exception.

An application might use the activeGroupCount method to get an estimate of how big the array should be, however if the array is too short to hold all the thread groups, the extra thread groups are silently ignored. If it is critical to obtain every active subgroup in this thread group, the caller should verify that the returned int value is strictly less than the length of list.

Due to the inherent race condition in this method, it is recommended that the method only be used for informational purposes.
Returns: the number of thread groups put into the array.
Parameters:
- list - an array into which to place the list of thread groups.
Throws:
- SecurityException - if the current thread does not have permission to enumerate this thread group.
Since: JDK1.0
See Also: ThreadGroup.activeGroupCount(), ThreadGroup.checkAccess(),

  Copies into the specified array references to every active subgroup in this thread group.

  Copies into the specified array references to every active subgroup in this thread group. If the recurse flag is true, references to all active subgroups of the subgroups and so forth are also included.

First, the checkAccess method of this thread group is called with no arguments; this may result in a security exception.

An application might use the activeGroupCount method to get an estimate of how big the array should be, however if the array is too short to hold all the thread groups, the extra thread groups are silently ignored. If it is critical to obtain every active subgroup in this thread group, the caller should verify that the returned int value is strictly less than the length of list.

Due to the inherent race condition in this method, it is recommended that the method only be used for informational purposes.
Returns: the number of thread groups put into the array.
Parameters:
- list - an array into which to place the list of threads.
- recurse - a flag indicating whether to recursively enumerate all included thread groups.
Throws:
- SecurityException - if the current thread does not have permission to enumerate this thread group.
Since: JDK1.0
See Also: ThreadGroup.activeGroupCount(), ThreadGroup.checkAccess(),

  Returns the maximum priority of this thread group.

  Returns the maximum priority of this thread group. Threads that are
part of this group cannot have a higher priority than the maximum
priority.
Returns: the maximum priority that a thread in this thread group can have.
Since: JDK1.0
See Also: ThreadGroup.setMaxPriority(int),

  Returns the name of this thread group.

  Returns the name of this thread group.
Returns: the name of this thread group.
Since: JDK1.0

  Returns the parent of this thread group.

  Returns the parent of this thread group.

First, if the parent is not null, the checkAccess method of the parent thread group is called with no arguments; this may result in a security exception.
Returns: the parent of this thread group. The top-level thread group is the only thread group whose parent is null.
Throws:
- SecurityException - if the current thread cannot modify this thread group.
Since: JDK1.0
See Also: ThreadGroup.checkAccess(), SecurityException, RuntimePermission,

  Interrupts all threads in this thread group.

  Interrupts all threads in this thread group.

First, the checkAccess method of this thread group is called with no arguments; this may result in a security exception.

This method then calls the interrupt method on all the threads in this thread group and in all of its subgroups.
Throws:
- SecurityException - if the current thread is not allowed to access this thread group or any of the threads in the thread group.
Since: 1.2
See Also: Thread.interrupt(), SecurityException, ThreadGroup.checkAccess(),

  Tests if this thread group is a daemon thread group.

  Tests if this thread group is a daemon thread group. A
daemon thread group is automatically destroyed when its last
thread is stopped or its last thread group is destroyed.
Returns: true if this thread group is a daemon thread group; false otherwise.
Since: JDK1.0

  Tests if this thread group has been destroyed.

  Tests if this thread group has been destroyed.
Returns: true if this object is destroyed
Since: JDK1.1

  Prints information about this thread group to the standard output.

  Prints information about this thread group to the standard
output. This method is useful only for debugging.
Since: JDK1.0

  Tests if this thread group is either the thread group argument or one of its ancestor thread groups.

  Tests if this thread group is either the thread group
argument or one of its ancestor thread groups.
Returns: true if this thread group is the thread group argument or one of its ancestor thread groups; false otherwise.
Parameters:
- g - a thread group.
Since: JDK1.0

  Removes the specified Thread from this group.

  Removes the specified Thread from this group.
Returns: if the Thread has already been destroyed.
Parameters:
- t - the Thread to be removed

  Resumes all threads in this thread group.

  Resumes all threads in this thread group.

First, the checkAccess method of this thread group is called with no arguments; this may result in a security exception.

This method then calls the resume method on all the threads in this thread group and in all of its sub groups.
Throws:
- SecurityException - if the current thread is not allowed to access this thread group or any of the threads in the thread group.
Since: JDK1.0
See Also: SecurityException, Thread.resume(), ThreadGroup.checkAccess(),

  Changes the daemon status of this thread group.

  Changes the daemon status of this thread group.

First, the checkAccess method of this thread group is called with no arguments; this may result in a security exception.

A daemon thread group is automatically destroyed when its last thread is stopped or its last thread group is destroyed.
Parameters:
- daemon - if true, marks this thread group as a daemon thread group; otherwise, marks this thread group as normal.
Throws:
- SecurityException - if the current thread cannot modify this thread group.
Since: JDK1.0
See Also: SecurityException, ThreadGroup.checkAccess(),

  Sets the maximum priority of the group.

  Sets the maximum priority of the group. Threads in the thread group that already have a higher priority are not affected.

First, the checkAccess method of this thread group is called with no arguments; this may result in a security exception.

If the pri argument is less than Thread.MIN_PRIORITY or greater than Thread.MAX_PRIORITY, the maximum priority of the group remains unchanged.

Otherwise, the priority of this ThreadGroup object is set to the smaller of the specified pri and the maximum permitted priority of the parent of this thread group. (If this thread group is the system thread group, which has no parent, then its maximum priority is simply set to pri.) Then this method is called recursively, with pri as its argument, for every thread group that belongs to this thread group.
Parameters:
- pri - the new priority of the thread group.
Throws:
- SecurityException - if the current thread cannot modify this thread group.
Since: JDK1.0
See Also: ThreadGroup.getMaxPriority(), SecurityException, ThreadGroup.checkAccess(),

  Stops all threads in this thread group.

  Stops all threads in this thread group.

First, the checkAccess method of this thread group is called with no arguments; this may result in a security exception.

This method then calls the stop method on all the threads in this thread group and in all of its subgroups.
Throws:
- SecurityException - if the current thread is not allowed to access this thread group or any of the threads in the thread group.
Since: JDK1.0
See Also: SecurityException, Thread.stop(), ThreadGroup.checkAccess(),

  Suspends all threads in this thread group.

  Suspends all threads in this thread group.

First, the checkAccess method of this thread group is called with no arguments; this may result in a security exception.

This method then calls the suspend method on all the threads in this thread group and in all of its subgroups.
Throws:
- SecurityException - if the current thread is not allowed to access this thread group or any of the threads in the thread group.
Since: JDK1.0
See Also: Thread.suspend(), SecurityException, ThreadGroup.checkAccess(),

  Returns a string representation of this Thread group.

  Returns a string representation of this Thread group.
Returns: a string representation of this thread group.
Since: JDK1.0

  Called by the Java Virtual Machine when a thread in this thread group stops because of an uncaught exception, and the thread does not have a specific Thread.UncaughtExceptionHandler installed.

  Called by the Java Virtual Machine when a thread in this thread group stops because of an uncaught exception, and the thread does not have a specific Thread.UncaughtExceptionHandler installed.

The uncaughtException method of ThreadGroup does the following:

• If this thread group has a parent thread group, the uncaughtException method of that parent is called with the same two arguments.
• Otherwise, this method checks to see if there is a default uncaught exception handler installed, and if so, its uncaughtException method is called with the same two arguments.
• Otherwise, this method determines if the Throwable argument is an instance of ThreadDeath. If so, nothing special is done. Otherwise, a message containing the thread's name, as returned from the thread's getName method, and a stack backtrace, using the Throwable's printStackTrace method, is printed to the standard error stream.

Applications can override this method in subclasses of ThreadGroup to provide alternative handling of uncaught exceptions.
Parameters:
- t - the thread that is about to exit.
- e - the uncaught exception.
Since: JDK1.0