se.lth.cs.realtime
Class RTThreadGroup

java.lang.Object
  |
  +--se.lth.cs.realtime.RTThreadGroup

public class RTThreadGroup

extends java.lang.Object

A thread group represents a set of threads. In addition, a thread group can also include other thread groups. The thread groups form a tree in which every thread group except the initial thread group has a parent.

This class is mainly aimed at giving a more convenient way to issue the same function call to several threads, which is often needed. It poses also the basis for an optional, future implentation of some kind of security policy, as in the standard Java API.

Constructor Summary

RTThreadGroup(RTThreadGroup parent, java.lang.String name)
Creates a new thread group.

RTThreadGroup(java.lang.String name)
Constructs a new thread group.

Method Summary

int	activeCount() Returns an estimate of the number of active threads in this thread group.
int	activeGroupCount() Returns an estimate of the number of active groups in this thread group.
void	destroy() Destroys this thread group and all of its subgroups.
int	enumerate(RTThreadGroup[] list) Copies into the specified array references to every active subgroup in this thread group.
int	enumerate(RTThreadGroup[] list, boolean recurse) Copies into the specified array references to every active subgroup in this thread group.
int	enumerate(java.lang.Thread[] list) Copies into the specified array every active thread in this thread group and its subgroups.
int	enumerate(java.lang.Thread[] list, boolean recurse) Copies into the specified array every active thread in this thread group.
int	getMaxPriority() Returns the maximum priority of this thread group.
int	getMinPriority() Returns the minimum priority of this thread group.
java.lang.String	getName() Returns the name of this thread group.
RTThreadGroup	getParent() Returns the parent of this thread group.
void	interrupt() Interrupts all threads in this thread group.
boolean	isDaemon() Tests if this thread group is a daemon thread group.
boolean	isDestroyed() Tests if this thread group has been destroyed.
void	list() Prints information about this thread group to the standard output.
boolean	parentOf(RTThreadGroup g) Tests if this thread group is either the thread group argument or one of its ancestor thread groups.
void	setDaemon(boolean daemon) Changes the daemon status of this thread group.
void	setMaxPriority(int pri) Sets the maximum priority of the group.
void	setMinPriority(int pri) Sets the minimum priority of the group.
java.lang.String	toString() Returns a string representation of this Thread group.
void	uncaughtException(java.lang.Thread t, java.lang.Throwable e) Called by the Java Virtual Machine when a thread in this thread group stops because of an uncaught exception.

Methods inherited from class java.lang.Object

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

Constructor Detail

RTThreadGroup

public RTThreadGroup(java.lang.String name)

Constructs a new thread group. The parent of this new group is the thread group of the currently running thread.

Parameters:

name - the name of the new thread group.

RTThreadGroup

public RTThreadGroup(RTThreadGroup parent,
                     java.lang.String name)

Creates a new thread group. The parent of this new group is the specified thread group.

Parameters:

parent - the parent thread group.

name - the name of the new thread group.

Throws:

NullPointerException - if the thread group argument is null.

Method Detail

getName

public final java.lang.String getName()

Returns the name of this thread group.

Returns:

the name of this thread group.

getParent

public final RTThreadGroup getParent()

Returns the parent of this thread group.

Returns:

the parent of this thread group. The top-level thread group is the only thread group whose parent is null.

getMaxPriority

public final int getMaxPriority()

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.

getMinPriority

public final int getMinPriority()

Returns the minimum priority of this thread group. Threads that are part of this group cannot have a lower priority than the minimum priority.

Returns:

the minimum priority that a thread in this thread group can have.

isDaemon

public final boolean isDaemon()

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.

isDestroyed

public boolean isDestroyed()

Tests if this thread group has been destroyed.

setDaemon

public final void setDaemon(boolean daemon)

Changes the daemon status of this thread group.

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.

setMaxPriority

public final void setMaxPriority(int pri)

Sets the maximum priority of the group.

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

Parameters:

pri - the new priority of the thread group.

setMinPriority

public final void setMinPriority(int pri)

Sets the minimum priority of the group.

Threads in the thread group that already have a lower priority are not affected.

Parameters:

pri - the new priority of the thread group.

parentOf

public final boolean parentOf(RTThreadGroup g)

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

Parameters:

g - a thread group.

Returns:

true if this thread group is the thread group argument or one of its ancestor thread groups; false otherwise.

activeCount

public int activeCount()

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

Returns:

the number of active threads in this thread group and in any other thread group that has this thread group as an ancestor.

enumerate

public int enumerate(java.lang.Thread[] list)

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

An application should use the activeCount method to get an estimate of how big the array should be. If the array is too short to hold all the threads, the extra threads are silently ignored.

Parameters:

list - an array into which to place the list of threads.

Returns:

the number of threads put into the array.

See Also:

ThreadGroup.activeCount()

enumerate

public int enumerate(java.lang.Thread[] list,
                     boolean recurse)

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.

An application should use the activeCount method to get an estimate of how big the array should be.

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.

Returns:

the number of threads placed into the array.

Since:

JDK1.0

See Also:

ThreadGroup.activeCount()

activeGroupCount

public int activeGroupCount()

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

Returns:

the number of active thread groups with this thread group as an ancestor.

enumerate

public int enumerate(RTThreadGroup[] list)

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

An application should use the activeGroupCount method to get an estimate of how big the array should be. If the array is too short to hold all the thread groups, the extra thread groups are silently ignored.

Parameters:

list - an array into which to place the list of thread groups.

Returns:

the number of thread groups put into the array.

See Also:

ThreadGroup.activeGroupCount()

enumerate

public int enumerate(RTThreadGroup[] list,
                     boolean recurse)

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.

An application should use the activeGroupCount method to get an estimate of how big the array should be.

Parameters:

list - an array into which to place the list of threads.

recurse - a flag indicating whether to recursively enumerate all included thread groups.

Returns:

the number of thread groups put into the array.

See Also:

ThreadGroup.activeGroupCount()

interrupt

public final void interrupt()

Interrupts all threads in this thread group.

This method calls the interrupt method on all the threads in this thread group and in all of its subgroups.

See Also:

RTThread.interrupt()

destroy

public final void destroy()

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.

Throws:

IllegalThreadStateException - if the thread group is not empty or if the thread group has already been destroyed.

list

public void list()

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

Since:

JDK1.0

uncaughtException

public void uncaughtException(java.lang.Thread t,
                              java.lang.Throwable e)

Called by the Java Virtual Machine when a thread in this thread group stops because of an uncaught exception.

The uncaughtException method of RTThreadGroup 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 determines if the Throwable argument is an instance of ThreadDeath. If so, nothing special is done. Otherwise, the Throwable's printStackTrace method is called to print a stack backtrace to the standard error stream.

Applications can override this method in subclasses of RTThreadGroup to provide alternative handling of uncaught exceptions.

Parameters:

t - the thread that is about to exit.

e - the uncaught exception.

See Also:

java.lang.System#err, java.lang.ThreadDeath, Throwable.printStackTrace(java.io.PrintStream)

toString

public java.lang.String toString()

Returns a string representation of this Thread group.

Overrides:

toString in class java.lang.Object

Returns:

a string representation of this thread group.