628 lines
20 KiB
Java
628 lines
20 KiB
Java
/* java.lang.ThreadGroup
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Copyright (C) 1998, 2000, 2001 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.lang;
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import java.util.Vector;
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import java.util.Enumeration;
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/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
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* "The Java Language Specification", ISBN 0-201-63451-1
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* plus online API docs for JDK 1.2 from http://www.javasoft.com.
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* Status: Complete for 1.2. Some parts from the JDK 1.0 spec only are
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* not implemented.
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*/
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/**
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* ThreadGroup allows you to group Threads together. There is a
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* hierarchy of ThreadGroups, and only the initial ThreadGroup has
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* no parent. A Thread may access information about its own
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* ThreadGroup, but not its parents or others outside the tree.
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*
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* @author John Keiser
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* @author Tom Tromey
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* @author Bryce McKinlay
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* @version 1.2.0
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* @since JDK1.0
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*/
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public class ThreadGroup
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{
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/* The Initial, top-level ThreadGroup. */
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static ThreadGroup root = new ThreadGroup();
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/* This flag is set if an uncaught exception occurs. The runtime should
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check this and exit with an error status if it is set. */
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static boolean had_uncaught_exception = false;
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private ThreadGroup parent;
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private String name;
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private Vector threads = new Vector();
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private Vector groups = new Vector();
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private boolean daemon_flag = false;
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private int maxpri = Thread.MAX_PRIORITY;
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private ThreadGroup()
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{
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name = "main";
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}
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/** Create a new ThreadGroup using the given name and the
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* current thread's ThreadGroup as a parent.
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* @param name the name to use for the ThreadGroup.
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*/
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public ThreadGroup(String name)
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{
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this (Thread.currentThread().getThreadGroup(), name);
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}
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/** Create a new ThreadGroup using the given name and
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* parent group.
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* @param name the name to use for the ThreadGroup.
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* @param parent the ThreadGroup to use as a parent.
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* @exception NullPointerException if parent is null.
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* @exception SecurityException if you cannot change
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* the intended parent group.
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*/
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public ThreadGroup(ThreadGroup parent, String name)
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{
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parent.checkAccess();
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this.parent = parent;
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if (parent.isDestroyed())
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throw new IllegalArgumentException ();
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this.name = name;
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maxpri = parent.maxpri;
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daemon_flag = parent.daemon_flag;
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parent.addGroup(this);
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}
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/** Get the name of this ThreadGroup.
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* @return the name of this ThreadGroup.
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*/
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public final String getName()
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{
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return name;
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}
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/** Get the parent of this ThreadGroup.
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* @return the parent of this ThreadGroup.
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*/
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public final ThreadGroup getParent()
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{
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return parent;
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}
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/** Set the maximum priority for Threads in this ThreadGroup. setMaxPriority
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* can only be used to reduce the current maximum. If maxpri
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* is greater than the current Maximum, the current value is not changed.
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* Calling this does not effect threads already in this ThreadGroup.
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* @param maxpri the new maximum priority for this ThreadGroup.
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* @exception SecurityException if you cannoy modify this ThreadGroup.
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*/
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public final synchronized void setMaxPriority(int maxpri)
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{
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checkAccess();
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if (maxpri < this.maxpri
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&& maxpri >= Thread.MIN_PRIORITY
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&& maxpri <= Thread.MAX_PRIORITY)
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{
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this.maxpri = maxpri;
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}
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}
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/** Get the maximum priority of Threads in this ThreadGroup.
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* @return the maximum priority of Threads in this ThreadGroup.
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*/
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public final int getMaxPriority()
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{
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return maxpri;
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}
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/** Set whether this ThreadGroup is a daemon group. A daemon
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* group will be destroyed when its last thread is stopped and
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* its last thread group is destroyed.
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* @specnote The Java API docs indicate that the group is destroyed
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* when either of those happen, but that doesn't make
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* sense.
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* @param daemon whether this ThreadGroup should be a daemon group.
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* @exception SecurityException if you cannoy modify this ThreadGroup.
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*/
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public final void setDaemon (boolean daemon)
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{
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checkAccess();
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daemon_flag = daemon;
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}
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/** Tell whether this ThreadGroup is a daemon group. A daemon
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* group will be destroyed when its last thread is stopped and
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* its last thread group is destroyed.
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* @specnote The Java API docs indicate that the group is destroyed
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* when either of those happen, but that doesn't make
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* sense.
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* @return whether this ThreadGroup is a daemon group.
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*/
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public final boolean isDaemon()
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{
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return daemon_flag;
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}
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/** Tell whether this ThreadGroup has been destroyed or not.
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* @return whether this ThreadGroup has been destroyed or not.
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*/
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public synchronized boolean isDestroyed()
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{
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return parent == null && this != root;
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}
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/** Check whether this ThreadGroup is an ancestor of the
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* specified ThreadGroup, or if they are the same.
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*
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* @param g the group to test on.
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* @return whether this ThreadGroup is a parent of the
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* specified group.
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*/
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public final boolean parentOf(ThreadGroup tg)
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{
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while (tg != null)
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{
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if (tg == this)
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return true;
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tg = tg.parent;
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}
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return false;
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}
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/** Return the total number of active threads in this ThreadGroup
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* and all its descendants.<P>
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*
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* This cannot return an exact number, since the status of threads
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* may change after they were counted. But it should be pretty
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* close.<P>
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*
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* @return the number of active threads in this ThreadGroup and
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* its descendants.
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* @specnote it isn't clear what the definition of an "Active" thread is.
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* Current JDKs regard a thread as active if has been
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* started and not finished. We implement this behaviour.
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* There is a JDC bug, <A HREF="http://developer.java.sun.com/developer/bugParade/bugs/4089701.html">
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* 4089701</A>, regarding this issue.
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*
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*/
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public synchronized int activeCount()
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{
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int total = 0;
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for (int i = 0; i < threads.size(); ++i)
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{
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if (((Thread) threads.elementAt(i)).isAlive ())
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++total;
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}
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for (int i=0; i < groups.size(); i++)
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{
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ThreadGroup g = (ThreadGroup) groups.elementAt(i);
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total += g.activeCount();
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}
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return total;
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}
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/** Get the number of active groups in this ThreadGroup. This group
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* itself is not included in the count.
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* @specnote it is unclear what exactly constitutes an
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* active ThreadGroup. Currently we assume that
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* all sub-groups are active, per current JDKs.
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* @return the number of active groups in this ThreadGroup.
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*/
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public synchronized int activeGroupCount()
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{
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int total = groups.size();
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for (int i=0; i < groups.size(); i++)
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{
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ThreadGroup g = (ThreadGroup) groups.elementAt(i);
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total += g.activeGroupCount();
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}
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return total;
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}
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/** Copy all of the active Threads from this ThreadGroup and
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* its descendants into the specified array. If the array is
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* not big enough to hold all the Threads, extra Threads will
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* simply not be copied.
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*
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* @param threads the array to put the threads into.
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* @return the number of threads put into the array.
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*/
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public int enumerate(Thread[] threads)
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{
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return enumerate(threads, 0, true);
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}
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/** Copy all of the active Threads from this ThreadGroup and,
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* if desired, from its descendants, into the specified array.
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* If the array is not big enough to hold all the Threads,
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* extra Threads will simply not be copied.
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*
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* @param threads the array to put the threads into.
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* @param useDescendants whether to count Threads in this
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* ThreadGroup's descendants or not.
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* @return the number of threads put into the array.
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*/
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public int enumerate(Thread[] threads, boolean useDescendants)
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{
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return enumerate(threads, 0, useDescendants);
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}
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// This actually implements enumerate.
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private synchronized int enumerate(Thread[] list, int next_index,
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boolean recurse)
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{
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Enumeration e = threads.elements();
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while (e.hasMoreElements() && next_index < list.length)
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{
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Thread t = (Thread) e.nextElement();
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if (t.isAlive ())
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list[next_index++] = t;
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}
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if (recurse && next_index != list.length)
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{
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e = groups.elements();
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while (e.hasMoreElements() && next_index < list.length)
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{
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ThreadGroup g = (ThreadGroup) e.nextElement();
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next_index = g.enumerate(list, next_index, true);
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}
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}
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return next_index;
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}
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/** Copy all active ThreadGroups that are descendants of this
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* ThreadGroup into the specified array. If the array is not
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* large enough to hold all active ThreadGroups, extra
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* ThreadGroups simply will not be copied.
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*
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* @param groups the array to put the ThreadGroups into.
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* @return the number of ThreadGroups copied into the array.
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*/
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public int enumerate(ThreadGroup[] groups)
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{
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return enumerate(groups, 0, true);
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}
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/** Copy all active ThreadGroups that are children of this
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* ThreadGroup into the specified array, and if desired, also
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* copy all active descendants into the array. If the array
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* is not large enough to hold all active ThreadGroups, extra
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* ThreadGroups simply will not be copied.
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*
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* @param groups the array to put the ThreadGroups into.
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* @param recurse whether to include all descendants
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* of this ThreadGroup's children in determining
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* activeness.
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* @return the number of ThreadGroups copied into the array.
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*/
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public int enumerate(ThreadGroup[] groups, boolean recurse)
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{
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return enumerate(groups, 0, recurse);
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}
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// This actually implements enumerate.
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private synchronized int enumerate (ThreadGroup[] list, int next_index,
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boolean recurse)
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{
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Enumeration e = groups.elements();
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while (e.hasMoreElements() && next_index < list.length)
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{
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ThreadGroup g = (ThreadGroup) e.nextElement();
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list[next_index++] = g;
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if (recurse && next_index != list.length)
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next_index = g.enumerate(list, next_index, true);
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}
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return next_index;
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}
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/** Interrupt all Threads in this ThreadGroup and its sub-groups.
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* @exception SecurityException if you cannot modify this
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* ThreadGroup or any of its Threads or children
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* ThreadGroups.
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* @since JDK1.2
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*/
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public final synchronized void interrupt()
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{
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checkAccess();
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for (int i=0; i < threads.size(); i++)
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{
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Thread t = (Thread) threads.elementAt(i);
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t.interrupt();
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}
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for (int i=0; i < groups.size(); i++)
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{
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ThreadGroup tg = (ThreadGroup) groups.elementAt(i);
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tg.interrupt();
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}
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}
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/** Stop all Threads in this ThreadGroup and its descendants.
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* @exception SecurityException if you cannot modify this
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* ThreadGroup or any of its Threads or children
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* ThreadGroups.
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* @deprecated This method calls Thread.stop(), which is dangerous.
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*/
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public final synchronized void stop()
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{
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checkAccess();
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for (int i=0; i<threads.size(); i++)
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{
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Thread t = (Thread) threads.elementAt(i);
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t.stop();
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}
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for (int i=0; i < groups.size(); i++)
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{
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ThreadGroup tg = (ThreadGroup) groups.elementAt(i);
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tg.stop();
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}
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}
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/** Suspend all Threads in this ThreadGroup and its descendants.
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* @exception SecurityException if you cannot modify this
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* ThreadGroup or any of its Threads or children
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* ThreadGroups.
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* @deprecated This method calls Thread.suspend(), which is dangerous.
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*/
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public final synchronized void suspend()
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{
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checkAccess();
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for (int i=0; i<threads.size(); i++)
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{
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Thread t = (Thread) threads.elementAt(i);
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t.suspend();
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}
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for (int i=0; i < groups.size(); i++)
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{
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ThreadGroup tg = (ThreadGroup) groups.elementAt(i);
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tg.suspend();
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}
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}
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/** Resume all Threads in this ThreadGroup and its descendants.
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* @exception SecurityException if you cannot modify this
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* ThreadGroup or any of its Threads or children
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* ThreadGroups.
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* @deprecated This method relies on Thread.suspend(), which is dangerous.
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*/
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public final synchronized void resume()
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{
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checkAccess();
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for (int i=0; i < threads.size(); i++)
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{
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Thread t = (Thread) threads.elementAt(i);
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t.resume();
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}
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for (int i=0; i < groups.size(); i++)
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{
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ThreadGroup tg = (ThreadGroup) groups.elementAt(i);
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tg.resume();
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}
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}
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// This is a helper that is used to implement the destroy method.
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private synchronized void checkDestroy ()
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{
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if (! threads.isEmpty())
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throw new IllegalThreadStateException ("ThreadGroup has threads");
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for (int i=0; i < groups.size(); i++)
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{
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ThreadGroup tg = (ThreadGroup) groups.elementAt(i);
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tg.checkDestroy();
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}
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}
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/** Destroy this ThreadGroup. There can be no Threads in it,
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* and none of its descendants (sub-groups) may have Threads in them.
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* All its descendants will be destroyed as well.
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* @exception IllegalThreadStateException if the ThreadGroup or
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* its descendants have Threads remaining in them, or
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* if the ThreadGroup in question is already destroyed.
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* @exception SecurityException if you cannot modify this
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* ThreadGroup or any of its descendants.
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*/
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public final synchronized void destroy()
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{
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checkAccess();
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if (isDestroyed())
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throw new IllegalThreadStateException("Already destroyed.");
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checkDestroy ();
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if (parent != null)
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parent.removeGroup(this);
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parent = null;
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for (int i=0; i < groups.size(); i++)
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{
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ThreadGroup tg = (ThreadGroup) groups.elementAt(i);
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tg.destroy();
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}
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}
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/** Print out information about this ThreadGroup to System.out.
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*/
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public void list()
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{
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list("");
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}
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private synchronized void list(String indentation)
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{
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System.out.print(indentation);
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System.out.println(toString ());
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String sub = indentation + " ";
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for (int i=0; i < threads.size(); i++)
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{
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Thread t = (Thread) threads.elementAt(i);
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System.out.print(sub);
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System.out.println(t.toString());
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}
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for (int i=0; i < groups.size(); i++)
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{
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ThreadGroup tg = (ThreadGroup) groups.elementAt(i);
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tg.list(sub);
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}
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}
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/** When a Thread in this ThreadGroup does not catch an exception,
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* this method of the ThreadGroup is called.<P>
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*
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* ThreadGroup's implementation does the following:<BR>
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* <OL>
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* <LI>If there is a parent ThreadGroup, call uncaughtException()
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* in the parent.</LI>
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* <LI>If the Throwable passed is a ThreadDeath, don't do
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* anything.</LI>
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* <LI>Otherwise, call <CODE>exception.printStackTrace().</CODE></LI>
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* </OL>
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*
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* @param thread the thread that exited.
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* @param exception the uncaught exception.
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*/
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public void uncaughtException(Thread thread, Throwable t)
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{
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if (parent != null)
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parent.uncaughtException (thread, t);
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else if (! (t instanceof ThreadDeath))
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{
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if (thread != null)
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System.err.print ("Exception in thread \""
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+ thread.getName() + "\" ");
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try
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{
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t.printStackTrace(System.err);
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}
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catch (Throwable x)
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{
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// This means that something is badly screwed up with the runtime,
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// or perhaps someone is messing with the SecurityManager. In any
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// case, try to deal with it gracefully.
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System.err.println(t);
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System.err.println("*** Got " + x.toString() +
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" while trying to print stack trace");
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}
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had_uncaught_exception = true;
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}
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}
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/** Tell the VM whether it may suspend Threads in low memory
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* situations.
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* @deprecated This method is unimplemented, because it would rely on
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* suspend(), which is deprecated. There is no way for a Java
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* program to determine whether this has any effect whatsoever,
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* so we don't need it.
|
|
* @return false
|
|
*/
|
|
public boolean allowThreadSuspension(boolean allow)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
/** Get a human-readable representation of this ThreadGroup.
|
|
* @return a String representing this ThreadGroup.
|
|
* @specnote Language Spec and Class Libraries book disagree a bit here.
|
|
* We follow the Spec, but add "ThreadGroup" per the book. We
|
|
* include "java.lang" based on the list() example in the Class
|
|
* Libraries book.
|
|
*/
|
|
public String toString ()
|
|
{
|
|
return "java.lang.ThreadGroup[name=" + name +
|
|
",maxpri=" + maxpri + "]";
|
|
}
|
|
|
|
/** Find out if the current Thread can modify this ThreadGroup.
|
|
* Calls the current SecurityManager's checkAccess() method to
|
|
* find out. If there is none, it assumes everything's OK.
|
|
* @exception SecurityException if the current Thread cannot
|
|
* modify this ThreadGroup.
|
|
*/
|
|
public final void checkAccess()
|
|
{
|
|
SecurityManager sm = System.getSecurityManager();
|
|
if (sm != null)
|
|
sm.checkAccess(this);
|
|
}
|
|
|
|
// This is called to add a Thread to our internal list.
|
|
final synchronized void addThread(Thread t)
|
|
{
|
|
if (isDestroyed())
|
|
throw new IllegalThreadStateException ("ThreadGroup is destroyed");
|
|
|
|
threads.addElement(t);
|
|
}
|
|
|
|
// This is called to remove a Thread from our internal list.
|
|
final synchronized void removeThread(Thread t)
|
|
{
|
|
if (isDestroyed())
|
|
throw new IllegalThreadStateException ();
|
|
|
|
threads.removeElement(t);
|
|
// Daemon groups are automatically destroyed when all their threads die.
|
|
if (daemon_flag && groups.size() == 0 && threads.size() == 0)
|
|
{
|
|
// We inline destroy to avoid the access check.
|
|
if (parent != null)
|
|
parent.removeGroup(this);
|
|
parent = null;
|
|
}
|
|
}
|
|
|
|
// This is called to add a ThreadGroup to our internal list.
|
|
final synchronized void addGroup(ThreadGroup g)
|
|
{
|
|
groups.addElement(g);
|
|
}
|
|
|
|
// This is called to remove a ThreadGroup from our internal list.
|
|
final synchronized void removeGroup(ThreadGroup g)
|
|
{
|
|
groups.removeElement(g);
|
|
// Daemon groups are automatically destroyed when all their threads die.
|
|
if (daemon_flag && groups.size() == 0 && threads.size() == 0)
|
|
{
|
|
// We inline destroy to avoid the access check.
|
|
if (parent != null)
|
|
parent.removeGroup(this);
|
|
parent = null;
|
|
}
|
|
}
|
|
}
|