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1: /* EventDispatcher.java -- Dispatch events for prefs 2: Copyright (C) 2006 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package gnu.java.util.prefs; 40: 41: import java.util.ArrayList; 42: 43: /** 44: * This is a helper class used for dispatching events for 45: * the prefs package. 46: */ 47: public class EventDispatcher extends Thread 48: { 49: // This is a singleton class. We dispatch all events via a 50: // new Thread which is created on demand. 51: private static final Thread dispatchThread = new EventDispatcher(); 52: 53: // This is a queue of events to dispatch. This thread waits on 54: // the queue and when notified will remove events until the queue 55: // is empty. 56: private static final ArrayList queue = new ArrayList(); 57: 58: // FIXME: this thread probably ought to go in some classpath-internal 59: // ThreadGroup. But we don't have that yet. 60: private EventDispatcher() 61: { 62: setDaemon(true); 63: start(); 64: } 65: 66: public void run() 67: { 68: while (true) 69: { 70: Runnable r; 71: synchronized (queue) 72: { 73: while (queue.size() == 0) 74: { 75: try 76: { 77: queue.wait(); 78: } 79: catch (InterruptedException _) 80: { 81: // Ignore. 82: } 83: } 84: r = (Runnable) queue.remove(0); 85: } 86: // Invoke outside the synchronization, so that 87: // we aren't blocking other threads from posting events. 88: try 89: { 90: r.run(); 91: } 92: catch (Throwable _) 93: { 94: // Ignore. 95: } 96: } 97: } 98: 99: /** 100: * Add a new runnable to the event dispatch queue. The 101: * runnable will be invoked in the event dispatch queue 102: * without any locks held. 103: * @param runner the Runnable to dispatch 104: */ 105: public static void dispatch(Runnable runner) 106: { 107: synchronized (queue) 108: { 109: queue.add(runner); 110: queue.notify(); 111: } 112: } 113: }