barriersignaler.java

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//
// This file is part of the OpenNMS(R) Application.
//
// OpenNMS(R) is Copyright (C) 2002-2003 The OpenNMS Group, Inc.  All rights reserved.
// OpenNMS(R) is a derivative work, containing both original code, included code and modified
// code that was published under the GNU General Public License. Copyrights for modified 
// and included code are below.
//
// OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc.
//
// Copyright (C) 1999-2001 Oculan Corp.  All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.                                                            
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//       
// For more information contact: 
//      OpenNMS Licensing       <[e-mail]>
//      http://www.opennms.org/
//      http://www.opennms.com/
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// Tab Stop = 8
//

package org.opennms.netmgt.utils;

/**
 * <P>
 * The Signaler interface was designed to get around the problem of not being
 * able to extend the functionality of the Object.notify and Object.notifyAll
 * methods. In some instances is would be nice to alter the default behavior
 * slightly, the signaler interface allows this to occur.
 * </P>
 * 
 * <P>
 * An object that implements the Signaler interface is used just like a typical
 * object. But instead of using notify and notifyAll, the methods signal and
 * signalAll should be used in their place.
 * </P>
 * 
 * @author <A HREF="mailto:[e-mail]">Weave </A>
 * @author <A HREF="mailto:[e-mail]">Sowmya </A>
 * @author <A HREF="http://www.opennms.org/">OpenNMS </A>
 * 
 */
public final class BarrierSignaler implements Signaler {
    /**
     * The barrier where the signal starts occuring on each call.
     */
    private int m_barrier;

    /**
     * The count of signal calls. This latches at the barrier and does not
     * increment further.
     */
    private int m_counter;

    /**
     * Constructs a new barrier signaler.
     * 
     * @param barrier
     *            The barrier for notification to start.
     * 
     */
    public BarrierSignaler(int barrier) {
        m_barrier = barrier;
        m_counter = 0;
    }

    /**
     * <P>
     * Provides the functionality of the notify method, but may be overridden by
     * the implementor to provide additional functionality.
     * </P>
     * 
     * @see java.lang.Object#notify
     */
    public synchronized void signal() {
        if (++m_counter == m_barrier) {
            --m_counter;
            notify();
        }
    }

    /**
     * <P>
     * Provides the functionality of the notifyAll method, but may be overridden
     * by the implementor to provide additional functionality.
     * </P>
     * 
     * @see java.lang.Object#notifyAll
     */
    public void signalAll() {
        if (++m_counter == m_barrier) {
            --m_counter;
            notifyAll();
        }
    }
}