midletmap.java

有关j2me的很好的例子可以研究一下

/*
 * @(#)MIDLetMap.java	1.9 01/08/12
 *
 * Copyright (c) 2000-2001 Sun Microsystems, Inc., 901 San Antonio Road,
 * Palo Alto, CA 94303, U.S.A.  All Rights Reserved.
 *
 * Sun Microsystems, Inc. has intellectual property rights relating
 * to the technology embodied in this software.  In particular, and
 * without limitation, these intellectual property rights may include
 * one or more U.S. patents, foreign patents, or pending
 * applications.  Sun, Sun Microsystems, the Sun logo, Java, KJava,
 * and all Sun-based and Java-based marks are trademarks or
 * registered trademarks of Sun Microsystems, Inc.  in the United
 * States and other countries.
 *
 * This software is distributed under licenses restricting its use,
 * copying, distribution, and decompilation.  No part of this
 * software may be reproduced in any form by any means without prior
 * written authorization of Sun and its licensors, if any.
 *
 * FEDERAL ACQUISITIONS:  Commercial Software -- Government Users
 * Subject to Standard License Terms and Conditions
 */

package com.sun.midp.lcdui;

import javax.microedition.midlet.MIDlet;
import java.util.Hashtable;

/**
 * A class that maps between DisplayAccess objects and MIDlets.
 * In future versions of the MIDP spec, MIDlet may have been
 * removed, in which case this will either map directly between 
 * DisplayAccess and MIDLet, or it may be that this class isn't needed.
 */
public class MIDLetMap {
    /** Table to store the midlet map in */
    static private Hashtable table = new Hashtable();

    /**
     * Associate the given MIDlet and DisplayAccess.  This is a
     * two-way association, i.e. you can look up either one wrt the other.
     *
     * @param m The Midlet to store
     * @param d The DisplayAccess associated with the MIDlet
     */
    public static void put(MIDlet m, DisplayAccess d) {
        table.put(m, d);
        table.put(d, m);
    }

    /**
     * Remove any references to the given MIDlet from the map so it can be
     * garbage collected.
     *
     * @param m The MIDlet to remove from the map
     */
    public static void remove(MIDlet m) {
        DisplayAccess d;

        d = get(m);
        table.remove(m);
        if (d == null) {
            return;
        }

        table.remove(d);
    }

    /**
     * Get the DisplayAccess object for this MIDlet.
     *
     * @param m The MIDlet to get the DisplayAccess for
     * @return DisplayAccess The DisplayAccess associated with the MIDlet
     */
    public static DisplayAccess get(MIDlet m) {
        return (DisplayAccess) table.get(m);
    }

    /**
     * Get the MIDlet for this DisplayAcess object.
     *
     * @param d The DisplayAccess to get the MIDlet for
     * @return MIDlet The MIDlet associated with this DisplayAccess
     */
    public static MIDlet get(DisplayAccess d) {
        return (MIDlet) table.get(d);
    }
}