singletonlist.java

XML的解析、编译、查询等技术的JAVA源代码。

/*
 * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/util/SingletonList.java,v 1.4 2006/11/09 16:39:19 elharo Exp $
 * $Revision: 1.4 $
 * $Date: 2006/11/09 16:39:19 $
 *
 * ====================================================================
 *
 * Copyright 2000-2002 bob mcwhirter & James Strachan.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * 
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 
 *   * Neither the name of the Jaxen Project nor the names of its
 *     contributors may be used to endorse or promote products derived 
 *     from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * ====================================================================
 * This software consists of voluntary contributions made by many 
 * individuals on behalf of the Jaxen Project and was originally 
 * created by bob mcwhirter <[e-mail]> and 
 * James Strachan <[e-mail]>.  For more information on the 
 * Jaxen Project, please see <http://www.jaxen.org/>.
 * 
 * $Id: SingletonList.java,v 1.4 2006/11/09 16:39:19 elharo Exp $
 */



package org.jaxen.util;

import java.util.AbstractList;

/**
 * A utility class that implements singleton lists
 * (to avoid dependency on JDK 1.3). Many operations 
 * including <code>add()</code> and <code>remove()</code> throw
 * UnsupportedOperationExceptions. 
 * 
 * @version 1.2b12
 * @author Attila Szegedi
 * 
 */
public class SingletonList extends AbstractList {
    
    private final Object element;
    
    /**
     * Creates a new singleton list. 
     * 
     * @param element the single member of the list
     */
    public SingletonList(Object element) {
        this.element = element;
    }
    
    /** 
     * Returns 1.
     * 
     * @return 1
     */
    public int size() {
        return 1;
    }

    /**
     * Returns the single element in the list.
     * 
     * @return the only element in the list
     * 
     * @throws IndexOutOfBoundsException if index is not 0
     * 
     */
    public Object get(int index) {
        if(index == 0) {
            return element;
        }
        throw new IndexOutOfBoundsException(index + " != 0");
    }
    
}