container/catalina/src/share/org/apache/catalina/util/Enumerator.java

/*
 * Copyright 1999,2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.apache.catalina.util;


import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.util.NoSuchElementException;


/**
 * Adapter class that wraps an <code>Enumeration</code> around a Java2
 * collection classes object <code>Iterator</code> so that existing APIs
 * returning Enumerations can easily run on top of the new collections.
 * Constructors are provided to easliy create such wrappers.
 *
 * @author Craig R. McClanahan
 * @version $Revision$ $Date$
 */

public final class Enumerator implements Enumeration {


    // ----------------------------------------------------------- Constructors


    /**
     * Return an Enumeration over the values of the specified Collection.
     *
     * @param collection Collection whose values should be enumerated
     */
    public Enumerator(Collection collection) {

        this(collection.iterator());

    }


    /**
     * Return an Enumeration over the values of the specified Collection.
     *
     * @param collection Collection whose values should be enumerated
     * @param clone true to clone iterator
     */
    public Enumerator(Collection collection, boolean clone) {

        this(collection.iterator(), clone);

    }


    /**
     * Return an Enumeration over the values returned by the
     * specified Iterator.
     *
     * @param iterator Iterator to be wrapped
     */
    public Enumerator(Iterator iterator) {

        super();
        this.iterator = iterator;

    }


    /**
     * Return an Enumeration over the values returned by the
     * specified Iterator.
     *
     * @param iterator Iterator to be wrapped
     * @param clone true to clone iterator
     */
    public Enumerator(Iterator iterator, boolean clone) {

        super();
        if (!clone) {
            this.iterator = iterator;
        } else {
            List list = new ArrayList();
            while (iterator.hasNext()) {
                list.add(iterator.next());
            }
            this.iterator = list.iterator();   
        }

    }


    /**
     * Return an Enumeration over the values of the specified Map.
     *
     * @param map Map whose values should be enumerated
     */
    public Enumerator(Map map) {

        this(map.values().iterator());

    }


    /**
     * Return an Enumeration over the values of the specified Map.
     *
     * @param map Map whose values should be enumerated
     * @param clone true to clone iterator
     */
    public Enumerator(Map map, boolean clone) {

        this(map.values().iterator(), clone);

    }


    // ----------------------------------------------------- Instance Variables


    /**
     * The <code>Iterator</code> over which the <code>Enumeration</code>
     * represented by this class actually operates.
     */
    private Iterator iterator = null;


    // --------------------------------------------------------- Public Methods


    /**
     * Tests if this enumeration contains more elements.
     *
     * @return <code>true</code> if and only if this enumeration object
     *  contains at least one more element to provide, <code>false</code>
     *  otherwise
     */
    public boolean hasMoreElements() {

        return (iterator.hasNext());

    }


    /**
     * Returns the next element of this enumeration if this enumeration
     * has at least one more element to provide.
     *
     * @return the next element of this enumeration
     *
     * @exception NoSuchElementException if no more elements exist
     */
    public Object nextElement() throws NoSuchElementException {

        return (iterator.next());

    }


}