Enumerator.java

/*
 * Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * 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.springframework.security.web.savedrequest;

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

/**
 * <p>
 * Adapter that wraps an <code>Enumeration</code> around a Java 2 collection
 * <code>Iterator</code>.
 * </p>
 * <p>
 * Constructors are provided to easily create such wrappers.
 * </p>
 * <p>
 * This class is based on code in Apache Tomcat.
 * </p>
 *
 * @author Craig McClanahan
 * @author Andrey Grebnev
 */
public class Enumerator<T> implements Enumeration<T> {
	// ~ Instance fields
	// ================================================================================================

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

	// ~ Constructors
	// ===================================================================================================

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

		if (!clone) {
			this.iterator = iterator;
		}
		else {
			List<T> list = new ArrayList<T>();

			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<?, T> 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<?, T> map, boolean clone) {
		this(map.values().iterator(), clone);
	}

	// ~ 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 T nextElement() throws NoSuchElementException {
		return (iterator.next());
	}
}