CollectionUtilities.java

/*
 * GNU LESSER GENERAL PUBLIC LICENSE Copyright (C) 2006 The Lobo Project
 * 
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 * 
 * This library 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 Lesser General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 * 
 * Contact info: lobochief@users.sourceforge.net
 */
/*
 * Created on Jun 9, 2005
 */
package com.nvarghese.beowulf.common.cobra.util;

import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.NoSuchElementException;

/**
 * @author J. H. S.
 */
public class CollectionUtilities {

	/**
	 * 
	 */
	private CollectionUtilities() {

		super();
	}

	public static Enumeration getIteratorEnumeration(final Iterator i) {

		return new Enumeration() {

			public boolean hasMoreElements() {

				return i.hasNext();
			}

			public Object nextElement() {

				return i.next();
			}
		};
	}

	public static Iterator iteratorUnion(final Iterator[] iterators) {

		return new Iterator() {

			private int iteratorIndex = 0;
			private Iterator current = iterators.length > 0 ? iterators[0] : null;

			public boolean hasNext() {

				for (;;) {
					if (current == null) {
						return false;
					}
					if (current.hasNext()) {
						return true;
					}
					iteratorIndex++;
					current = iteratorIndex >= iterators.length ? null : iterators[iteratorIndex];
				}
			}

			public Object next() {

				for (;;) {
					if (this.current == null) {
						throw new NoSuchElementException();
					}
					try {
						return this.current.next();
					} catch (NoSuchElementException nse) {
						this.iteratorIndex++;
						this.current = this.iteratorIndex >= iterators.length ? null : iterators[this.iteratorIndex];
					}
				}
			}

			public void remove() {

				if (this.current == null) {
					throw new NoSuchElementException();
				}
				this.current.remove();
			}
		};
	}

	public static Collection reverse(Collection collection) {

		LinkedList newCollection = new LinkedList();
		Iterator i = collection.iterator();
		while (i.hasNext()) {
			newCollection.addFirst(i.next());
		}
		return newCollection;
	}

	public static Iterator singletonIterator(final Object item) {

		return new Iterator() {

			private boolean gotItem = false;

			public boolean hasNext() {

				return !this.gotItem;
			}

			public Object next() {

				if (this.gotItem) {
					throw new NoSuchElementException();
				}
				this.gotItem = true;
				return item;
			}

			public void remove() {

				if (!this.gotItem) {
					this.gotItem = true;
				} else {
					throw new NoSuchElementException();
				}
			}
		};
	}
}