// GenericsNote: Converted.
/*
 *  Copyright 2003-2004 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.commons.collections15.collection;

import java.util.Collection;
import java.util.Iterator;

import org.apache.commons.collections15.Unmodifiable;
import org.apache.commons.collections15.iterators.UnmodifiableIterator;

/**
 * Decorates another <code>Collection</code> to ensure it can't be altered.
 * <p/>
 * This class is Serializable from Commons Collections 3.1.
 *
 * @author Matt Hall, John Watkinson, Stephen Colebourne
 * @version $Revision: 1.1 $ $Date: 2005/10/11 17:05:20 $
 * @since Commons Collections 3.0
 */
public final class UnmodifiableCollection<E> extends
		AbstractSerializableCollectionDecorator<E> implements Unmodifiable {

	/**
	 * Serialization version
	 */
	private static final long serialVersionUID = -239892006883819945L;

	/**
	 * Factory method to create an unmodifiable collection.
	 * <p/>
	 * If the collection passed in is already unmodifiable, it is returned.
	 *
	 * @param coll
	 *            the collection to decorate, must not be null
	 * @return an unmodifiable collection
	 * @throws IllegalArgumentException
	 *             if collection is null
	 */
	public static <E> Collection<E> decorate(Collection<E> coll) {
		if (coll instanceof Unmodifiable) {
			return coll;
		}
		return new UnmodifiableCollection<E>(coll);
	}

	// -----------------------------------------------------------------------
	/**
	 * Constructor that wraps (not copies).
	 *
	 * @param coll
	 *            the collection to decorate, must not be null
	 * @throws IllegalArgumentException
	 *             if collection is null
	 */
	private UnmodifiableCollection(Collection<E> coll) {
		super(coll);
	}

	// -----------------------------------------------------------------------
	@Override
	public Iterator<E> iterator() {
		return UnmodifiableIterator.decorate(getCollection().iterator());
	}

	@Override
	public boolean add(E object) {
		throw new UnsupportedOperationException();
	}

	@Override
	public boolean addAll(Collection<? extends E> coll) {
		throw new UnsupportedOperationException();
	}

	@Override
	public void clear() {
		throw new UnsupportedOperationException();
	}

	@Override
	public boolean remove(Object object) {
		throw new UnsupportedOperationException();
	}

	@Override
	public boolean removeAll(Collection<?> coll) {
		throw new UnsupportedOperationException();
	}

	@Override
	public boolean retainAll(Collection<?> coll) {
		throw new UnsupportedOperationException();
	}

}