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Types that extend and augment the Java Collections Framework.
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/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.collections.set;

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

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

/**
 * Decorates another Set to ensure it can't be altered.
 * 
 * This class is Serializable from Commons Collections 3.1.
 *
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
 * 
 * @author Stephen Colebourne
 */
public final class UnmodifiableSet
        extends AbstractSerializableSetDecorator
        implements Unmodifiable {

    /** Serialization version */
    private static final long serialVersionUID = 6499119872185240161L;

    /**
     * Factory method to create an unmodifiable set.
     * 
     * @param set  the set to decorate, must not be null
     * @throws IllegalArgumentException if set is null
     */
    public static Set decorate(Set set) {
        if (set instanceof Unmodifiable) {
            return set;
        }
        return new UnmodifiableSet(set);
    }

    //-----------------------------------------------------------------------
    /**
     * Constructor that wraps (not copies).
     * 
     * @param set  the set to decorate, must not be null
     * @throws IllegalArgumentException if set is null
     */
    private UnmodifiableSet(Set set) {
        super(set);
    }

    //-----------------------------------------------------------------------
    public Iterator iterator() {
        return UnmodifiableIterator.decorate(getCollection().iterator());
    }

    public boolean add(Object object) {
        throw new UnsupportedOperationException();
    }

    public boolean addAll(Collection coll) {
        throw new UnsupportedOperationException();
    }

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

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

    public boolean removeAll(Collection coll) {
        throw new UnsupportedOperationException();
    }

    public boolean retainAll(Collection coll) {
        throw new UnsupportedOperationException();
    }

}