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Types that extend and augment the Java Collections Framework.
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/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2004 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
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 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
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 * SUCH DAMAGE.
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 */
package org.apache.commons.collections.iterators;

import java.util.Iterator;

import org.apache.commons.collections.Unmodifiable;

/** 
 * Decorates an iterator such that it cannot be modified.
 *
 * @since Commons Collections 3.0
 * @version $Revision: 1.4 $ $Date: 2004/01/14 21:43:14 $
 * 
 * @author Stephen Colebourne
 */
public final class UnmodifiableIterator implements Iterator, Unmodifiable {

    /** The iterator being decorated */
    private Iterator iterator;

    //-----------------------------------------------------------------------
    /**
     * Decorates the specified iterator such that it cannot be modified.
     * 
     * If the iterator is already unmodifiable it is returned directly.
     *
     * @param iterator  the iterator to decorate
     * @throws IllegalArgumentException if the iterator is null
     */
    public static Iterator decorate(Iterator iterator) {
        if (iterator == null) {
            throw new IllegalArgumentException("Iterator must not be null");
        }
        if (iterator instanceof Unmodifiable) {
            return iterator;
        }
        return new UnmodifiableIterator(iterator);
    }
    
    //-----------------------------------------------------------------------
    /**
     * Constructor.
     *
     * @param iterator  the iterator to decorate
     */
    private UnmodifiableIterator(Iterator iterator) {
        super();
        this.iterator = iterator;
    }

    //-----------------------------------------------------------------------
    public boolean hasNext() {
        return iterator.hasNext();
    }

    public Object next() {
        return iterator.next();
    }

    public void remove() {
        throw new UnsupportedOperationException("remove() is not supported");
    }

}