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Commons Collections example source code file (UnmodifiableIterator.java)

This example Commons Collections source code file (UnmodifiableIterator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Collections tags/keywords

illegalargumentexception, iterator, iterator, object, object, unmodifiable, unmodifiable, unmodifiableiterator, unmodifiableiterator, unsupportedoperationexception, util

The Commons Collections UnmodifiableIterator.java source code

/*
 *  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.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: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 * 
 * @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.
     * <p>
     * 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");
    }

}

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