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/*
* Copyright (c) 2007 Israfil Consulting Services Corporation
* Copyright (c) 2007 Christian Edward Gruber
* All Rights Reserved
*
* This software is licensed under the Berkeley Standard Distribution license,
* (BSD license), as defined below:
*
* 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 the documentation
* and/or other materials provided with the distribution.
* 3. Neither the name of Israfil Consulting Services nor the names of its contributors
* may be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGE.
*
* $Id: ArraySet.java 76 2006-08-03 15:37:05Z cgruber $
*/
package net.israfil.foundation.collections;
import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Random;
/**
* An iterator that is constructed from a collection and returns the
* contents of the collection in random order. Note that this is
* an iterator over a copy of the collection, not the collection
* itself, so remove() is not supported, and underlying changes
* to the original collection will not be reflected in this iterator.
*
* @author <a href="mailto:cgruber@israfil.net">Christian Edward Gruber </a>
*/
public class RandomOrderIterator<E> implements Iterator<E> {
private transient List<E> _collection;
private transient Random _random = new SecureRandom();
private transient List<Integer> _indexes;
public RandomOrderIterator(Collection<E> collection) {
_collection = new ArrayList<E>(collection);
_indexes = new LinkedList<Integer>();
for (int i = 0; i < _collection.size();i++) {
_indexes.add(i); // populate index source.
}
}
public RandomOrderIterator(Collection<E> collection, Random random) {
this(collection);
this._random = random;
}
public boolean hasNext() {
return _indexes.size() > 0;
}
public E next() {
Integer index = _indexes.remove(_random.nextInt(_indexes.size()));
return _collection.get(index);
}
/**
* Because of the means required to track the current node,
* removing anything from the underlying collection is not supported.
*/
public void remove() {
throw new UnsupportedOperationException();
}
}
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