diff options
Diffstat (limited to 'israfil-foundation-collections/src/main/java/net/israfil/foundation/collections/RandomOrderIterator.java')
| -rw-r--r-- | israfil-foundation-collections/src/main/java/net/israfil/foundation/collections/RandomOrderIterator.java | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/israfil-foundation-collections/src/main/java/net/israfil/foundation/collections/RandomOrderIterator.java b/israfil-foundation-collections/src/main/java/net/israfil/foundation/collections/RandomOrderIterator.java new file mode 100644 index 0000000..8b97e4a --- /dev/null +++ b/israfil-foundation-collections/src/main/java/net/israfil/foundation/collections/RandomOrderIterator.java @@ -0,0 +1,94 @@ +/*
+ * 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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