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Add LoopingIterator, from Jonathan Carlson 

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@130869 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Stephen Colebourne 2002-11-21 23:09:26 +00:00
parent af5dd4d71a
commit 9d123df763
3 changed files with 418 additions and 4 deletions
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166
src/java/org/apache/commons/collections/iterators/LoopingIterator.java Normal file
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/*
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/iterators/LoopingIterator.java,v 1.1 2002/11/21 23:09:01 scolebourne Exp $
* $Revision: 1.1 $
* $Date: 2002/11/21 23:09:01 $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 1999-2001 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
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Group.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 APACHE SOFTWARE FOUNDATION OR
* ITS 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.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
package org.apache.commons.collections.iterators;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* <code>LoopingIterator</code> provides an Iterator that restarts when it
* reaches the end.
* <p>
* The iterator will loop continuously around the provided elements, unless
* there are no elements in the collection to begin with, or all the elements
* are removed using the {@link remove} method.
* <p>
* Concurrent modifications are not directly supported, and for most collection
* implementations will throw a ConcurrentModificationException.
*
* @since 2.2
* @author <a href="mailto:joncrlsn@users.sf.net">Jonathan Carlson</a>
* @author Stephen Colebourne
* @version $Revision: 1.1 $
*/
public class LoopingIterator implements Iterator {
/** The collection to base the iterator on */
private Collection collection;
/** The current iterator */
private Iterator iterator;
/**
* Constructor that wraps a collection.
* <p>
* There is no way to reset an Iterator instance without recreating it from
* the original source, so the Collection must be passed in.
*
* @param coll the collection to wrap
* @throws NullPointerException if the collection is null
*/
public LoopingIterator(Collection coll) {
if (coll == null) {
throw new NullPointerException("The collection must not be null");
}
collection = coll;
reset();
}
/**
* Has the iterator any more elements.
* <p>
* Returns false only if the collection originally had zero elements, or
* all the elements have been removed using {@link #remove}.
*
* @return <code>true</code> if there are more elements
*/
public boolean hasNext() {
return (collection.size() > 0);
}
/**
* Returns the next object in the collection.
* <p>
* If at the end of the collection, return the first element.
*
* @throws NoSuchElementException if there are no elements
* at all. Use {@link #hasNext} to avoid this error.
*/
public Object next() {
if (collection.size() == 0) {
throw new NoSuchElementException("There are no elements for this iterator to loop on");
}
if (iterator.hasNext() == false) {
reset();
}
return iterator.next();
}
/**
* Removes the previously retrieved item from the underlying collection.
* <p>
* This feature is only supported if the underlying collection's
* {@link #iterator} method returns an implementation that supports it.
* <p>
* This method can only be called after at least one {@link #next} method call.
* After a removal, the remove method may not be called again until another
* next has been performed. If the {@link #reset} is called, then remove may
* not be called until {@link #next} is called again.
*/
public void remove() {
iterator.remove();
}
/**
* Resets the iterator back to the start of the collection.
*/
public void reset() {
iterator = collection.iterator();
}
/**
* Gets the size of the collection underlying the iterator.
*
* @return the current collection size
*/
public int size() {
return collection.size();
}
}

9
src/test/org/apache/commons/collections/iterators/TestAll.java
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@ -1,7 +1,7 @@
/*
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/test/org/apache/commons/collections/iterators/TestAll.java,v 1.2 2002/08/17 11:39:16 scolebourne Exp $
* $Revision: 1.2 $
* $Date: 2002/08/17 11:39:16 $
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/test/org/apache/commons/collections/iterators/TestAll.java,v 1.3 2002/11/21 23:09:26 scolebourne Exp $
* $Revision: 1.3 $
* $Date: 2002/11/21 23:09:26 $
*
* ====================================================================
*
@ -68,7 +68,7 @@ import junit.framework.TestSuite;
/**
* Entry point for all Collections tests.
* @author Rodney Waldhoff
* @version $Id: TestAll.java,v 1.2 2002/08/17 11:39:16 scolebourne Exp $
* @version $Id: TestAll.java,v 1.3 2002/11/21 23:09:26 scolebourne Exp $
*/
public class TestAll extends TestCase {
public TestAll(String testName) {
@ -84,6 +84,7 @@ public class TestAll extends TestCase {
suite.addTest(TestFilterListIterator.suite());
suite.addTest(TestIteratorChain.suite());
suite.addTest(TestListIteratorWrapper.suite());
suite.addTest(TestLoopingIterator.suite());
suite.addTest(TestSingletonIterator.suite());
suite.addTest(TestSingletonListIterator.suite());
suite.addTest(TestUniqueFilterIterator.suite());

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src/test/org/apache/commons/collections/iterators/TestLoopingIterator.java Normal file
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/*
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/test/org/apache/commons/collections/iterators/TestLoopingIterator.java,v 1.1 2002/11/21 23:09:26 scolebourne Exp $
* $Revision: 1.1 $
* $Date: 2002/11/21 23:09:26 $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 1999-2001 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
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Group.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 APACHE SOFTWARE FOUNDATION OR
* ITS 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.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
package org.apache.commons.collections.iterators;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.NoSuchElementException;
import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;
/**
* Tests the LoopingIterator class using jUnit.
*
* @author <a href="mailto:joncrlsn@users.sf.net">Jonathan Carlson</a>
* @author Stephen Colebourne
*/
public class TestLoopingIterator extends TestCase {
public TestLoopingIterator(String testName) {
super(testName);
}
public static Test suite() {
return new TestSuite(TestLoopingIterator.class);
}
/**
* Tests constructor exception.
*/
public void testConstructorEx() throws Exception {
try {
new LoopingIterator(null);
fail();
} catch (NullPointerException ex) {
}
}
/**
* Tests whether an empty looping iterator works as designed.
* @throws Exception If something unexpected occurs.
*/
public void testLooping0() throws Exception {
List list = new ArrayList();
LoopingIterator loop = new LoopingIterator(list);
assertTrue("hasNext should return false", loop.hasNext() == false);
try {
loop.next();
fail("NoSuchElementException was not thrown during next() call.");
} catch (NoSuchElementException ex) {
}
}
/**
* Tests whether a populated looping iterator works as designed.
* @throws Exception If something unexpected occurs.
*/
public void testLooping1() throws Exception {
List list = new ArrayList(Arrays.asList(new String[] { "a" }));
LoopingIterator loop = new LoopingIterator(list);
assertTrue("1st hasNext should return true", loop.hasNext());
assertEquals("a", loop.next());
assertTrue("2nd hasNext should return true", loop.hasNext());
assertEquals("a", loop.next());
assertTrue("3rd hasNext should return true", loop.hasNext());
assertEquals("a", loop.next());
}
/**
* Tests whether a populated looping iterator works as designed.
* @throws Exception If something unexpected occurs.
*/
public void testLooping2() throws Exception {
List list = new ArrayList(Arrays.asList(new String[] { "a", "b" }));
LoopingIterator loop = new LoopingIterator(list);
assertTrue("1st hasNext should return true", loop.hasNext());
assertEquals("a", loop.next());
assertTrue("2nd hasNext should return true", loop.hasNext());
assertEquals("b", loop.next());
assertTrue("3rd hasNext should return true", loop.hasNext());
assertEquals("a", loop.next());
}
/**
* Tests whether a populated looping iterator works as designed.
* @throws Exception If something unexpected occurs.
*/
public void testLooping3() throws Exception {
List list = new ArrayList(Arrays.asList(new String[] { "a", "b", "c" }));
LoopingIterator loop = new LoopingIterator(list);
assertTrue("1st hasNext should return true", loop.hasNext());
assertEquals("a", loop.next());
assertTrue("2nd hasNext should return true", loop.hasNext());
assertEquals("b", loop.next());
assertTrue("3rd hasNext should return true", loop.hasNext());
assertEquals("c", loop.next());
assertTrue("4th hasNext should return true", loop.hasNext());
assertEquals("a", loop.next());
}
/**
* Tests the remove() method on a LoopingIterator wrapped ArrayList.
* @throws Exception If something unexpected occurs.
*/
public void testRemoving1() throws Exception {
List list = new ArrayList(Arrays.asList(new String[] { "a", "b", "c" }));
LoopingIterator loop = new LoopingIterator(list);
assertEquals("list should have 3 elements.", 3, list.size());
assertTrue("1st hasNext should return true", loop.hasNext());
assertEquals("a", loop.next());
loop.remove(); // removes a
assertEquals("list should have 2 elements.", 2, list.size());
assertTrue("2nd hasNext should return true", loop.hasNext());
assertEquals("b", loop.next());
loop.remove(); // removes b
assertEquals("list should have 1 elements.", 1, list.size());
assertTrue("3rd hasNext should return true", loop.hasNext());
assertEquals("c", loop.next());
loop.remove(); // removes c
assertEquals("list should have 0 elements.", 0, list.size());
assertTrue("4th hasNext should return false", loop.hasNext() == false);
try {
loop.next();
fail("Expected NoSuchElementException to be thrown.");
} catch (NoSuchElementException ex) {
}
}
/**
* Tests the reset() method on a LoopingIterator wrapped ArrayList.
* @throws Exception If something unexpected occurs.
*/
public void testReset() throws Exception {
List list = new ArrayList(Arrays.asList(new String[] { "a", "b", "c" }));
LoopingIterator loop = new LoopingIterator(list);
assertEquals("a", loop.next());
assertEquals("b", loop.next());
loop.reset();
assertEquals("a", loop.next());
loop.reset();
assertEquals("a", loop.next());
assertEquals("b", loop.next());
assertEquals("c", loop.next());
loop.reset();
assertEquals("a", loop.next());
assertEquals("b", loop.next());
assertEquals("c", loop.next());
}
/**
* Tests the size() method on a LoopingIterator wrapped ArrayList.
* @throws Exception If something unexpected occurs.
*/
public void testSize() throws Exception {
List list = new ArrayList(Arrays.asList(new String[] { "a", "b", "c" }));
LoopingIterator loop = new LoopingIterator(list);
assertEquals(3, loop.size());
loop.next();
loop.next();
assertEquals(3, loop.size());
loop.reset();
assertEquals(3, loop.size());
loop.next();
loop.remove();
assertEquals(2, loop.size());
}
}