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Add IteratorUtils unmodifiable iterators, from Rich Dougherty 

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@130885 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Stephen Colebourne 2002-12-08 15:42:35 +00:00
parent 257fbcc0a5
commit ba27ecd2d4
2 changed files with 325 additions and 8 deletions
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140
src/java/org/apache/commons/collections/IteratorUtils.java
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@ -1,7 +1,7 @@
/*
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/IteratorUtils.java,v 1.5 2002/11/21 23:08:27 scolebourne Exp $
* $Revision: 1.5 $
* $Date: 2002/11/21 23:08:27 $
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/IteratorUtils.java,v 1.6 2002/12/08 15:42:35 scolebourne Exp $
* $Revision: 1.6 $
* $Date: 2002/12/08 15:42:35 $
*
* ====================================================================
*
@ -60,6 +60,7 @@
*/
package org.apache.commons.collections;
import java.io.Serializable;
import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.util.ArrayList;
@ -91,7 +92,7 @@ import org.apache.commons.collections.iterators.TransformIterator;
* <code>org.apache.commons.collections.iterators</code> subpackage.
*
* @author <a href="mailto:scolebourne@joda.org">Stephen Colebourne</a>
* @version $Id: IteratorUtils.java,v 1.5 2002/11/21 23:08:27 scolebourne Exp $
* @version $Id: IteratorUtils.java,v 1.6 2002/12/08 15:42:35 scolebourne Exp $
* @since 2.1
*/
public class IteratorUtils {
@ -113,6 +114,9 @@ public class IteratorUtils {
private IteratorUtils() {
}
// Iterator creators
//----------------------------------------------------------------------
/**
* Gets an empty iterator.
* <p>
@ -238,6 +242,34 @@ public class IteratorUtils {
// public static ListIterator arrayListIterator(Object[] array, int start, int end) {
// return new ArrayListIterator(array, start, end);
// }
// Iterator wrappers
//----------------------------------------------------------------------
/**
* Gets an immutable version of an {@link Iterator}. The returned object
* will always throw an {@link java.lang.UnsupportedOperationException} for
* the {@link Iterator#remove()} method.
*
* @param iterator The iterator to make immutable.
* @return An immutable version of the iterator.
*/
public static Iterator unmodifiableIterator(Iterator iterator) {
return new UnmodifiableIterator(iterator);
}
/**
* Gets an immutable version of a {@link ListIterator}.The returned object
* will always throw an {@link java.lang.UnsupportedOperationException} for
* the {@link Iterator#remove()}, {@link ListIterator#add()} and
* {@link ListIterator#set(Object)} methods.
*
* @param listIterator The iterator to make immutable.
* @return An immutable version of the iterator.
*/
public static ListIterator unmodifiableListIterator(ListIterator listIterator) {
return new UnmodifiableListIterator(listIterator);
}
/**
* Gets an iterator that iterates through two {@link Iterator}s
@ -685,5 +717,103 @@ public class IteratorUtils {
}
}
/**
* A wrapper for an {@link java.util.Iterator} which makes it immutable. All
* calls are passed through to the delegate. The {@link #remove()} method
* always throws an {@link java.lang.UnsupportedOperationException}.
*
* @author <a href="mailto:rich@rd.gen.nz">Rich Dougherty</a>
*/
static class UnmodifiableIterator implements Iterator, Serializable {
/**
* All calls to this iterator are passed to the delegate.
*/
protected Iterator delegate;
/**
* Create an UnmodifiableIterator.
*
* @param delegate The delegate to pass all calls to.
*/
public UnmodifiableIterator(Iterator delegate) {
this.delegate = delegate;
}
public boolean hasNext() {
return delegate.hasNext();
}
public Object next() {
return delegate.next();
}
public void remove() {
throw new UnsupportedOperationException("This iterator is immutable");
}
}
/**
* A wrapper for an {@link java.util.ListIterator} which makes it immutable.
* All calls are passed through to the delegate. The {@link #remove()},
* {@link #add(Object)} and (@link #set(Object)} methods always throw an
* {@link java.lang.UnsupportedOperationException}.
*
* @author <a href="mailto:rich@rd.gen.nz">Rich Dougherty</a>
*/
static class UnmodifiableListIterator
implements ListIterator, Serializable {
/**
* All calls to this iterator are passed to the delegate.
*/
protected ListIterator delegate;
/**
* Create an UnmodifiableListIterator.
*
* @param delegate The delegate to pass all calls to.
*/
public UnmodifiableListIterator(ListIterator delegate) {
this.delegate = delegate;
}
public boolean hasNext() {
return delegate.hasNext();
}
public Object next() {
return delegate.next();
}
public boolean hasPrevious() {
return delegate.hasPrevious();
}
public Object previous() {
return delegate.previous();
}
public int nextIndex() {
return delegate.nextIndex();
}
public int previousIndex() {
return delegate.previousIndex();
}
public void remove() {
throw new UnsupportedOperationException("This iterator is immutable");
}
public void set(Object o) {
throw new UnsupportedOperationException("This iterator is immutable");
}
public void add(Object o) {
throw new UnsupportedOperationException("This iterator is immutable");
}
}
}

193
src/test/org/apache/commons/collections/TestIteratorUtils.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/TestIteratorUtils.java,v 1.2 2002/10/12 22:36:21 scolebourne Exp $
* $Revision: 1.2 $
* $Date: 2002/10/12 22:36:21 $
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/test/org/apache/commons/collections/TestIteratorUtils.java,v 1.3 2002/12/08 15:42:35 scolebourne Exp $
* $Revision: 1.3 $
* $Date: 2002/12/08 15:42:35 $
*
* ====================================================================
*
@ -62,7 +62,9 @@ package org.apache.commons.collections;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import junit.framework.Test;
/**
@ -74,6 +76,9 @@ public class TestIteratorUtils extends BulkTest {
super(name);
}
public static void main(String args[]) {
junit.textui.TestRunner.run(suite());
}
public static Test suite() {
return BulkTest.makeSuite(TestIteratorUtils.class);
@ -106,4 +111,186 @@ public class TestIteratorUtils extends BulkTest {
assertEquals(list, Arrays.asList(result));
}
/**
* Gets an immutable Iterator operating on the elements ["a", "b", "c", "d"].
*/
private Iterator getImmutableIterator() {
List list = new ArrayList();
list.add("a");
list.add("b");
list.add("c");
list.add("d");
return IteratorUtils.unmodifiableIterator(list.iterator());
}
/**
* Gets an immutable ListIterator operating on the elements ["a", "b", "c", "d"].
*/
private ListIterator getImmutableListIterator() {
List list = new ArrayList();
list.add("a");
list.add("b");
list.add("c");
list.add("d");
return IteratorUtils.unmodifiableListIterator(list.listIterator());
}
/**
* Test next() and hasNext() for an immutable Iterator.
*/
public void testUnmodifiableIteratorIteration() {
Iterator iterator = getImmutableIterator();
assertTrue(iterator.hasNext());
assertEquals("a", iterator.next());
assertTrue(iterator.hasNext());
assertEquals("b", iterator.next());
assertTrue(iterator.hasNext());
assertEquals("c", iterator.next());
assertTrue(iterator.hasNext());
assertEquals("d", iterator.next());
assertTrue(!iterator.hasNext());
}
/**
* Test next(), hasNext(), previous() and hasPrevious() for an immutable
* ListIterator.
*/
public void testUnmodifiableListIteratorIteration() {
ListIterator listIterator = getImmutableListIterator();
assertTrue(!listIterator.hasPrevious());
assertTrue(listIterator.hasNext());
assertEquals("a", listIterator.next());
assertTrue(listIterator.hasPrevious());
assertTrue(listIterator.hasNext());
assertEquals("b", listIterator.next());
assertTrue(listIterator.hasPrevious());
assertTrue(listIterator.hasNext());
assertEquals("c", listIterator.next());
assertTrue(listIterator.hasPrevious());
assertTrue(listIterator.hasNext());
assertEquals("d", listIterator.next());
assertTrue(listIterator.hasPrevious());
assertTrue(!listIterator.hasNext());
assertEquals("d", listIterator.previous());
assertTrue(listIterator.hasPrevious());
assertTrue(listIterator.hasNext());
assertEquals("c", listIterator.previous());
assertTrue(listIterator.hasPrevious());
assertTrue(listIterator.hasNext());
assertEquals("b", listIterator.previous());
assertTrue(listIterator.hasPrevious());
assertTrue(listIterator.hasNext());
assertEquals("a", listIterator.previous());
assertTrue(!listIterator.hasPrevious());
assertTrue(listIterator.hasNext());
}
/**
* Test remove() for an immutable Iterator.
*/
public void testUnmodifiableIteratorImmutability() {
Iterator iterator = getImmutableIterator();
try {
iterator.remove();
// We shouldn't get to here.
fail("remove() should throw an UnsupportedOperationException");
} catch (UnsupportedOperationException e) {
// This is correct; ignore the exception.
}
iterator.next();
try {
iterator.remove();
// We shouldn't get to here.
fail("remove() should throw an UnsupportedOperationException");
} catch (UnsupportedOperationException e) {
// This is correct; ignore the exception.
}
}
/**
* Test remove() for an immutable ListIterator.
*/
public void testUnmodifiableListIteratorImmutability() {
ListIterator listIterator = getImmutableListIterator();
try {
listIterator.remove();
// We shouldn't get to here.
fail("remove() should throw an UnsupportedOperationException");
} catch (UnsupportedOperationException e) {
// This is correct; ignore the exception.
}
try {
listIterator.set("a");
// We shouldn't get to here.
fail("set(Object) should throw an UnsupportedOperationException");
} catch (UnsupportedOperationException e) {
// This is correct; ignore the exception.
}
try {
listIterator.add("a");
// We shouldn't get to here.
fail("add(Object) should throw an UnsupportedOperationException");
} catch (UnsupportedOperationException e) {
// This is correct; ignore the exception.
}
listIterator.next();
try {
listIterator.remove();
// We shouldn't get to here.
fail("remove() should throw an UnsupportedOperationException");
} catch (UnsupportedOperationException e) {
// This is correct; ignore the exception.
}
try {
listIterator.set("a");
// We shouldn't get to here.
fail("set(Object) should throw an UnsupportedOperationException");
} catch (UnsupportedOperationException e) {
// This is correct; ignore the exception.
}
try {
listIterator.add("a");
// We shouldn't get to here.
fail("add(Object) should throw an UnsupportedOperationException");
} catch (UnsupportedOperationException e) {
// This is correct; ignore the exception.
}
}
}