/*
* $Header: /home/cvs/jakarta-commons/collections/src/java/org/apache/commons/collections/iterators/FilterListIterator.java,v 1.1 2002/08/15 23:13:51 pjack Exp $
* $Revision: 1.1 $
* $Date: 2002/08/15 23:13:51 $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 1999-2002 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.ListIterator;
import java.util.NoSuchElementException;
import org.apache.commons.collections.Predicate;
/**
* A proxy {@link ListIterator ListIterator} which
* takes a {@link Predicate Predicate} instance to filter
* out objects from an underlying <code>ListIterator</code>
* instance. Only objects for which the specified
* <code>Predicate</code> evaluates to <code>true</code> are
* returned by the iterator.
*
* @since 2.0
* @version $Revision: 1.1 $ $Date: 2002/08/15 23:13:51 $
* @author Rodney Waldhoff
*/
public class FilterListIterator extends ProxyListIterator {
// Constructors
//-------------------------------------------------------------------------
/**
* Constructs a new <Code>FilterListIterator</Code> that will not
* function until
* {@link ProxyListIterator#setListIterator(ListIterator) setListIterator}
* and {@link #setPredicate(Predicate) setPredicate} are invoked.
*/
public FilterListIterator() {
}
/**
* Constructs a new <Code>FilterListIterator</Code> that will not
* function until {@link #setPredicate(Predicate) setPredicate} is invoked.
*
* @param iterator the iterator to use
*/
public FilterListIterator(ListIterator iterator ) {
super(iterator);
}
/**
* Constructs a new <Code>FilterListIterator</Code>.
*
* @param iterator the iterator to use
* @param predicate the predicate to use
*/
public FilterListIterator(ListIterator iterator, Predicate predicate) {
super(iterator);
this.predicate = predicate;
}
/**
* Constructs a new <Code>FilterListIterator</Code> that will not
* function until
* {@link ProxyListIterator#setListIterator(ListIterator) setListIterator}
* is invoked.
*
* @param predicate the predicate to use.
*/
public FilterListIterator(Predicate predicate) {
this.predicate = predicate;
}
// ListIterator interface
//-------------------------------------------------------------------------
/** Not supported. */
public void add(Object o) {
throw new UnsupportedOperationException("FilterListIterator.add(Object) is not supported.");
}
public boolean hasNext() {
if(nextObjectSet) {
return true;
} else {
return setNextObject();
}
}
public boolean hasPrevious() {
if(previousObjectSet) {
return true;
} else {
return setPreviousObject();
}
}
public Object next() {
if(!nextObjectSet) {
if(!setNextObject()) {
throw new NoSuchElementException();
}
}
nextIndex++;
Object temp = nextObject;
clearNextObject();
return temp;
}
public int nextIndex() {
return nextIndex;
}
public Object previous() {
if(!previousObjectSet) {
if(!setPreviousObject()) {
throw new NoSuchElementException();
}
}
nextIndex--;
Object temp = previousObject;
clearPreviousObject();
return temp;
}
public int previousIndex() {
return (nextIndex-1);
}
/** Not supported. */
public void remove() {
throw new UnsupportedOperationException("FilterListIterator.remove() is not supported.");
}
/** Not supported. */
public void set(Object o) {
throw new UnsupportedOperationException("FilterListIterator.set(Object) is not supported.");
}
// Properties
//-------------------------------------------------------------------------
/**
* Getter for the predicate property.
* @return value of the predicate property.
*/
public Predicate getPredicate() {
return predicate;
}
/**
* Setter for the predicate property.
* @param predicate new value for the predicate property.
*/
public void setPredicate(Predicate predicate) {
this.predicate = predicate;
}
// Private Methods
//-------------------------------------------------------------------------
private void clearNextObject() {
nextObject = null;
nextObjectSet = false;
}
private boolean setNextObject() {
ListIterator iterator = getListIterator();
Predicate predicate = getPredicate();
// if previousObjectSet,
// then we've walked back one step in the
// underlying list (due to a hasPrevious() call)
// so skip ahead one matching object
if(previousObjectSet) {
clearPreviousObject();
if(!setNextObject()) {
return false;
} else {
clearNextObject();
}
}
while(iterator.hasNext()) {
Object object = iterator.next();
if(predicate.evaluate(object)) {
nextObject = object;
nextObjectSet = true;
return true;
}
}
return false;
}
private void clearPreviousObject() {
previousObject = null;
previousObjectSet = false;
}
private boolean setPreviousObject() {
ListIterator iterator = getListIterator();
Predicate predicate = getPredicate();
// if nextObjectSet,
// then we've walked back one step in the
// underlying list (due to a hasNext() call)
// so skip ahead one matching object
if(nextObjectSet) {
clearNextObject();
if(!setPreviousObject()) {
return false;
} else {
clearPreviousObject();
}
}
while(iterator.hasPrevious()) {
Object object = iterator.previous();
if(predicate.evaluate(object)) {
previousObject = object;
previousObjectSet = true;
return true;
}
}
return false;
}
// Attributes
//-------------------------------------------------------------------------
/** Holds value of property "predicate". */
private Predicate predicate;
/**
* The value of the next (matching) object, when
* {@link #nextObjectSet} is true.
*/
private Object nextObject;
/**
* Whether or not the {@link #nextObject} has been set
* (possibly to <code>null</code>).
*/
private boolean nextObjectSet = false;
/**
* The value of the previous (matching) object, when
* {@link #previousObjectSet} is true.
*/
private Object previousObject;
/**
* Whether or not the {@link #previousObject} has been set
* (possibly to <code>null</code>).
*/
private boolean previousObjectSet = false;
/**
* The index of the element that would be returned by {@link #next}.
*/
private int nextIndex = 0;
}