org.apache.jackrabbit.commons.iterator.FilterIterator Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with this
* work for additional information regarding copyright ownership. The ASF
* licenses this file to You under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package org.apache.jackrabbit.commons.iterator;
import org.apache.jackrabbit.commons.predicate.Predicate;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* Iterator filtering out items which do not match a given predicate.
* @param
*/
public class FilterIterator implements Iterator {
private final Iterator iterator;
private final Predicate predicate;
private T next = null;
/**
* Create a new filtered iterator based on the given iterator.
*
* @param iterator iterator to filter
* @param predicate only item matching this predicate are included
*/
public FilterIterator(Iterator iterator, Predicate predicate) {
super();
this.iterator = iterator;
this.predicate = predicate;
}
public boolean hasNext() {
while (next == null && iterator.hasNext()) {
T e = iterator.next();
if (predicate.evaluate(e)) {
next = e;
}
}
return next != null;
}
public T next() {
if (hasNext()) {
T e = next;
next = null;
return e;
}
else {
throw new NoSuchElementException();
}
}
/**
* @throws UnsupportedOperationException always
* @see java.util.Iterator#remove()
*/
public void remove() {
throw new UnsupportedOperationException();
}
}