trunk/chemistry-opencmis-server/chemistry-opencmis-server-jcr/src/main/java/org/apache/chemistry/opencmis/jcr/util/FilterIterator.java

/*
 * 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.chemistry.opencmis.jcr.util;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * Iterator filtering out items which do not match a given predicate.
 * 
 * @param <T>
 */
public class FilterIterator<T> implements Iterator<T> {
    private final Iterator<T> iterator;
    private final Predicate<T> predicate;

    private T next;

    /**
     * Create a new filtered iterator based on the given <code>iterator</code>.
     * 
     * @param iterator
     *            iterator to filter
     * @param predicate
     *            only item matching this predicate are included
     */
    public FilterIterator(Iterator<T> iterator, Predicate<T> predicate) {
        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();
        }
    }

    public void remove() {
        throw new UnsupportedOperationException();
    }

}