src/main/java/net/floodlightcontroller/util/MultiIterator.java

/**
*    Copyright 2012 Big Switch Networks, Inc. 
*    Originally created by David Erickson, Stanford University
* 
*    Licensed 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 net.floodlightcontroller.util;

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

/**
 * Iterator over all values in an iterator of iterators
 *
 * @param <T> the type of elements returned by this iterator
 */
public class MultiIterator<T> implements Iterator<T> {
    Iterator<Iterator<T>> subIterator;
    Iterator<T> current = null;
    
    public MultiIterator(Iterator<Iterator<T>> subIterator) {
        super();
        this.subIterator = subIterator;
    }

    @Override
    public boolean hasNext() {
        if (current == null) {
            if (subIterator.hasNext()) {
                current = subIterator.next();
            } else {
                return false;
            }
        }
        while (!current.hasNext() && subIterator.hasNext()) {
            current = subIterator.next();
        }
        
        return current.hasNext();
    }

    @Override
    public T next() {
        if (hasNext())
            return current.next();
        throw new NoSuchElementException();
    }

    @Override
    public void remove() {
        if (hasNext())
            current.remove();
        throw new NoSuchElementException();
    }
}