org.redisson.misc.CompositeIterator Maven / Gradle / Ivy

/**
 * Copyright 2018 Nikita Koksharov
 *
 * 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 org.redisson.misc;

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

/**
 * @author Pepe Lu
 */
public class CompositeIterator implements Iterator {

	private Iterator> listIterator;
	private Iterator currentIterator;

	public CompositeIterator(Iterator> iterators) {
		listIterator = iterators;
	}

	@Override
	public boolean hasNext() {
		if (currentIterator == null || !currentIterator.hasNext()) {
			while (listIterator.hasNext()) {
				Iterator iterator = listIterator.next();
				currentIterator = iterator;
				if (iterator.hasNext()) {
					return true;
				}
			}
			return false;
		}

		return currentIterator.hasNext();
	}

	@Override
	public T next() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}

		return currentIterator.next();
	}

	@Override
	public void remove() {
		if (currentIterator == null) {
			throw new IllegalStateException("next() has not yet been called");
		}

		currentIterator.remove();
	}
}