/*
* 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.flink.runtime.operators.testutils;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.apache.flink.util.MutableObjectIterator;
/**
* An iterator that returns the union of a given set of iterators.
*/
public class UnionIterator<E> implements MutableObjectIterator<E> {
private MutableObjectIterator<E> currentSource;
private List<MutableObjectIterator<E>> nextSources;
public UnionIterator(MutableObjectIterator<E>... iterators) {
this(new ArrayList<MutableObjectIterator<E>>(Arrays.asList(iterators)));
}
public UnionIterator(List<MutableObjectIterator<E>> sources) {
this.currentSource = sources.remove(0);
this.nextSources = sources;
}
@Override
public E next(E target) throws IOException
{
E targetStaging = this.currentSource.next(target);
if (targetStaging != null) {
return targetStaging;
} else {
if (this.nextSources.size() > 0) {
this.currentSource = this.nextSources.remove(0);
return next(target);
}
else {
return null;
}
}
}
@Override
public E next() throws IOException
{
E targetStaging = this.currentSource.next();
if (targetStaging != null) {
return targetStaging;
} else {
if (this.nextSources.size() > 0) {
this.currentSource = this.nextSources.remove(0);
return next();
}
else {
return null;
}
}
}
}