eu.stratosphere.api.java.functions.FlatMapIterator Maven / Gradle / Ivy
/***********************************************************************************************************************
*
* Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
*
* 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 eu.stratosphere.api.java.functions;
import java.util.Iterator;
import eu.stratosphere.util.Collector;
/**
* A variant of the {@link FlatMapFunction} that returns elements through an iterator, rather then
* through a collector. In all other respects, it behaves exactly like the FlatMapFunction.
*
* The function needs to be serializable, as defined in {@link java.io.Serializable}.
*
* @param Type of the input elements.
* @param Type of the returned elements.
*/
public abstract class FlatMapIterator extends FlatMapFunction {
private static final long serialVersionUID = 1L;
/**
* The core method of the function. Takes an element from the input data set and transforms
* it into zero, one, or more elements.
*
* @param value The input value.
* @return An iterator over the returned elements.
*
* @throws Exception This method may throw exceptions. Throwing an exception will cause the operation
* to fail and may trigger recovery.
*/
public abstract Iterator flatMap(IN value) throws Exception;
// --------------------------------------------------------------------------------------------
/**
* Delegates calls to the {@link #flatMap(Object)} method.
*/
@Override
public final void flatMap(IN value, Collector out) throws Exception {
for (Iterator iter = flatMap(value); iter.hasNext(); ) {
out.collect(iter.next());
}
}
}