org.apache.flink.api.java.aggregation.MinAggregationFunction Maven / Gradle / Ivy
/*
* 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.api.java.aggregation;
public class MinAggregationFunction> extends AggregationFunction {
private static final long serialVersionUID = 1L;
private T value;
@Override
public void initializeAggregate() {
value = null;
}
@Override
public void aggregate(T val) {
if (value != null) {
int cmp = value.compareTo(val);
value = (cmp < 0) ? value : val;
} else {
value = val;
}
}
@Override
public T getAggregate() {
return value;
}
@Override
public String toString() {
return "MIN";
}
// --------------------------------------------------------------------------------------------
public static final class MinAggregationFunctionFactory implements AggregationFunctionFactory {
private static final long serialVersionUID = 1L;
@SuppressWarnings({ "unchecked", "rawtypes" })
@Override
public AggregationFunction createAggregationFunction(Class type) {
if (Comparable.class.isAssignableFrom(type)) {
return (AggregationFunction) new MinAggregationFunction();
} else {
throw new UnsupportedAggregationTypeException("The type " + type.getName() +
" is not supported for minimum aggregation. " +
"Minimum aggregatable types must implement the Comparable interface.");
}
}
}
}