/*
* Copyright 1999-2015 dangdang.com.
* <p>
* 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.
* </p>
*/
package com.dangdang.ddframe.rdb.sharding.merger.pipeline.coupling.aggregation;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import java.util.List;
/**
* 比较聚合单元.
*
* @author gaohongtao
*/
@RequiredArgsConstructor
@Slf4j
public final class ComparableAggregationUnit implements AggregationUnit {
private final boolean asc;
private Comparable<?> result;
@SuppressWarnings("unchecked")
@Override
public void merge(final List<Comparable<?>> values) {
if (null == values || null == values.get(0)) {
return;
}
if (null == result) {
result = values.get(0);
log.trace("Comparable result: {}", result);
return;
}
int comparedValue = ((Comparable) values.get(0)).compareTo(result);
if (asc && comparedValue < 0 || !asc && comparedValue > 0) {
result = values.get(0);
log.trace("Comparable result: {}", result);
}
}
@Override
public Comparable<?> getResult() {
return result;
}
}