001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.functor.aggregator.functions; 018 019import java.util.List; 020 021import org.apache.commons.functor.Function; 022 023/** 024 * Aggregator function to be used with subclasses of 025 * {@link org.apache.commons.functor.aggregator.AbstractListBackedAggregator} 026 * which finds the maximum number in a list. It does this by traversing the list 027 * (once) -- so the complexity of this will be <i>O(n)</i>. 028 */ 029public class DoubleMaxAggregatorFunction implements Function<List<Double>, Double> { 030 /** 031 * Does the actual traversal of the list and finds the maximum value then 032 * returns the result. Please note that caller is responsible for 033 * synchronizing access to the list. 034 * 035 * @param data 036 * List to traverse and find max 037 * @return max number in the list or null if the list is empty. 038 */ 039 public Double evaluate(List<Double> data) { 040 if (data == null || data.size() == 0) { 041 return null; 042 } 043 Double max = null; 044 for (Double d : data) { 045 if (max == null) { 046 max = d; 047 } else { 048 if (max.doubleValue() < d.doubleValue()) { 049 max = d; 050 } 051 } 052 } 053 return max; 054 } 055 056 @Override 057 public String toString() { 058 return DoubleMaxAggregatorFunction.class.getName(); 059 } 060 061}