75 lines
3.0 KiB
Java
75 lines
3.0 KiB
Java
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/*
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* Copyright 2023 The original authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package dev.morling.onebrc;
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import java.io.IOException;
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import java.nio.file.Files;
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import java.nio.file.Paths;
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import java.util.Map;
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import java.util.TreeMap;
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import java.util.stream.Collectors;
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public class CalculateAverage_anandmattikopp {
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private static final String FILE = "./measurements.txt";
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public static void main(String[] args) throws IOException {
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Map<String, StationStatistics> stationStatisticsMap = Files.lines(Paths.get(FILE)).parallel()
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.map(entry -> {
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String[] tokens = entry.split(";");
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return new Station(tokens[0], Double.parseDouble(tokens[1]));
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})
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.collect(
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Collectors.toConcurrentMap(
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station -> station.stationName,
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station -> new StationStatistics(station),
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StationStatistics::merge));
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System.out.println(new TreeMap<>(stationStatisticsMap));
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}
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private record Station(String stationName, double temperature) {
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}
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private record StationStatistics(String stationName, double minTemp, double meanTemp, double maxTemp,
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long totalCount) {
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StationStatistics(Station station) {
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//Calling canonical constructor
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this(station.stationName, station.temperature, station.temperature, station.temperature, 1);
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}
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//Merging two stats to create new stats
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public static StationStatistics merge(StationStatistics stats1, StationStatistics stats2) {
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assert stats1.stationName.equals(stats2.stationName);
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return new StationStatistics(
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stats1.stationName,
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Math.min(stats1.minTemp, stats2.minTemp), // minimum of both the temp
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(stats1.meanTemp * stats1.totalCount + stats2.meanTemp * stats2.totalCount) / (stats1.totalCount + stats2.totalCount), // average of both the average temps from stats
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Math.max(stats1.maxTemp, stats2.maxTemp), // maximum of both the temp
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stats1.totalCount + stats2.totalCount // increment the totalCount
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);
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}
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@Override
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public String toString() {
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return round(minTemp) + "/" + round(meanTemp) + "/" + round(maxTemp);
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}
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private double round(double value) {
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return Math.round(value * 10.0) / 10.0;
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}
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}
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}
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