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January 13, 2018 17:36
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Java 8 version of tourist example (http://blog.dhananjaynene.com/2018/01/analysing-tourism-data-with-kotlin)
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| package com.rohankar.tourist; | |
| import io.vavr.Tuple3; | |
| import io.vavr.collection.Stream; | |
| import java.io.File; | |
| import java.io.IOException; | |
| import java.nio.file.Files; | |
| import java.util.Arrays; | |
| import java.util.List; | |
| import static java.util.Comparator.naturalOrder; | |
| import static java.util.stream.Collectors.toList; | |
| /** | |
| * Java 8 (using Vavr) version of original Tourist example written in Kotlin. | |
| * See: http://blog.dhananjaynene.com/2018/01/analysing-tourism-data-with-kotlin | |
| * | |
| * @author Sagar Rohankar | |
| */ | |
| public class Tourist { | |
| public static void main(String[] args) throws IOException { | |
| Stream<String> strings = Stream.ofAll(Files.readAllLines(new File("tourists-to-india.csv").toPath())); | |
| strings | |
| .drop(1) // csv header | |
| .dropRight(1) // total row | |
| .map(row -> row.split(",")) | |
| .map(arr -> { | |
| List<Integer> visitors = Arrays.stream(Arrays.copyOfRange(arr, 2, arr.length)) | |
| .mapToInt(Integer::parseInt) | |
| .boxed() | |
| .collect(toList()); | |
| return new Tuple3<>(arr[0], arr[1], visitors); // <Country, Continent, Visitors> | |
| }) | |
| .groupBy(countryContinentVisitors -> countryContinentVisitors._2) // by Continent | |
| .mapValues(tuple -> { | |
| int tourist2001 = tuple.map(Tuple3::_3) | |
| .map(l -> l.get(0)) | |
| .sum() | |
| .intValue(); | |
| int tourist2015 = tuple.map(Tuple3::_3) | |
| .map(l -> l.get(14)) | |
| .sum() | |
| .intValue(); | |
| double pctGrowth = (tourist2015 - tourist2001) * 100 / tourist2001; | |
| String maxCountry = tuple | |
| .sortBy(t -> t._3() | |
| .stream() | |
| .mapToInt(Integer::intValue) | |
| .sum()) | |
| .last() | |
| ._1; | |
| return new Tuple3<>(tourist2015, pctGrowth, maxCountry); | |
| }) | |
| .map(tuple -> tuple._2) // skip tuple._1 which is continent | |
| .sorted(naturalOrder()) | |
| .forEach(System.out::println); | |
| } | |
| } |
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