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Java Demonstration on how to perform map reduce from a file to create an aggregation/report
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| import java.io.IOException; | |
| import java.nio.file.Files; | |
| import java.nio.file.Paths; | |
| import java.util.Objects; | |
| import java.util.Scanner; | |
| import java.util.stream.Stream; | |
| public class GameDataService{ | |
| private final GameDataRepository gameDataRepository; | |
| GameDataService(GameDataRepository gameDataRepository){ | |
| this.gameDataRepository = gameDataRepository; | |
| } | |
| public static void main(String[] args){ | |
| GameDataRepository gameDataRepository = new FileBasedGameDataRepository(args[0]); | |
| GameDataService gameDataService = new GameDataService(gameDataRepository); | |
| System.out.print("Specify Team name: "); | |
| Scanner scanner = new Scanner(System.in); | |
| String teamOfInterest = scanner.nextLine(); | |
| TeamStatistics teamStatistics = gameDataService.getTeamStatistics(teamOfInterest); | |
| String display = String.format( | |
| "Team %s - games: %d, wins: %d, losses: %d", | |
| teamStatistics.teamName, | |
| teamStatistics.numberOfGames, | |
| teamStatistics.numberOfWins, | |
| teamStatistics.numberOfLosses | |
| ); | |
| System.out.println(display); | |
| } | |
| private TeamStatistics getTeamStatistics(String teamName){ | |
| return gameDataRepository.getGameDataRelevantToTeam( | |
| Objects.requireNonNull(teamName, "Team name must not be null")) | |
| .reduce( | |
| TeamStatistics.createStatistics(teamName), | |
| TeamStatistics::processGameData, | |
| (previousStat, currentStat) -> currentStat | |
| ); | |
| } | |
| } | |
| interface GameDataRepository { | |
| Stream<GameData> getGameDataRelevantToTeam(String teamName); | |
| } | |
| class FileBasedGameDataRepository implements GameDataRepository{ | |
| private final String fileName; | |
| FileBasedGameDataRepository(String fileName){ | |
| this.fileName = fileName; | |
| } | |
| @Override | |
| public Stream<GameData> getGameDataRelevantToTeam(String teamName){ | |
| try{ | |
| return Files.lines(Paths.get(fileName)) | |
| .map(line -> line.split(",")) | |
| .filter(parts -> teamName.equals(parts[0]) || teamName.equals(parts[1])) | |
| .map(parts -> GameData.builder() | |
| .setHomeTeam(parts[0].trim()) | |
| .setAwayTeam(parts[1].trim()) | |
| .setHomeTeamScore(Integer.parseInt(parts[2].trim())) | |
| .setAwayTeamScore(Integer.parseInt(parts[3].trim())) | |
| .build() | |
| ); | |
| } catch (IOException e) { | |
| throw new RuntimeException(e); | |
| } | |
| } | |
| } | |
| class GameData { | |
| final String homeTeam; | |
| final String awayTeam; | |
| final int homeTeamScore; | |
| final int awayTeamScore; | |
| private GameData(String homeTeam, String awayTeam, int homeTeamScore, int awayTeamScore){ | |
| this.homeTeam = homeTeam; | |
| this.awayTeam = awayTeam; | |
| this.homeTeamScore = homeTeamScore; | |
| this.awayTeamScore = awayTeamScore; | |
| } | |
| static GameDataBuilder builder(){ | |
| return new GameDataBuilder(); | |
| } | |
| static class GameDataBuilder { | |
| private String homeTeam; | |
| private String awayTeam; | |
| private int homeTeamScore; | |
| private int awayTeamScore; | |
| private GameDataBuilder(){} | |
| GameDataBuilder setHomeTeam(String homeTeam){ | |
| this.homeTeam = homeTeam; | |
| return this; | |
| } | |
| GameDataBuilder setAwayTeam(String awayTeam){ | |
| this.awayTeam = awayTeam; | |
| return this; | |
| } | |
| GameDataBuilder setHomeTeamScore(int homeTeamScore){ | |
| this.homeTeamScore = homeTeamScore; | |
| return this; | |
| } | |
| GameDataBuilder setAwayTeamScore(int awayTeamScore){ | |
| this.awayTeamScore = awayTeamScore; | |
| return this; | |
| } | |
| GameData build(){ | |
| return new GameData(homeTeam, awayTeam, homeTeamScore, awayTeamScore); | |
| } | |
| } | |
| } | |
| class TeamStatistics { | |
| private static final int STARTING_COUNT = 0; | |
| final String teamName; | |
| final int numberOfGames; | |
| final int numberOfWins; | |
| final int numberOfLosses; | |
| static TeamStatistics createStatistics(String teamName){ | |
| return new TeamStatistics(Objects.requireNonNull(teamName), STARTING_COUNT, STARTING_COUNT, STARTING_COUNT); | |
| } | |
| private TeamStatistics(String teamName, int numberOfGames, int numberOfWins, int numberOfLosses){ | |
| this.teamName = teamName; | |
| this.numberOfGames = numberOfGames; | |
| this.numberOfWins = numberOfWins; | |
| this.numberOfLosses = numberOfLosses; | |
| } | |
| TeamStatistics processGameData(GameData gameData){ | |
| if(teamName.equals(gameData.homeTeam)) { | |
| return updateTeamStats(gameData.homeTeamScore, gameData.awayTeamScore); | |
| } else if(teamName.equals(gameData.awayTeam)) { | |
| return updateTeamStats(gameData.awayTeamScore, gameData.homeTeamScore); | |
| } | |
| return this; | |
| } | |
| private TeamStatistics updateTeamStats(int thisTeamScore, int otherTeamScore){ | |
| int updatedNumberOfGames = numberOfGames + 1; | |
| if(thisTeamScore < otherTeamScore){ | |
| return new TeamStatistics(teamName, updatedNumberOfGames, numberOfWins, numberOfLosses + 1); | |
| } else if(thisTeamScore > otherTeamScore) { | |
| return new TeamStatistics(teamName, updatedNumberOfGames, numberOfWins + 1, numberOfLosses); | |
| } else { | |
| return new TeamStatistics(teamName, updatedNumberOfGames, numberOfWins, numberOfLosses); | |
| } | |
| } | |
| } |
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