我有包含这样的数据的列表

game_id | user_id | status

1 1 STARTED

2 1 FINISHED

1 2 STARTED

2 2 FINISHED

我想将这个列表收集到两个地图中(如果可能的话,在一个地图中)

一张地图应该将user_id映射到用户玩的游戏数量 – 基本上是具有完成状态的游戏

user_id | finished_games

1 1

2 1

另一张地图应将user_id存储到所有游戏计数中.它看起来像这样

user_id | all_games

1 2

2 2

我是这样做的(我删除了game_id字段,因为它实际上并不重要)

import java.util.*;

import java.util.stream.*;

public class MyClass {

public static void main(String args[]) {

List games = Arrays.asList(

create("user-1", "STARTED"),

create("user-2", "STARTED"),

create("user-1", "FINISHED"),

create("user-2", "FINISHED"),

create("user-1", "FINISHED"),

create("user-2", "FINISHED")

);

// expect user-1: all_games (3), finished_games (2)

Map allGames = games

.stream()

.collect(Collectors.groupingBy(Game::getUserId, Collectors.counting()));

System.out.println(allGames);

Map finishedGames = games

.stream()

.filter(game -> game.battleStatus.equals("FINISHED"))

.collect(Collectors.groupingBy(Game::getUserId, Collectors.counting()));

System.out.println(finishedGames);

}

private static Game create(String id, String status) {

Game game = new Game();

game.userId = id;

game.battleStatus = status;

return game;

}

private static class Game {

String userId;

String battleStatus;

public String getUserId() {

return userId;

}

}

}

它似乎工作正常.但是当我计算具有状态的游戏时,我会过滤以便仅保留具有FINISHED状态的项目.

Map finishedGames = games

.stream()

.filter(game -> game.battleStatus.equals("FINISHED"))

.collect(Collectors.groupingBy(Game::getUserId, Collectors.counting()));

有没有办法实现内部收集块而不是使用过滤器?

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