将对象列表转换为 Map

2022-01-08 00:00:00 hashmap java java-stream

我正在尝试将玩家列表转换为地图.播放器包含名称和作为变量运行.

I'm trying to convert a list of players into map. player contains name & runs as variables.

List<Player> runnerList = Arrays.asList(new Player("Virat", 4654), new Player("Jaddu", 5798),
            new Player("Dhoni", 4581), new Player("Virat", 8709), new Player("Dhoni", 4711),
            new Player("Virat", 4541));

我的问题是我试图通过使用流组合运行而不是通过来转换为地图.

my problem is i'm trying to convert to map by combining the runs using streams and not getting through.

对每个都进行了尝试并合并了值，如下所示，并获得了预期的结果.

Tried for each and merged the values, like below, and getting expected result.

playerList.forEach(n -> {
            mapVal.merge((n.getName()), (n.getDistance()), (val1, val2) -> IntStream.of(val1, val2).sum());
        });

结果将是 {Dhoni=9292, Jaddu=5798, Virat=17904}，正在寻找使用流的解决方案.

result would be {Dhoni=9292, Jaddu=5798, Virat=17904}, looking for a solution using streams.

推荐答案

你可以使用toMap Collector作为:

You can use toMap Collector as:

Map<String, Integer> mapVal = playerList.stream()
        .collect(Collectors.toMap(Player::getName,
                Player::getDistance, Integer::sum));

或groupingBy为:

Map<String, Integer> mapVal = playerList.stream()
        .collect(Collectors.groupingBy(Player::getName,
                Collectors.summingInt(Player::getDistance)));

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