将对象列表转换为Map [英] Converting a list of objects to Map

问题描述

我正在尝试将玩家列表转换为地图.播放器包含名称&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));

我的问题是我正在尝试通过使用流合并运行来转换为地图，而无法通过.

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

分别尝试并合并值，如下所示，并获得预期结果.

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());
        });

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

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

推荐答案

您可以将toMap收集器用作:

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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