如何合并多个hashmaps还对java中相同键的值求和

问题描述

我正在尝试合并多个哈希图也对相同键的值求和，我想用玩具示例解释我的问题如下

am trying to merge more than one hashmaps also sum the values of same key, want to explain my problem with toy example as follows

    HashMap<String, Integer> m = new HashMap<>();
    HashMap<String, Integer> m2 = new HashMap<>();

    m.put("apple", 2);
    m.put("pear", 3);
    m2.put("apple", 9);
    m2.put("banana", 6);

我试过putall

m.putAll(m2);

m.putAll(m2);

输出如下{香蕉=6，苹果=9，梨=3}

output is as follows {banana=6, apple=9, pear=3}

但它的结果不适用于这个问题.我想输出为

but its result is not true for this problem. want to output as

{香蕉=6，苹果=11，梨=3}

{banana=6, apple=11, pear=3}

我如何在 java 中得到这个结果?

how can get this result in java?

推荐答案

如果你使用的是Java 8，你可以使用新的merge Map的方法.

If you are using Java 8, you can use the new merge method of Map.

m2.forEach((k, v) -> m.merge(k, v, (v1, v2) -> v1 + v2));

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