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

ı am trying to merge more than one hashmaps also sum the values of same key, ı 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. ı 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 ı 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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