如何合并多个hashmaps也总结了java中同一个键的值 [英] how to merge more than one hashmaps also sum the values of same key in java

问题描述

<$ p我想要合并多个hashmaps也可以合计同一个键的值，
我想用下面的玩具示例来解释我的问题$ p> 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）;


ı尝试了putall

m.putAll （m2）;

输出如下
{banana = 6，apple = 9，pear = 3}

但其结果不适用于此问题。
我想输出为

香蕉= 6苹果= 11梨= 3

如果你使用的是Java 8，你可以使用新的 如何在java中获得这个结果？ href =http://docs.oracle.com/javase/8/docs/api/java/util/Map.html#merge-KV-java.util.function.BiFunction-> merge 方法（k，v） - > m.merge（k，v，（v1，v2） ）→> v1 + v2））;

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);

ı tried putall

m.putAll(m2);

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

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

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

how can ı get this result in java?

解决方案

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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