jdk8Map操作，compute，computeIfPresent，merge方法

比如，统计出现的次数

List<String> animals = Arrays.asList("dog", "cat", "cat", "dog", "fish", "dog");

　　方法一：

Map<String, Integer> map = new HashMap<>();
        for (String animal : animals) {
            map.compute(animal, (k, v) -> v == null ? 1 : ++v);
        }

　　方法二：

Map<String, Integer> map1 = new HashMap<>();
        for (String animal : animals) {
            map1.putIfAbsent(animal, 0);
            map1.computeIfPresent(animal, (k, v) -> ++v);
        }

　　方法三：

Map<String, Integer> map2 = new HashMap<>();
        for (String animal : animals) {
            map2.putIfAbsent(animal, 0);
            map2.merge(animal, map2.get(animal), (k, v) -> ++v);
        }

　　输出结果如下

标签：Map,animals,HashMap,map2,merge,animal,compute,jdk8Map,String
来源： https://www.cnblogs.com/LiuFqiang/p/15272798.html