这两个函数如何用java8 新api改为one-liner

Question

方法都很简单, 不解释了. 如何用java8 的新api改为更优雅的 一行代码格式?

void addOne(Map<String, Integer> map, 
        String key, 
        int increment, 
        int defVal){
    if(map.containsKey(key))
        map.put(key, map.get(key) + increment);
    else
        map.put(key, defVal);
}

void addString(Map<String, Set<String>> map, 
               String key, 
               String val){
    if(!map.containsKey(key))
        map.put(key, new HashSet<>());
    map.get(key).add(val);
}

Answer 1

It should be possible to use several tool methods provided by the Map interface, as follows:

void addOne(Map<String, Integer> map, 
        String key, 
        int increment, 
        int defVal){
    // map.compute(key, (k, v) -> key.equals(k) ? v + increment : defVal);
    map.compute(key, (k, v) -> v == null ? defVal : v + increment)
}

void addString(Map<String, Set<String>> map, 
               String key, 
               String val){
    map.computeIfAbsent(key, k -> new HashSet<>()).add(val);
}