面试题-给定一个“flatten”Dictionary对象，根据键转换成嵌套字典对象

题目：

给定一个“Flatten” Dictionary 对象其键是点分割的，例如:{"A":1,"B.A":2,"B.B":3,"CC.D.E":4,"CC.D.F":5},实现一个函数，将其转换 为一个嵌套的字典对象，根据上面例子，嵌套对象结果为{A:1,"B":{"A":2,"B":3},"CC":{"D":{"E":4,"F":5}}}

答案

    /*** {A：1, B.A:2 B.B:3 CC.D.E:4 CC.DF:5}* @param args*/public static void main(String[] args) {
    Map<String, Integer> flatten = new HashMap<>();//生成例子数据flatten.put("A",1);flatten.put("B.A",2);flatten.put("B.B",3);flatten.put("CC.D.E",4);flatten.put("CC.D.F",5);Map<String, Object> newFlatten = new HashMap<>();flatten.forEach((key,val)->{
    recursion(key,newFlatten, val);});System.out.println(flatten);System.out.println(newFlatten);}/*** 递归方法* @param key* @param map* @param val*/public  static void recursion(String key ,Map<String,Object> map,Integer val){
    boolean contains = key.contains(".");//最后一个赋值if(!contains){
    map.put(key,val);}else{
    String beforeKey = StrUtil.subBefore(key, ".", false);String afterKey = StrUtil.subAfter(key, ".", false);HashMap<String, Object> newMap = new HashMap<>();if (!map.containsKey(beforeKey)){
    map.put(beforeKey,newMap);}else {
    newMap = (HashMap<String, Object>) map.get(beforeKey);}recursion(afterKey,newMap,val);}}