1 public class Demo01 {
2
3 public static void main(String[] args) {
4
5 String mapKey = "a";
6 Map<String, Map<String, Integer>> maps = new ConcurrentHashMap<String,Map<String, Integer>>();
7 Map<String, Integer> map = new HashMap<String,Integer>();
8 map.put("aaaa", 1);
9 map.put("bbbb", 2);
10 map.put("cccc", 3);
11
12 maps.put("a", map);
13
14 if(maps.containsKey(mapKey)){
15 Map<String, Integer> tmpMap = maps.get(mapKey);
16 tmpMap.put("dddd", 4);
17 maps.put(mapKey, tmpMap);
18 }
19
20 //遍历maps
21 Iterator<String> it = maps.keySet().iterator();
22 while(it.hasNext()){
23 String mapsKey = it.next();
24 Map<String, Integer> mapValue = maps.get(mapsKey);
25 System.out.println(mapValue);
26 }
27 }
28
29 }
30
31 输出结果：
32 {bbbb=2, dddd=4, aaaa=1, cccc=3}
