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}