向map中追加元素

public class Demo01 {
    
    public static void main(String[] args) {
        
        String mapKey = "a";
        Map<String, Map<String, Integer>> maps = new ConcurrentHashMap<String,Map<String, Integer>>();
        Map<String, Integer> map = new HashMap<String,Integer>();
        map.put("aaaa", 1);
        map.put("bbbb", 2);
        map.put("cccc", 3);
        
        maps.put("a", map);
        
        if(maps.containsKey(mapKey)){
            Map<String, Integer> tmpMap = maps.get(mapKey);            
            tmpMap.put("dddd", 4);    
            maps.put(mapKey, tmpMap);
        }
        
        //遍历maps
        Iterator<String> it = maps.keySet().iterator();
        while(it.hasNext()){
            String mapsKey = it.next();        
            Map<String, Integer> mapValue = maps.get(mapsKey);
            System.out.println(mapValue);
        }
    }

}

输出结果：
{bbbb=2, dddd=4, aaaa=1, cccc=3}