利用keyset遍历Map

//利用keyset进行遍历，它的优点在于可以根据你所想要的key值得到你想要的 values，更具灵活性

    public static void workByKeySet(Map<String, Student> map) {         Set<String> key = map.keySet();         for (Iterator it = key.iterator(); it.hasNext();) {             String s = (String) it.next();             System.out.println(map.get(s));         }     }