public static void main(String[] args) {

         Map<Integer, String> map = new HashMap<Integer, String>();

         map.put(8, "liusan");

         map.put(2, "liliu");

         map.put(3, "wuusan");

         map.put(1, "zhangqi");

         // 取出map中的所有元素。通过Keyset获取map中所有键的set集合，再通过Set的迭代器获取每一个键，再获取每一个键的值

         Set keySet = map.keySet();

         for (Iterator iterator = keySet.iterator(); iterator.hasNext();) {

             Integer key = (Integer) iterator.next();

             String value = map.get(key);

             System.out.println(key + ":" + value);

         }

     }