@Test
    public void test4(){
        Map map=new LinkedHashMap();
        map.put("1", "aaa");
        map.put("2", "bbb");
        map.put("3", "ccc");
         
        //传统方式2
        Set set=map.keySet();
        Iterator it=set.iterator();
        while(it.hasNext()){
            Map.Entry entry = (Entry) it.next();
            String key=(String) entry.getKey();
            String valu=(String) entry.getValue();
            System.out.println(key + "=" + valu);
        }
        
    }