（一）循环例子

Map map = new HashMap();
        map.put("pen","thank you for attention");
        map.put("lao","thank you for attention");
        map.put("xi","thank you for attention");

（二）通过key Set key = map.keySet()

  for(String key:map.keySet()){
            System.out.println("key="+key+" value="+map.get(key));
        }

（三）key和value都循环

  for(Map.Entry entry : map.entrySet()){
            System.out.println("key="+entry.getKey()+" value="+entry.getValue());
        }

（四）迭代器

 Iterator> iterator = map.entrySet().iterator();
        while (iterator.hasNext()){
            Map.Entry entry = iterator.next();
            System.out.println("key="+entry.getKey()+" value="+entry.getValue());
        }

（五）仅循环value

 for(String value : map.values()){
            System.out.println("value="+value);
 }