Map的遍历有四种方法,以下面这个Map为例:
Map<String, Object> map = new HashMap<String, Object>(); map.put("1", new Object()); map.put("2", new Object()); map.put("3", new Object());
//第一种:普遍使用,二次取值,通过Map.keySet遍历key和value for (String key : map.keySet()) { System.out.println("key= "+ key + " and value= " + map.get(key)); }
//第二种:通过Map.entrySet使用iterator遍历key和value Iterator<Map.Entry<String, Object>> it = map.entrySet().iterator(); while (it.hasNext()) { Map.Entry<String, Object> entry = it.next(); System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue()); }
//第三种:推荐,尤其是容量大时,通过Map.entrySet遍历key和value for (Map.Entry<String, Object> entry : map.entrySet()) { System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue()); }
//第四种:通过Map.values()遍历所有的value,但不能遍历key for (Object v : map.values()) { System.out.println("value= " + v); }