如何遍历Map

太过爱你忘了你带给我的痛 2022-09-19 01:57 162阅读 0赞

//利用 Collection

Collection<Student> c = map.values();

Iterator it = c.iterator();  
for (; it.hasNext();) \{  
System.out.println(it.next());

原文：[http://www.cnblogs.com/kristain/articles/2033566.html][http_www.cnblogs.com_kristain_articles_2033566.html]

public static void main(String[] args) {
    
    
      Map<String, String> map = new HashMap<String, String>();
      map.put("1", "value1");
      map.put("2", "value2");
      map.put("3", "value3");
      
      //第一种：普遍使用，二次取值
      System.out.println("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
      System.out.println("通过Map.entrySet使用iterator遍历key和value：");
      Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
      while (it.hasNext()) {
       Map.Entry<String, String> 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
      System.out.println("通过Map.entrySet遍历key和value");
      for (Map.Entry<String, String> entry : map.entrySet()) {
       System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
      }
    
      //第四种
      System.out.println("通过Map.values()遍历所有的value，但不能遍历key");
      for (String v : map.values()) {
       System.out.println("value= " + v);
      }
     }

[http_www.cnblogs.com_kristain_articles_2033566.html]: http://www.cnblogs.com/kristain/articles/2033566.html