集合(放物件)排序

用Collections.sort方法對list排序有兩種方法 
第一種是list中的物件實作Comparable介面，如下： 
[java] view plain copy 
/** 
* 依order對User排序 
*/  
public class User implements Comparable implements Comparable {  
     private String name;  
     private Integer order;  
        }  
     public void setName(String name) {  
         this.name = name;  ) {  
         return order;  
     }  
     public void set     }  
     public int compareTo(User arg0) {  
         return this.getOrder().compareTo(arg0.getOrder() );  
     }  
} 測試一下：  
public class Test{  
  
     public  );  
         user1.setName("a");  
         user1.setOrder (1);  
         User user2 = new User();  
         user2.setName(b");        List list = new ArrayList();  
         //此處add user2再add user1  
         list.add(user2);  
                 for(User u : list){  
             System.out.println(u.getName( ));  
         }  
     }  
}   

 
[java] view plain copy 
/** 
* 依order對User排序 
*/  
public class User { //此處無實作Comparable介面  
    private String name;  
     private Integer order;  return name;  
     }  
     public void setName(String name) {  
this.name = name;  
     }  
     public Integer getOrder() {  
       (Integer order) {  
         this.order = order;  
     }  
}  
  (HastSet——>List——>sort進行排序)：  
public class Test {  
    public static void main(String[] args) {  
    ("a");
        user1.setPrice(11);  
        User user2 = new User();       user2.setPrice(2);  

        Set Hset = new HashSet();  
        Hset.add(user2);        List list = new ArrayList();  
        list. addAll(Hset);  
  
  
        Collections.sort(list,new Comparator(){  
                  return arg0.getPrice().compareTo(arg1.getPrice()) ;  
            }  
        });  
     println(u.getName());  
        }  
    }  


輸出結果如下： 
a 


輸出結果如下： 
a 
b ，將。 return arg0.getOrder().compareTo(arg1.getOrder());    改為： 
return arg1.getOrder().compareTo(arg0.getOrder());   
就成降序的了。