Collections.sort()メソッドオブジェクトのソート

 
  
 
   
Collections.sort()     List      ，             ，       ：
  
1. public static Comparable super T>> void sort(List list)
  
  Collection     ，  T      Comparable  ，  ：
  
class Employee implements Comparable{    private Integer pay; 
    public Employee(int pay){        this.pay=pay;    } 
     public void show(){         System.out.println(pay);     } 
     @Override     public int compareTo(Employee o) {         return this.pay.compareTo(o.pay);     }} 
テスト:
public class Test{    public static void main(String[] args) {      List list=new ArrayList();      list.add(new Employee(22));      list.add(new Employee(1));      list.add(new Employee(233));      list.add(new Employee(12));      list.add(new Employee(165)); 
      Collection.sort(list);      for(Employee e:list){          e.show();      } 
} 
出力結果は以下の通りです.
    1    12    22    165    233 
2.public static  void sort( 
List 
 list, 
Comparator 
super T> c)  
class Employer{     private Integer age;     public Employer(int age) {         this.age=age;     }    public void show(){         System.out.println(age);    }    public Integer getAge(){         return this.age;    }} 
テストしてみる
public class Test{ 
    public static void main(String[] args) {      List list=new ArrayList();      list.add(new Employer(22));      list.add(new Employer(1));      list.add(new Employer(233));      list.add(new Employer(12));      list.add(new Employer(165));      Collections.sort(list,new Comparator() {          @Override          public int compare(Employer o1, Employer o2) {              return o1.getAge().compareTo(o2.getAge());          }      });      for(Employer e:list){          e.show();      } 
    ｝ 
} 
    1    12    22    165    233 
まとめ:1つ目の方法は固定属性でしかソートできません.後者は柔軟ですが、コードはやや複雑です.