java ArrayList 排序

Java如何对ArrayList中对象按照该对象某属性排序

增加排序功能，打印时：输出学生对象的时候，需要先按照年龄排序，如果年龄相同，则按照姓名排序，如果姓名也相同，则按照学号排序。

    import java.util.ArrayList;  
    import java.util.Collections;  
    import java.util.Comparator;  
      
    public class ComparableTest {  
     public static void main(String[] args) {  
      Comparator<Student> comparator = new Comparator<Student>(){  
       public int compare(Student s1, Student s2) {  
        //先排年龄  
        if(s1.age!=s2.age){  
         return s1.age-s2.age;  
        }  
        else{  
         //年龄相同则按姓名排序  
         if(!s1.name.equals(s2.name)){  
          return s1.name.compareTo(s2.name);  
         }  
         else{  
          //姓名也相同则按学号排序  
          return s1.id-s2.id;  
         }  
        }  
       }  
      };  
      Student stu1 = new Student (1,"zhangsan","male",28,"cs");  
      Student stu2 = new Student (2,"lisi","female",19,"cs");  
      Student stu3 = new Student (3,"wangwu","male",22,"cs");  
      Student stu4 = new Student (4,"zhaoliu","female",17,"cs");  
      Student stu5 = new Student (5,"jiaoming","male",22,"cs");  
      
      ArrayList<Student> List = new ArrayList<Student>();  
      List.add(stu1);  
      List.add(stu2);  
      List.add(stu3);  
      List.add(stu4);  
      List.add(stu5);   
      //这里就会自动根据规则进行排序  
      Collections.sort(List,comparator);  
      display(List);  
     }  
       
     static void display(ArrayList<Student> lst){  
      for(Student s:lst)  
       System.out.println(s);  
     }  
    }  
      
    class Student{  
     int age;  
     int id;  
     String gender;  
     String name;  
     String cs;  
     Student(int id,String name,String gender,int age,String cs){  
      this.age=age;  
      this.name=name;  
      this.gender=gender;  
      this.id=id;  
      this.cs=cs;  
     }  
     public String toString(){  
      return id+"  "+name+"  "+gender+"  "+age+"  "+cs;  
     }  
    }  

 

public class User { //此处无需实现Comparable接口
    private String name;
    private Integer order;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getOrder() {
        return order;
    }
    public void setOrder(Integer order) {
        this.order = order;
    }
}

public class Test{
    public static void main(String[] args) {
        User user1 = new User();
        user1.setName("a");
        user1.setOrder(1);
        User user2 = new User();
        user2.setName("b");
        user2.setOrder(2);
        List<User> list = new ArrayList<User>();
        list.add(user2);
        list.add(user1);
       
        Collections.sort(list,new Comparator<User>(){
            public int compare(User arg0, User arg1) {
                return arg0.getOrder().compareTo(arg1.getOrder());
            }
        });
        for(User u : list){
            System.out.println(u.getName());
        }
    }
}

　　

/**
* 根据order对User排序
*/
public class User implements Comparable<User>{
    private String name;
    private Integer order;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getOrder() {
        return order;
    }
    public void setOrder(Integer order) {
        this.order = order;
    }
    public int compareTo(User arg0) {
        return this.getOrder().compareTo(arg0.getOrder());
    }
}

public class Test{

    public static void main(String[] args) {
        User user1 = new User();
        user1.setName("a");
        user1.setOrder(1);
        User user2 = new User();
        user2.setName("b");
        user2.setOrder(2);
        List<User> list = new ArrayList<User>();
        //此处add user2再add user1
        list.add(user2);
        list.add(user1);
        Collections.sort(list);
        for(User u : list){
            System.out.println(u.getName());
        }
    }
}