项目过程中遇到 类的排序 可以用这个类实现Comparable接口 ,重写comparaeTo方法来对这个类进行排序

在这个方法中 如果返回-1,则当前对象排在前面,如果返回1 ,则当前对象排在后面 ,返回0 .则相等

多的不说 直接上代码

实体类 :Student import java.text.SimpleDateFormat; import java.util.Date; /**  * @authot Administrator  * @create 2018-05-20 13:43  */ public class Student  implements Comparable
    
     {
      private Integer number;     private Double money;     private Date createdate;     public  Student (Integer number,Double money,Date createdate) {
          this.number = number;         this.money = money;         this.createdate = createdate;     }     public Integer getNumber() {
          return number;     }     public Student setNumber(Integer number) {
          this.number = number;         return this;     }     public Double getMoney() {
          return money;     }     public Student setMoney(Double money) {
          this.money = money;         return this;     }     public Date getCreatedate() {
          return createdate;     }     public Student setCreatedate(Date createdate) {
          this.createdate = createdate;         return this;     }     @Override     public String toString() {
          return  "number:"+number+";money:"+money+";createdate:"+new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(createdate);     }     @Override     public int compareTo(Student o) {
          if (this.number > o.number) {
              return -1;         }else if (this.number < o.number) {
              return 1;         }else{
              if (this.money > o.money) {
                  return 1;             }else if (this.money < o.money) {
                  return -1;             }else {
                return  this.createdate.compareTo(o.createdate);             }         }     } }
    

 里面三个字段 ,数量,总额,和创建时间 先比较数量 再比较总额 ,最后比较时间,一般到时间维度也就比较出来了

在比较时间的维度 的时候直接使用compareTo方法 因为在日期类中已经对compareTo方法做了重写 所以可以直接比较

测试类:

import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.Collections; import java.util.Date; import java.util.List; public class Main {
      public static void main(String[] args) throws Exception{
          List
    
      students = new ArrayList
     
      ();         SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");         students.add(new Student(1,400.0,format.parse("2018-05-20 13:01:02")));         students.add(new Student(2,300.0,format.parse("2018-05-20 13:20:02")));         students.add(new Student(3,200.0,format.parse("2018-05-20 13:14:02")));         students.add(new Student(4,100.0,format.parse("2018-05-20 13:16:02")));         students.add(new Student(5,500.0,format.parse("2018-05-20 13:08:02")));         students.add(new Student(5,500.0,format.parse("2018-05-20 13:08:03")));         students.add(new Student(3,500.0,format.parse("2018-05-20 13:08:02")));         students.add(new Student(1,600.0,format.parse("2018-05-20 13:08:02")));         Collections.sort(students);         for (Student student : students) {
              System.out.println(student);         }     } }
     
    

运行结果如下:

number:5;money:500.0;createdate:2018-05-20 13:08:02

number:5;money:500.0;createdate:2018-05-20 13:08:03

number:4;money:100.0;createdate:2018-05-20 13:16:02

number:3;money:200.0;createdate:2018-05-20 13:14:02

number:3;money:500.0;createdate:2018-05-20 13:08:02

number:2;money:300.0;createdate:2018-05-20 13:20:02

number:1;money:400.0;createdate:2018-05-20 13:01:02

number:1;money:600.0;createdate:2018-05-20 13:08:02

 

第一次写博客希望可以对你得到帮助,多多指教