22.Collections排序

package entity;
public class Student implements Comparable{
private int number=0;             //学号
    private String name="";         //学生姓名
    private String gender="";         //性别
    public int getNumber(){
        return number;
    }
    public void setNumber(int number){
        this.number=number;
    }
    public String getName(){
        return name;
    }
    public void setName(String name){
        this.name=name;
    }
    public String getGender(){
        return gender;
    }
    public void setGender(String gender){
        this.gender=gender;
    }
    public int compareTo(Object obj){
        Student student=(Student)obj;
        if(this.number==student.number){  
            return 0;            //如果学号相同，那么两者就是相等的
        }else if(this.number>student.getNumber()){ 
            return 1;            //如果这个学生的学号大于传入学生的学号
        }else{ 
            return -1;            //如果这个学生的学号小于传入学生的学号
        }
    }
}

package test;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import entity.Student;

public class CollectionsDemo {
    public static void main(String[] args) {
        Student student1=new Student();
        student1.setNumber(5);
        Student student2=new Student();
        student2.setNumber(2);
        Student student3=new Student();
        student3.setNumber(1);
        Student student4=new Student();
        student4.setNumber(4);
        ArrayList<Student> list=new ArrayList<Student>();
        list.add(student1);
        list.add(student2);
        list.add(student3);
        list.add(student4);
        System.out.println("-------排序前-------");
        Iterator<Student> iterator=list.iterator();
        while(iterator.hasNext()){
            Student stu=iterator.next();
            System.out.println(stu.getNumber());
        }
        //使用Collections的sort方法对list进行排序
        System.out.println("-------排序后-------");
        Collections.sort(list); 
        iterator=list.iterator();
        while(iterator.hasNext()){
            Student stu=iterator.next();
            System.out.println(stu.getNumber());
        } 
    }

}