使用Comparable接口的小例子

代码：

public class Student implements Comparable<Student> {

    private int id;

    private String name;

    private int age;

    public Student(int id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    @Override
    public int compareTo(Student o) {
        if (id > o.id) {
            return 1;
        } else if (id < o.id) {
            return -1;
        }
        return 0;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("学生的编号：" + id + ", ");
        sb.append("学生的姓名：" + name + ", ");
        sb.append("学生的年龄：" + age);
        return sb.toString();
    }
}

测试：

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class Test {
    public static void main(String[] args) {
        List<Student> list = new ArrayList<Student>();
        list.add(new Student(3, "ZhangSan", 21));
        list.add(new Student(2, "LiSi", 22));
        list.add(new Student(1, "WangWu", 23));

        System.out.println("排序前：");
        for (Student stu : list) {
            System.out.println(stu);
        }

        System.out.println("排序后：");
        Collections.sort(list); // 执行自动排序
        for (Student stu : list) {
            System.out.println(stu);
        }
    }
}