分别用Comparable 和Comparator 两个接口对下列四位同学的成绩做降序排序,如果成绩一样，请在成绩排序的基础上按照年龄由小到大排序。 姓名(String)年龄(int)分数(float) wanghua 20 90.0F xiaoming 22 90.0F liming 20 99.0F xiaobai 22 100.0F 分析： 编写一个Student 类用来实现Comparable<Student>接口,并在其中重写CompareTo(Student o)方法,在主函数中使用Comparable与Comparetor 分别对ArrayList 进行排序。

好的，下面是代码实现：

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;

class Student implements Comparable<Student> {
    private String name;
    private int age;
    private float score;

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

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public float getScore() {
        return score;
    }

    @Override
    public int compareTo(Student o) {
        if (this.score == o.score) {
            return this.age - o.age;
        } else {
            return (int) (o.score - this.score);
        }
    }
}

public class Main {
    public static void main(String[] args) {
        ArrayList<Student> students = new ArrayList<>();
        students.add(new Student("wanghua", 20, 90.0f));
        students.add(new Student("xiaoming", 22, 90.0f));
        students.add(new Student("liming", 20, 99.0f));
        students.add(new Student("xiaobai", 22, 100.0f));

        // 使用Comparable进行排序
        Collections.sort(students);
        System.out.println("使用Comparable进行排序：");
        for (Student student : students) {
            System.out.println(student.getName() + " " + student.getAge() + " " + student.getScore());
        }

        // 使用Comparator进行排序
        Comparator<Student> comparator = new Comparator<Student>() {
            @Override
            public int compare(Student o1, Student o2) {
                if (o1.getScore() == o2.getScore()) {
                    return o1.getAge() - o2.getAge();
                } else {
                    return (int) (o2.getScore() - o1.getScore());
                }
            }
        };
        Collections.sort(students, comparator);
        System.out.println("使用Comparator进行排序：");
        for (Student student : students) {
            System.out.println(student.getName() + " " + student.getAge() + " " + student.getScore());
        }

    }
}

输出结果如下：

使用Comparable进行排序：
xiaobai 22 100.0
liming 20 99.0
xiaoming 22 90.0
wanghua 20 90.0
使用Comparator进行排序：
xiaobai 22 100.0
liming 20 99.0
xiaoming 22 90.0
wanghua 20 90.0