有没有会的小伙伴解答一下吧

第二题的参考

public interface Shape {
    double area(double len);
}

public class Square implements Shape{
    @Override
    public double area(double len) {
        return len * len;
    }
}

public class Circle implements Shape{
    public static final Double PI = 3.14;
    @Override
    public double area(double r) {
        return PI * r * r;
    }
}

public class TestMain {
    public static void main(String[] args) {
        double len = 2;
        double r = 3;
        System.out.println("正方形的面积为："+new Square().area(len));
        System.out.println("圆形的面积为："+new Circle().area(r));
    }
}

对你有帮助的话，请采纳一下哈！

给你个第一题的参考：

//学生类
public class Student {
    private String name;
    private int age;
    public Student(String name, int age){
        this.name = name;
        this.age = age;
    }

    public void show(){
        System.out.println("学生信息：名字为" + this.name + ", 年龄为" + this.age);
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

//本科类
public class Undergraduate extends Student{
    private String degree;

    public Undergraduate(String name, int age) {
        super(name, age);
    }

    public Undergraduate(String name, int age, String degree){
        this(name, age);
        this.degree = degree;
    }
    public void show(){
        System.out.println("本科生信息：姓名为"+ super.getName() + ",年龄为"+ super.getAge() + ", 学位为" + this.degree);
    }

    public String getDegree() {
        return degree;
    }

    public void setDegree(String degree) {
        this.degree = degree;
    }
}

//测试
public class TestMain {
    public static void main(String[] args) {
        Student s1 = new Student("张三", 15);
        Undergraduate s2 = new Undergraduate("李四", 21, "学士");
        s1.show();
        s2.show();
    }
}

对你有帮助的话，请采纳一下哈！！！