大一JAVA招新题希望各位大能能解答

Question

设计一个形状Shape抽象类和它的两个实现类：圆Circle和矩形Rectangle，实现各自构造方法、 area()方法计算图形的面积。让Rectangle类实现Comparable接口，能根据面积进行排序。
并编写相应测试类
Circle类：定义一个double类型的字段r，代表圆的半径；
Rectangle类：定义两个double类型的字段width和height，分别代表矩形的宽和高；
注意：Rectangle类，使其实现java.lang.Comparable接口，compareTo方法根据面积进行比较大小

Answer 1

我写

//shape类
public abstract class Shape {
    abstract Double area();
}

//Circle类
public class Circle extends Shape{
    private Double r;
    public Circle(Double radus) {
        this.r=radus;
    }
    @Override
    Double area() {
        return 3.14*this.r*this.r;
    }

}


//Rectangle 类
public class Rectangle extends Shape implements Comparable<Rectangle>{
    private Double width;
    private Double height;
    public Rectangle(Double w,Double h) {
        this.height=h;
        this.width=w;
    }
    @Override
    public Double area() {
        return this.height*this.width;
    }
    @Override
    public int compareTo(Rectangle o) {
        if(this.area()>o.area())
            return 1;
        else
            return 0;
    }
}


public class TestClass {
    public static void main(String[] args) {
        Circle c=new Circle(3.0);
        System.out.println(c.area());
        Rectangle r1=new Rectangle(2.3,4.5);
        System.out.println(r1.area());
        Rectangle r2=new Rectangle(1.4, 6.8);
        System.out.println(r2.area());
        if(r1.compareTo(r2)==1) {
            System.out.println("矩形r1的面既大");
        }else {
            System.out.println("矩形r2的面既大");
        }
    }
}