代码错误import java.util.Scanner; public class Main{ public static void main (String args[]){ Scanner sc=new Scanner(System.in); double a=sc.nextDouble(); double b=sc.nextDouble(); Shape s=new Oval(a,b); System.out.println("The area of "+s.toString()+" is "+s.area()); System.out.println("The perimeterof "+s.toString()+" is "+s.perimeter()); }} class Shape{ abstract double area(); abstract double perimeter(); } class Oval extends Shape{ private double a; //长轴半径 private double b; //短轴半径 Oval(double a,double b){ this.a= a; this.b= b; } Oval(){ this.a=0; this.b=0; } double area(){ return Math.PI*a*b; } double perimeter(){ return 2*Math.PI*b+4*(a-b); //L=2πb+4(a-b) } public String toString() { return "Oval(a:" + this.a + ",b:" + this.b + ")"; } }

这段代码有一个错误，因为抽象类 Shape 中的方法没有被声明为抽象方法。在 Java 中，如果一个类有抽象方法，那么这个类必须被声明为抽象类。因此，你需要在 Shape 类中将 area() 和 perimeter() 方法声明为抽象方法，如下所示：

abstract class Shape {
    abstract double area();
    abstract double perimeter();
}

另外，你还需要将 Oval 类的构造函数声明为 public，否则在其他类中无法访问该构造函数。

修复后的代码如下：

import java.util.Scanner;

public class Main {
    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        double a = sc.nextDouble();
        double b = sc.nextDouble();
        Shape s = new Oval(a, b);
        System.out.println("The area of " + s.toString() + " is " + s.area());
        System.out.println("The perimeter of " + s.toString() + " is " + s.perimeter());
    }
}

abstract class Shape {
    abstract double area();

    abstract double perimeter();
}

class Oval extends Shape {
    private double a;    //长轴半径
    private double b;    //短轴半径

    public Oval(double a, double b) {
        this.a = a;
        this.b = b;
    }

    public Oval() {
        this.a = 0;
        this.b = 0;
    }

    @Override
    double area() {
        return Math.PI * a * b;
    }

    @Override
    double perimeter() {
        return 2 * Math.PI * b + 4 * (a - b); //L=2πb+4(a-b)
    }

    public String toString() {
        return "Oval(a:" + this.a + ",b:" + this.b + ")";
    }
}