Java - 解决 DemoSquare 问题

Question

我遇到问题的第一段代码是 DemoSquare - 当我运行它时它会崩溃。错误是:

Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - cannot find symbol
  symbol:   variable area
  location: class Square
    at Square.computeSurfaceArea(DemoSquare.java:57)
    at DemoSquare.main(DemoSquare.java:23)
Java Result: 1

我的代码是 -

// package demosquare;
import java.util.*;

public class DemoSquare {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        System.out.println("Please enter the height of the square/rectangle");
        double sqHeight = input.nextDouble();
        System.out.println("Please enter the width of the square/rectangle");
        double sqWidth = input.nextDouble();

        System.out.println("Please enter the height of the Cube/Rectangular Prism");
        double cuHeight = input.nextDouble();
        System.out.println("Please enter the width of the Cube/Rectangular Prism");
        double cuWidth = input.nextDouble();
        System.out.println("Please enter the depth of the Cube/Rectangular Prism");
        double cuDepth = input.nextDouble();

        // Create a square and print out the information about it
        Square square = new Square(sqHeight, sqWidth);
        System.out.println("A Square with dimensions " + square.getHeight()
                + " by " + square.getWidth() + " has a surface area of "
                + square.computeSurfaceArea());
        // Create a cube and print out the information about it.
        Cube cube = new Cube(cuHeight, cuWidth, cuDepth);
        System.out.println("A Cube with dimensions " + cube.getHeight()
                + " by " + cube.getWidth() + " by " + cube.getDepth() + " has a surface area of "
                + cube.computeSurfaceArea());

    } //  end main method
}  //end class DemoSquare

class Square {
    // enter the code to create the square class here

    double sqHeight = 0;
    double sqWidth = 0;

    public Square(double height, double width) {
        sqHeight = height;
        sqWidth = width;
    }

    public double getWidth() {
        return sqWidth;
    }

    public double getHeight() {
        return sqHeight;
    }

    public double computeSurfaceArea() {
        double surfaceArea = sqHeight * sqWidth;
        surfaceArea = (getHeight() * getWidth());
        return area;
    }
}

class Cube extends Square {

    double sqDepth = 0.00;
    // enter the cube class code here

    public Cube(double height, double width, double depth) {
        super(height, width);
        sqDepth = depth;
    }

    @Override
    public double getWidth() {
        return sqWidth;
    }

    @Override
    public double getHeight() {
        return sqHeight;
    }

    public double getDepth() {
        return sqDepth;
    }

    @Override
    public double computeSurfaceArea() {
        //Surface Area = 2hw + 2wd + 2dh
        double tsa = (2 * sqHeight * sqWidth) + (2 * sqWidth * sqDepth) + (2 * sqDepth * sqHeight);

        return tsa;
    }
}

我在这段代码中做错了什么？

Answer 1

您可以通过堆栈跟踪来判断错误所在。让我们回顾一下。

1. 程序无法运行的原因:

   Exception in thread "main" java.lang.RuntimeException: Uncompilable source code

   这意味着您的代码当前已损坏，并且至少在编译之前不会以任何方式执行。

   Uncompilable source code - cannot find symbol

   symbol: variable area

   这意味着有一个名为 area 的未知变量已在您的代码中使用但从未声明。

2. 然后是错误的位置:

   location: class Square

   at Square.computeSurfaceArea(DemoSquare.java:57)

   现在我们可以去哪里寻找了。让我们转到 Square 类的 computeSurfaceArea 方法中，更具体地说，位于文件 DemoSquare.java 的第 57 行。

   //54. public double computeSurfaceArea() {
   //55.     double surfaceArea = sqHeight * sqWidth;
   //56.     surfaceArea = (getHeight() * getWidth());
   //57.     return area;
   //58. }
   

   现在我们找到了罪魁祸首:return area;。注意这里的area是一个未声明的变量。正如其他答案中所述，您可能打算使用 surfaceArea 代替。

   //54. public double computeSurfaceArea() {
   //55.     double surfaceArea = sqHeight * sqWidth;
   //56.     surfaceArea = (getHeight() * getWidth());
   //57.     return surfaceArea;
   //58. }
   

进行此更改，代码将被修复到现在。

执行相同的过程来修复代码中的其他问题。

当您在运行时遇到其他异常(例如 NullPointerException)时，请执行类似的过程。