周长计算器 Java

Question

我正在尝试编写一个能够计算圆形、三角形或矩形周长的程序。但是程序运行不正确，它只显示菜单但我无法输入任何内容。

public class GeometryDriver 
{

public static void main(String[] args) 
{


  double radius;
  double side1 = 0; 
  double side2 = 0;
  double side3 = 0; 
  double length =0;
  double width =0; 
  double perimeter = 0;
  String userChoice;

    Scanner keyboard = new Scanner(System.in);
    int option;


    System.out.println("Welcome to the Geometry Calculator!\n"
            + "In this program we will use a menu to decide what kind of shape we will create.\n"
            + "\n1.Create and Calculate Perimeter of a Circle"
            + "\n2. Create and Calculate Perimeter of a Rectangle"
            + "\n3. Create and Calculate Perimeter of a Triangle");



    String input;
    GeometricShape aShape = null;

    option = keyboard.nextInt();




    switch (option)
    {
        case 1:



            input = JOptionPane. showInputDialog(null, "Enter the radius: ");
            radius = Double.parseDouble(input);
            aShape = new GeometricShape(radius);
            perimeter = aShape.getPerimeter();


            aShape = new GeometricShape(radius);
            break;

        case 2:


            input = JOptionPane.showInputDialog(null, "Enter the length: ");

            length = Double.parseDouble(input);

            perimeter = aShape.getPerimeter();
            input = JOptionPane.showInputDialog(null, "Enter the width: ");
            width = Double.parseDouble(input);

            aShape = new GeometricShape (length, width);


            break;
        case 3:

            perimeter = aShape.getPerimeter();

            input = JOptionPane.showInputDialog(null, "Enter side 1: ");
            input = JOptionPane.showInputDialog(null, "Enter side 2: ");
            input = JOptionPane.showInputDialog(null, "Enter side 3: ");
            side1 = Double.parseDouble(input);
            side2 = Double.parseDouble(input);
            side3 = Double.parseDouble(input);

            aShape = new GeometricShape (side1, side2, side3);

            break;
        default:

                    }


      System.out.println(aShape + " has perimeter" + perimeter);
}

}

还有……

public class GeometricShape 
{
    private double side1, side2, side3;
    private double radius; 
    private double length, width; 
    private boolean triangle = false;
    private boolean rectangle = false;
    private boolean circle = false;`


    public GeometricShape(double aSide1, double aSide2, double aSide3)
    {
        side1 = aSide1;
        side2 = aSide2;
        side3 = aSide3;
        triangle = true;
    }

    public GeometricShape(double aLength, double aWidth)
    {
        length = aLength;
        width = aWidth;
        rectangle = true;
    }


    public GeometricShape(double aRadius)
    {
        radius = aRadius;
        circle = true;
    }

    public double getRadius()
    {
        return radius;
    }

    public double getSide1()
    {
        return side1;
    }

    public double getSide2()
    {
        return side2;
    }

    public double getSide3()
    {
        return side3;
    }

    public double getLength()
    {
        return length;
    }

    public double getWidth()
    {
    return width;
    }

    public void setRadius(double aRadius)
    {
        radius = aRadius;
    }

    public void setSide1(double aSide1)
    {
        side1 = aSide1;
    }

    public void setSide2(double aSide2)
    {
        side2 = aSide2;
    }

    public void setSide3(double aSide3)
    {
        side3 = aSide3;
    }

    public void setLength(double aLength)
    {
        length = aLength;
    }

    public void setWidth(double aWidth)
    {
        width = aWidth;
    }

    public double getPerimeter()
    {

        double perimeter = 0;


        if (triangle == true)
        {
            perimeter = side1 + side2 + side3; 
        }

        else if (rectangle == true)
        {
            perimeter = (2* length) + (2*width);
        }

        else if (circle == true)
        {
            perimeter = 2* Math.PI * radius; 
        }  

    }

    public String toString()
    {
        return "The perimeter is: " + this.getPerimeter(); 
    }
}

Answer 1

新答案 好激动的消息！它确实有效！

考虑一下：

        Scanner keyboard = new Scanner(System.in);
        JOptionPane.showInputDialog(null, "Dialog Box 1: ");
        System.out.println("Write something");
        keyboard.nextInt();

它工作正常吗？但是，当您键入此内容时

        Scanner keyboard = new Scanner(System.in);
        System.out.println("Write something");
        keyboard.nextInt();
        JOptionPane.showInputDialog(null, "Dialog Box 1: ");

它似乎停止工作。我挑战你最小化控制台的窗口。在它后面，你会发现你的对话框说“DialogBox 1:”。这显然不理想，因为您的应用程序的用户将无法使用它。

因此，您可以使用的一种解决方法是将键盘输入更改为对话框，如下所示：

String displayMessage = "Welcome to the Geometry Calculator!\n"
            + "In this program we will use a menu to decide what kind of shape we will create.\n"
            + "\n1.Create and Calculate Perimeter of a Circle"
            + "\n2. Create and Calculate Perimeter of a Rectangle"
            + "\n3. Create and Calculate Perimeter of a Triangle";



    String input;
    GeometricShape aShape = null;

    option = Integer.parseInt(JOptionPane.showInputDialog(displayMessage));

更多信息 这个问题已经讨论过几次了。 JOptionPane.showMessageDialog is not showing 和 JOptionPane and Scanner input issue。 第二个解释了一种使用方法：

SwingUtilities.invokeLater(new Runnable() {

解决问题。

但是，为了简单起见，我建议您坚持使用扫描仪或对话框

Answer 2

对您的代码稍作修改后，我可以输入一个半径。它现在都在一个名为Main.java 的文件中，并且仍然是矩形的空指针，因为宽度为空。

import javax.swing.*;
import java.util.Scanner;

class GeometricShape {
    private double side1, side2, side3;
    private double radius;
    private double length, width;
    private boolean triangle = false;
    private boolean rectangle = false;
    private boolean circle = false;

    GeometricShape(double aSide1, double aSide2, double aSide3) {
        side1 = aSide1;
        side2 = aSide2;
        side3 = aSide3;
        triangle = true;
    }

    GeometricShape(double aLength, double aWidth) {
        length = aLength;
        width = aWidth;
        rectangle = true;
    }


    GeometricShape(double aRadius) {
        radius = aRadius;
        circle = true;
    }

    public double getRadius() {
        return radius;
    }

    public double getSide1() {
        return side1;
    }

    public double getSide2() {
        return side2;
    }

    public double getSide3() {
        return side3;
    }

    public double getLength() {
        return length;
    }

    public double getWidth() {
        return width;
    }

    public void setRadius(double aRadius) {
        radius = aRadius;
    }

    public void setSide1(double aSide1) {
        side1 = aSide1;
    }

    public void setSide2(double aSide2) {
        side2 = aSide2;
    }

    public void setSide3(double aSide3) {
        side3 = aSide3;
    }

    public void setLength(double aLength) {
        length = aLength;
    }

    public void setWidth(double aWidth) {
        width = aWidth;
    }

    public double getPerimeter() {

        double perimeter = 0;


        if (triangle == true) {
            perimeter = side1 + side2 + side3;
        } else if (rectangle == true) {
            perimeter = (2 * length) + (2 * width);
        } else if (circle == true) {
            perimeter = 2 * Math.PI * radius;
        }
        return perimeter;

    }


    public String toString() {


        return "The perimeter is: " + this.getPerimeter()
                ;
    }

}


public class Main {

    public static void main(String[] args) {
        {


            double radius;
            double side1 = 0;
            double side2 = 0;
            double side3 = 0;
            double length = 0;
            double width = 0;
            double perimeter = 0;
            String userChoice;

            Scanner keyboard = new Scanner(System.in);
            int option;


            System.out.println("Welcome to the Geometry Calculator!\n"
                    + "In this program we will use a menu to decide what kind of shape we will create.\n"
                    + "\n1.Create and Calculate Perimeter of a Circle"
                    + "\n2. Create and Calculate Perimeter of a Rectangle"
                    + "\n3. Create and Calculate Perimeter of a Triangle");


            String input;
            GeometricShape aShape = null;

            option = keyboard.nextInt();


            switch (option) {
                case 1:


                    input = JOptionPane.showInputDialog(null, "Enter the radius: ");
                    radius = Double.parseDouble(input);
                    aShape = new GeometricShape(radius);
                    perimeter = aShape.getPerimeter();


                    aShape = new GeometricShape(radius);
                    break;

                case 2:


                    input = JOptionPane.showInputDialog(null, "Enter the length: ");

                    length = Double.parseDouble(input);

                    perimeter = aShape.getPerimeter();
                    input = JOptionPane.showInputDialog(null, "Enter the width: ");
                    width = Double.parseDouble(input);

                    aShape = new GeometricShape(length, width);


                    break;
                case 3:

                    perimeter = aShape.getPerimeter();

                    input = JOptionPane.showInputDialog(null, "Enter side 1: ");
                    input = JOptionPane.showInputDialog(null, "Enter side 2: ");
                    input = JOptionPane.showInputDialog(null, "Enter side 3: ");
                    side1 = Double.parseDouble(input);
                    side2 = Double.parseDouble(input);
                    side3 = Double.parseDouble(input);

                    aShape = new GeometricShape(side1, side2, side3);

                    break;
                default:

            }


            System.out.println(aShape + " has perimeter" + perimeter);
            ;

        }
    }
}

测试

Welcome to the Geometry Calculator!
In this program we will use a menu to decide what kind of shape we will create.

1.Create and Calculate Perimeter of a Circle
2. Create and Calculate Perimeter of a Rectangle
3. Create and Calculate Perimeter of a Triangle
1
The perimeter is: 12.566370614359172 has perimeter12.566370614359172