使用while循环的Java菜单循环

时间:2018-01-29 22:01:51

标签: java loops while-loop menu joptionpane

我试图写一个循环,我让用户输入一个米的值,然后根据菜单给出他们会选择一个打印转换的选项,它应该运行直到用户输入4退出程序。但是我的程序无法无序地运行每个循环或不止一次,我不确定为什么。我知道转换和休息,但是我的老师不鼓励我们做任何我们尚未做的任何课程。

import javax.swing.JOptionPane;
public class Conversion_LAbA {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    //Junior Nieves Alvarez, Conversion LabA

    String inputString, inputOption;
    double meters, kilometers, inches, feet;
    int option;
    inputString = JOptionPane.showInputDialog("Enter the Meters value");
    meters = Double.parseDouble(inputString);
    if (meters < 1)
    {
        inputString =JOptionPane.showInputDialog("Enter the Meters value");
    }
    System.out.println("Choose one of the Following"
            + " 1. Convert to Kilometers"

            + " 2. Convert to Inches"

            + " 3. Convert to Feet"

            + " 4. Exit");
    inputOption = JOptionPane.showInputDialog("Choose an Option");
    option = Integer.parseInt(inputOption);
    while (option == 1)
    {
        kilometers = meters*0.001;
        System.out.println(kilometers);
        inputOption = JOptionPane.showInputDialog("Choose an Option");
        option = Integer.parseInt(inputOption);
    }
    while (option == 2)
    {
        inches = meters*39.37;
        System.out.println(inches);
        inputOption = JOptionPane.showInputDialog("Choose an Option");
        option = Integer.parseInt(inputOption);
    }
    while (option == 3)
    {
        feet= meters*3.281;
        System.out.println(feet);
        inputOption = JOptionPane.showInputDialog("Choose an Option");
        option = Integer.parseInt(inputOption);
    }
    if (option == 4)
    {
        System.out.println("The program will end");
        System.exit(0);
    }
}

}

3 个答案:

答案 0 :(得分:1)

您的逻辑存在一些问题。

  1. 您希望在while循环中包含米的输入,这样您就可以确保用户输入的仪表对程序执行的其余部分有效。

  2. 剩下要做的就是在while循环中使用if语句而不是while循环包装你的选项。这样您就可以选择一个选项,然后提示您在程序运行中尝试不同的转换,并能够以您想要的任何顺序输入您的选项。

  3. 最后,将测量符号放在输出旁边是有帮助的,这样当用户选择一个选项时,他们可以看到他们正在使用的转换,km为千米,“英寸和英尺”。

    String inputString, inputOption;
    double meters = 0, kilometers, inches, feet;
    int option = 0;
    
    while(meters < 1)
    {
        inputString = JOptionPane.showInputDialog("Enter the Meters value");
        meters = Double.parseDouble(inputString);
        if (meters < 1)
        {
        System.out.println("Invalid Meter value, please enter a value >= 1");
        option = 0;
        }
    }
    
    while(option != 4){
        System.out.println("Choose one of the Following"
                + "\n 1. Convert to Kilometers"
                + "\n 2. Convert to Inches"
                + "\n 3. Convert to Feet"
                + "\n 4. Exit");
        inputOption = JOptionPane.showInputDialog("Choose an Option");
        option = Integer.parseInt(inputOption);
        if(option == 1)
        {
            kilometers = meters*0.001;
            System.out.println(kilometers + "km");
        }
        else if(option == 2)
        {
            inches = meters*39.37;
            System.out.println(inches + "\"");
        }
        else if(option == 3)
        {
            feet= meters*3.281;
            System.out.println(feet + "'");
        }
        else if (option == 4)
        {
            System.out.println("The program will end");
        }
    }
    

答案 1 :(得分:0)

如果在每个选项上都有while循环,编译器将继续运行该循环,直到数字发生变化。这个数字不会改变,所以国家将保持不变。

您需要一个switch语句或一系列IF-ELSE语句。之前我有一位老师让我们做了IF-ELSE语句,向我们展示了很多选项带来的麻烦。然后他们给了我们转换声明。

答案 2 :(得分:0)

没有休息,没有开关,有一些验证

package com.qvs;

import javax.swing.JOptionPane;


public class Conversion_LAbA {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        //Junior Nieves Alvarez, Conversion LabA

        String inputString = "", inputOption;
        double meters;
        int option;
        for (;;) {
            inputString = JOptionPane.showInputDialog("Enter the Meters value");
            meters = Double.parseDouble(inputString);
            if (meters >= 1) {
                System.out.println("Choose one of the Following"
                        + " 1. Convert to Kilometers"

                        + " 2. Convert to Inches"

                        + " 3. Convert to Feet"

                        + " 4. Exit");


                option = 0;
                while ((option < 1) || (option > 4)) {
                    inputOption = JOptionPane.showInputDialog("Choose an Option");
                    option = Integer.parseInt(inputOption);
                    if (option == 1) {
                        System.out.println(meters * 0.001);
                    } else if (option == 2) {
                        System.out.println(meters * 39.37);
                    } else if (option == 3) {
                        System.out.println(meters * 3.281);
                    } else if (option == 4) {
                        System.out.println("The program will end");
                        System.exit(0);
                    } else {
                        System.out.println("Invalid option");
                    }
                }
            } else {
                System.out.println("Meters entered must be >= 1");
            }
        }
    }
}