Question

我在java中编写一个简单的计算器，只需2个操作数即可执行4个基本操作。我需要的是，在if语句中，我想执行一个循环，用户在要求继续时将继续执行相同的操作，如果它退出，将再次询问是否继续选择其他操作。我的问题是它没有在if语句中执行循环，而是执行循环，用户通过选择其他操作来要求继续。

import java.util.Scanner;

public class calculator
{





public static void main(String [] args)
{
    Scanner input = new Scanner (System.in);
    double x, y;
    double operation;
    String getChar;
    String chooseOperation;

    do
    {   
        System.out.println("Choose your operation:");
        System.out.println("A. Addition");
        System.out.println("B. Subraction");
        System.out.println("C. Multiplication");
        System.out.println("D. Division");

        chooseOperation = input.nextLine();

        if ((chooseOperation.equals("A")) | (chooseOperation.equals("a")))
        {
            do
            {
                System.out.println("You Choose Addition\n\n\n");
                System.out.println("Input the first number:\n");
                x = input.nextDouble();
                System.out.println("Input the second number:\n");
                y = input.nextDouble();
                operation = x+y;
                System.out.println("The sum is :"+operation);

                System.out.println("Continue?");
                System.out.println("Y/N");
                getChar=input.nextLine();
            }while(getChar.equals("Y"));
        }

        else if ((chooseOperation.equals("B")) | (chooseOperation.equals("b")))
        {
            do
            {
                System.out.println("You Choose Subtraction\n\n\n");
                System.out.println("Input the first number:\n");
                x = input.nextDouble();
                System.out.println("Input the second number:\n");
                y = input.nextDouble();
                operation = x-y;
                System.out.println("The difference is :"+operation);

                System.out.println("Continue?");
                System.out.println("Y/N");
                getChar=input.nextLine();
            }while(getChar.equals("Y"));
        }

        else if ((chooseOperation.equals("C")) | (chooseOperation.equals("c")))
        {
            do
            {
                System.out.println("You Choose Multiplication\n\n\n");
                System.out.println("Input the first number:\n");
                x = input.nextDouble();
                System.out.println("Input the second number:\n");
                y = input.nextDouble();
                operation = x*y;
                System.out.println("The product is :"+operation);

                System.out.println("Continue?");
                System.out.println("Y/N");
                getChar=input.nextLine();
            }while(getChar.equals("Y"));
        }

        else if ((chooseOperation.equals("D")) | (chooseOperation.equals("d")))
        {
            do
            {
                System.out.println("You Choose Division\n\n\n");
                System.out.println("Input the first number:\n");
                x = input.nextDouble();
                System.out.println("Input the second number:\n");
                y = input.nextDouble();
                operation = x/y;
                System.out.println("The quotient is :"+operation);

                System.out.println("Continue?");
                System.out.println("Y/N");
                getChar=input.nextLine();
            }while(getChar.equals("Y"));
        }
        else
        {
            System.out.println("Invalid Selection!\n\n\n");
        }
        System.out.println("Do you want to continue?\n\nY/N");
        getChar=input.nextLine();
    }while((getChar.equals("Y"))|(getChar.equals("y")));

}    
}

Answer 1

每次阅读整行，然后解析为double：

          //Addition
          do
            {
                System.out.println("You Choose Addition\n\n\n");
                System.out.println("Input the first number:\n");
                x = Double.parseDouble(input.nextLine());//read the whole line, then parse into double
                System.out.println("Input the second number:\n");
                y = Double.parseDouble(input.nextLine());//read the whole line, then parse into double
                operation = x + y;
                System.out.println("The sum is :" + operation);

                System.out.println("Continue?");
                System.out.println("Y/N");
                getChar = input.nextLine();//when not reading the whole line, getChar is empty
            }
            while (getChar.equals("Y"));

否则，getChar似乎包含用户输入数字时创建的下一行字符（键入数字然后按Enter键）。

Answer 2

很久以前我编写了java。但我认为这是因为你只使用了一个|。我不确定，但我认为java需要两个|。所以你的第一个将是：

if (chooseOperation.equals("A") || chooseOperation.equals("a"))
{

}

在java中嵌套do while循环

2 个答案: