java - 程序需要一直循环直到键入键 "Q"/"q"

Question

程序提取数字，我希望它继续循环，直到用户键入“Q”/“q”键。例如，当用户按下“O”键时，程序应打印他们输入的数字的个位数，对于用户输入的任何 3 位数字，依此类推。当我现在运行代码时，没有输出，但也没有错误。

import java.util.Scanner;
public class DigitExtractor {

    public static void main(String[] args) 
            throws java.io.IOException{

        char input;
        input = (char) System.in.read();
        Scanner s = new Scanner(System.in);

        variables Num = new variables();

        do {

            System.out.print("Enter an integer: ");
            String wholeNumber = s.nextLine();

            Num.ones = wholeNumber.charAt(2);
            Num.tens = wholeNumber.charAt(1);
            Num.hundred = wholeNumber.charAt(0);

            System.out.println("show (W)hole number.");
            System.out.println("show (O)nes place number.");
            System.out.println("show (T)ens place number.");
            System.out.println("show (H)undreds place number.");

            input = (char) System.in.read();
            System.out.println("Enter your choice: " + input);

            if(input == 'W' || input == 'w') {
                System.out.println(Num.WholeNum);
            }
            else if(input == 'O' || input == 'o') {
                System.out.println(Num.ones);
            }
            else if(input == 'T' || input == 't') {
                System.out.println(Num.tens);
            }
            else if(input == 'H' || input == 'H') {
                System.out.println(Num.hundred);

            }
        } while (input == 'q');
    }
}

class variables {
    char hundred; 
    char tens; 
    char ones;
    char WholeNum;
}

Answer 1

阅读变得困惑。为了使用扫描仪读取整数，我选择了 nextInt。这很有帮助。我同意你的方法，不要将事情分解成更小的 block 。并且(修订)我仅使用扫描仪进行读取，甚至是选择的字符。我还在您必须按下选项之前添加了提示，以便您知道。

       public static void main(String[] args)


 throws java.io.IOException {
       int hundred; //my compiler was fussy about having the extra class
       int tens;
       int ones;
       char input = ' '; //initialize outside loop
       Scanner s = new Scanner(System.in);



   do {

       System.out.print("Enter an integer: ");
       int wholeNumber = s.nextInt();

       ones = wholeNumber % 10;
       tens = (wholeNumber / 10) % 10;
       hundred = (wholeNumber / 100) % 10;

       System.out.println("show (W)hole number.");
       System.out.println("show (O)nes place number.");
       System.out.println("show (T)ens place number.");
       System.out.println("show (H)undreds place number.");
       System.out.println("(Q)uit");
       System.out.print("Enter your choice: ");
       input = s.next().trim().charAt(0); //using scanner only
       //System.out.println("Enter your choice: " + input);

       if (input == 'W' || input == 'w') {
           System.out.println(wholeNumber);
       } else if (input == 'O' || input == 'o') {
           System.out.println(ones);
       } else if (input == 'T' || input == 't') {
           System.out.println(tens);
       } else if (input == 'H' || input == 'H') {
           System.out.println(hundred);

       }
   } while ((input != 'q') && (input != 'Q'));


}

   }