控制台不打印存储在通过方法调用的变量中的整数

Question

程序提取数字，我希望它继续循环，直到用户键入键“Q”/“q”。例如，当用户按下“O”键时，程序应该打印他们输入的数字的个位数字，以此类推用户输入的任何 3 位数字。我已经创建了提取个位、十位和百位数字的方法，并将它们存储到一个单独的类中的变量中，但是当我尝试打印这些数字时，控制台中没有打印任何内容。

import java.util.Scanner;

class Methods { 

public Methods (int value) {}

public int hundreds (int num) {
    int hund = (num /100)%10;
    return hund;
}

public int tens (int num) {
    int ten = (num / 10)%10;
    return ten;
}

public int ones (int num) {
    int one = num % 10;
    return one;
}
}


public class DigitExtractor {


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



    char input = ' '; //initialize outside loop
    Scanner s = new Scanner(System.in);


    System.out.print("Input an integer");
    int wholeNumber = s.nextInt();
    Methods num = new Methods(wholeNumber);


    do {
        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.println("Enter your choice: ");
        input = s.next().trim().charAt(0); //using scanner only


        if (wholeNumber == 'W' || wholeNumber == 'w') {
            System.out.println("The whole number is: " + wholeNumber);
        } else if (wholeNumber == 'O' || wholeNumber == 'o') {
            System.out.println("The ones place digit is: " + num.ones(wholeNumber));
        } else if (wholeNumber == 'T' || wholeNumber == 't') {
            System.out.println("The tens place digit is: " + num.tens(wholeNumber));
        } else if (wholeNumber == 'H' || wholeNumber == 'H') {
            System.out.println("The hundreds place digit is: " + num.hundreds(wholeNumber));
        }
    } while ((wholeNumber != 'q') && (wholeNumber != 'Q'));
}

}

Answer 1

您的代码有一些问题需要解决才能正常工作：

• Method 类必须在 DigitExtractor 类之外。
• 您在循环中调用的方法属于Methods 类，因此 你必须实例化的构造函数是Methods。
• 您必须从变量input 中捕获键盘输入。
• 额外：您需要用 try/catch 包围您的代码。

我对您的代码进行了最少的更正，它适用于这个版本：

import java.util.Scanner;

public class DigitExtractor {

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

        try (Scanner input = new Scanner(System.in)){

            System.out.print("Input an integer");
            int integer = input.nextInt();
            Methods num = new Methods(integer);
            char keyboard;

            do {
                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.println("Enter your choice: ");
                keyboard = input.next().charAt(0);

                if (keyboard == 'W' || keyboard == 'w') {
                    System.out.println("The whole number is: " + integer);
                } else if (keyboard == 'O' || keyboard == 'o') {
                    System.out.println("The ones place digit is: " + num.ones(integer));
                } else if (keyboard == 'T' || keyboard == 't') {
                    System.out.println("The tens place digit is: " + num.tens(integer));
                } else if (keyboard == 'H' || keyboard == 'H') {
                    System.out.println("The hundreds place digit is: " + num.hundreds(integer));
                }
            } while ((keyboard != 'q') && (keyboard != 'Q'));
        }
    }
}

class Methods { 

    public Methods (int value) {}

    public int hundreds (int num) {
        return (num /100)%10;
    }

    public int tens (int num) {
        return (num / 10)%10;
    }

    public int ones (int num) {
        return num % 10;
    }
}