控制台不打印存储在通过方法调用的变量中的整数

Question

该程序提取数字，我希望它一直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，对于用户输入的任何 3 位数字，依此类推。我已经创建了提取个位、十位和百位数字的方法，并将它们存储到单独类中的变量中，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使其正常工作：

• 班级Method必须在班级之外DigitExtractor。

• 您在循环中调用的方法属于该类Methods，因此您必须实例化的构造函数是Methods.

• 您必须从变量中捕获键盘输入input。

• 额外：你需要用 try/catch 包围你的代码。

我对您的代码进行了最少的更正，并且它适用于此版本：

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;

    }

}