Question

如何输入0到9之间的键盘编号？

public static void main(String[] args) {
    int cars;
    if (cars > 0 && cars < 9) {
        Scanner sc = new Scanner(System.in);
        cars = sc.nextInt();
    }
    System.out.println("Saisissez un entier : " + cars);
}

Answer 1

首先，您必须阅读数字，然后检查数字是否在0到9之间

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int cars = sc.nextInt();

    if (cars >= 0 && cars <= 9) {
        System.out.println("Saisissez un entier : " + cars);
    }
}

Answer 2

也许使用while循环可能会有所帮助：

import java.util.Scanner;

class Main {

  public static void main(String[] args) {
    int userDigit = getSingleDigitIntegerInput();
    System.out.println("You entered: " + userDigit);
    // System.out.println("Saisissez un entier: " + userDigit);
  }

  private static int getSingleDigitIntegerInput() {
    Scanner scanner = new Scanner(System.in);
    String prompt = "Please enter a digit between 0 and 9 inclusive: ";
    int validDigit = -1;

    System.out.print(prompt);
    while (scanner.hasNext()) {
      if (scanner.hasNextInt()) {
        validDigit = scanner.nextInt();
        if (String.valueOf(validDigit).length() == 1) {
          scanner.close();
          break;
        } else {
          System.out.println("Error: Input number was too long");
          System.out.print(prompt);
        }
      } else {
        System.out.println("Error: Invalid input");
        System.out.print(prompt);
        scanner.next();
      }
    }

    return validDigit;
  }

}

用法示例：

Please enter a digit between 0 and 9 inclusive: a
Error: Invalid input
Please enter a digit between 0 and 9 inclusive: -1
Error: Input number was too long
Please enter a digit between 0 and 9 inclusive: 12345
Error: Input number was too long
Please enter a digit between 0 and 9 inclusive: 7
You entered: 7

Answer 3

您现在的问题是代码中事物发生的顺序。您首先声明一个可变汽车，但尚未赋予它任何价值然后检查汽车是否在0到9之间然后给汽车一个价值

您必须切换第2步和第3步，才能使逻辑正常工作

public static void main(String[] args) {
    int cars; //Step 1
    if (cars > 0 && cars < 9) { //Step 2
        Scanner sc = new Scanner(System.in); //Step 3
        cars = sc.nextInt(); //Step 3
    }
    System.out.println("Saisissez un entier : " + cars);
}

如何在Java中输入介于0和9之间的键盘编号

3 个答案: