Question

我有一个while循环。检查x介于两个值之间。现在我应该接受一个int值，但是如果用户输入double im获取异常。我如何在同一个if语句中包含一个检查，这样如果用户键入一个double，它将打印类似“x必须是10到150之间的int：”

            do {
            x = sc.nextInt();
            if ( x < 10 || x > 150 ) {
                System.out.print("x between 10 and 150: ");
            } else {
                break;
            }

Answer 1

您无需额外检查。例外就在那里，所以你可以在你的程序中采取相应的行动。毕竟，输入错误的方式并不重要。只是捕获异常（NumberFormatException，我猜？）并在捕获它时，打印一条错误消息：

while (true) try {
    // here goes your code that pretends only valid inputs can occur
    break;   // or better yet, put this in a method and return
} catch (NumberFormatException nfex) {  // or whatever is appropriate
    System.err.println("You're supposed to enter integral values.");
    // will repeat due to while above
}

Answer 2

您可以使用while (true)来捕获异常并处理它，以允许用户重试。

这是我的代码：

Scanner sc = new Scanner(System.in);
do {
    System.out.print("\nInsert a number >>> ");
    try {
        int x = sc.nextInt();
        System.out.println("You inserted " + x);
        if (x > 10 && x < 150) {
            System.out.print("x between 10 and 150: ");
        } else {
            break;
        }
    } catch (InputMismatchException e) {
        System.out.println("x must be an int between 10 and 150");
        sc.nextLine(); //This line is really important, without it you'll have an endless loop as the sc.nextInt() would be skipped. For more infos, see this answer http://stackoverflow.com/a/8043307/1094430
    }
} while (true);

Answer 3

public class SomeClass {                                                         
    public static void main(String args[]) {                                     
        double x = 150.999; // 1
        /* int x = (int) 150.999; */ // 2                                          
        if ( x >= 10 && x <= 150 ) { // The comparison will still work                                             
            System.out.print("x between 10 and 150: " + x + "\n");               
        }                                                                        
    }                                                                            
}

将x声明为double，double和int之间的比较仍然有效。
或者，转换数字，任何小数值都将被丢弃。

Java：如何测试输入是double还是int

3 个答案: