Question

我似乎无法理解如何使用while循环来确定数字是否为正。在（I> 0）时，如果我输入任何正数，则结果总是大于0，这意味着存在无限循环。

int i = 0;

System.out.println("#1\n Input Validation\n Positive values only"); // #1 Input Validation
System.out.print(" Please enter a value: ");

Scanner scan = new Scanner(System.in);
i = scan.nextInt();

while (i > 0)
{
    System.out.println("The value is: " +i);
} 

System.out.println("Sorry. Only positive values.");

此外，当我输入一个负数时，它不会返回扫描仪以可能输入一个正数。

Answer 1

我相信这就是您要实现的目标。

    int i = 0; // int is 0

    while (i <= 0) {
        // int is 0 or a negative number
        System.out.println("#1\n Input Validation\n Positive values only");
        System.out.print(" Please enter a value: ");
        Scanner scan = new Scanner(System.in);
        i = scan.nextInt();

        if (i > 0) {
            System.out.println("The value is: " + i);
        } else {
            System.out.println("Sorry. Only positive values.");
        }
        // if number is positive then continue to termination. If negative then repeat loop
    }

请更加注意您放置while循环的位置，因为初始放置肯定会导致无限循环

while (i > 0)
{
    System.out.println("The value is: " +i);
    // number is positive - repeat loop containing only this line of code to infinity
}
// number is either 0 or negative so continue to termination

Answer 2

您可以采用这种方法：

    int i = 0;

    System.out.println("#1\n Input Validation\n Positive values only"); // #1 Input Validation

    Scanner scan = new Scanner(System.in);

    while (i >= 0) {
        System.out.print(" Please enter a value: ");
        i = scan.nextInt();
        if (i > 0) {
            System.out.println("The value is: " + i);
        } else {
            break;
        }
    }

    System.out.println("Sorry. Only positive values.");

使用扫描仪输入和正负号的“ while”无限循环

2 个答案: