java - isDigit 验证

Question

我正在尝试验证 1 或 2 的输入。但是，使用此代码，如果您输入字母，则会导致程序崩溃。

如何解决这个问题？

System.out.print("Choice: ");
userSelection  = keyboard.nextInt();

while (flag == 0)
{
    if (userSelection == 1 || userSelection == 2)
    {
        flag = 1;
    }
    if(Character.isDigit(userSelection))
    {
        flag = 1;
    }
    else 
    {
        flag = 0;
    }
    if (flag == 0)
    {
        //this is a system clear screen to clear the console
        System.out.print("\033[H\033[2J");  
        System.out.flush(); 

        //display a warning messege that the input was invalid
        System.out.println("Invalid Input! Try again, and please type in selection 1 or selection 2 then hit enter");
        System.out.print("Choice: ");
        userSelection  = keyboard.nextInt();
    }
}

Answer 1

nextInt 期望用户输入一个整数。否则将会失败。

您可能想要使用 nextLine 构造一些内容(它读取一行输入，然后您可以检查它， reading single characters as they are being typed is tricky in Java )。