如何验证用户输入是否在一定范围内？

Question

我编写了一个程序，它向用户询问 1-6 之间的数字字符串，并返回获得该字符串所用的掷骰数。我想验证输入，这样该人就不会输入大于 6 或小于 1 的数字，而且我似乎不知道该怎么做。

int SIDES = 6;
String userString = "null";
String answer = "null";
int length = 0;
do {
    do {
        System.out.print("please enter a string of 6 numbers you want to be rolled");
        userString = keyboard.next();
    while (length != SIDES) {
        System.out.println("please enter a valid string number");
        userString = keyboard.next();
    } 
        length = userString.length();
} while ( length != SIDES); // I want to add the validation to this line
dieRoll(userString);

Answer 1

while (length != SIDES) {
    userString = keyboard.next();
    try {
        int userStringNumber = Integer.parseInt(userString);
        if(userStringNumber<1||userStringNumber>6)
            throw new IllegalArgumentException();
    } catch (NumberFormatException e) {
        System.out.println("Please provide a number");
    }
    catch (IllegalArgumentException ex){
        System.out.println("Number should be between 1 and 6");
    }

}