DigitUtil.java

public class DigitUtil {

    public static boolean isSingleDigit(int x) {
        if (x > -10 && x < 10) {
            return true;
        } else {
            return false;
        }
    }

    public static boolean isSingleDigit2(int x) {
        return x > -10 && x < 10;
    }

    public static void main(String[] args) {
        System.out.println(isSingleDigit(2));
        boolean bigFlag = !isSingleDigit(17);

        int z = 9;
        if (isSingleDigit(z)) {
            System.out.println("z is small");
        } else {
            System.out.println("z is big");
        }
    }

}