Edge case: Digits of a number
A common programming exercise involves taking the digits of an integer and rearranging them in some way. The fastest
way to get the last digit of an integer is to use modulo 10 (% 10). This returns the remainder when dividing the
integer by 10.
Here is a method that returns the last digit of an integer. The method fails for exactly half of all possible inputs, negative numbers. This is because modulo 10 preserves the integer's sign.
Input an integer value that causes the lastDigit() method to return an incorrect value.
This exercise is part of the course
Introduction to Testing in Java
Exercise instructions
- Write a multi-digit integer whose last digit is not correctly identified by the
lastDigit()method.
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
public class LastDigit {
public static void main(String[] args) {
// Write down an integer that causes an incorrect return value of lastDigit()
int n = ____;
System.out.println("The last digit of " + n + " equals " + lastDigit(n) + ".");
}
public static int lastDigit(int a) {
return a % 10;
}
}