Exercise: Factorial

The factorial of a number is the product of all positive integers less than or equal to that number. For example:

factorial of 5: 5 * 4 * 3 * 2 * 1 = 120
factorial of 4: 4 * 3 * 2 * 1 = 24
factorial of 3: 3 * 2 * 1 = 6
factorial of 2: 2 * 1 = 2
factorial of 1: 1
factorial of 0: 1

Write a console program that lets the user choose a number between 0 and 19. Calculate the factorial of that number. If the user chooses a number smaller than 0 or larger than 19, print an error message.

Your program should produce output exactly like this (user input in green):

Enter a number to calculate its factorial. Your number must be between 0 and 19:
4
Factorial of 4: 24

As you can see, you need to print the user-entered number and the calculated factorial as the last line of your program's output. If the user enters a number that is not between 0 and 19, print an error message exactly like this:

Enter a number to calculate its factorial. Your number must be between 0 and 19:
-1
Your number (-1) is too small. It must be 0 or larger.

Another example:

Enter a number to calculate its factorial. Your number must be between 0 and 19:
20
Your number (20) is too large. It must be 19 or smaller.

Hand in instructions

Make sure your program runs correctly.
Follow Java naming conventions of variables.
Make sure your program is well-formatted.
Hand in your program by uploading Main.java to Moodle.