Factorials

Do this project in the lab.

The factorial of n (written n!) is the product of the integers between 1 and n. Thus 4! = 1*2*3*4 = 24. By definition, 0! = 1. Factorial is not defined for negative numbers.

1. Write a program, Fact.java, that asks the user for a non-negative integer and computes and prints the factorial of that integer. You'll need a while loop to do most of the work -- this is a lot like computing a sum, but it's a product instead. And you'll need to think about what should happen if the user enters 0.
   1. Don't start writing code right away. Think first! Get out a paper and pencil (or a text editor), and write out a pseudo-code for your proposed solution. Call an instructor to look at your pseudo-code before beginning to write your code. You must do this to obtain extra credit.
   2. Okay, now on to Eclipse: convert your pseudo-code into Java.
   3. Test your program with a couple of small numbers (3 and 7, say). Don't try numbers bigger than about 50 as the program will may terminate with an overflow.
2. Now modify your program so that it checks to see if the user entered a negative number. If so, the program should print a message saying that a nonnegative number is required and ask the user the enter another number. The program should keep doing this until the user enters a nonnegative number, after which it should compute the factorial of that number. Hint: you will need another while loop before the loop that computes the factorial (as you may have to prompt the user repeatedly until they enter a correct input). You should not need to change any of the code that computes the factorial!

Submit Fact.java. Copy a sample session of running the program into the lab document.