Mistake Fixed

The loop condition is wrong. It was easy to find this problem since there is only one loop. Here is the fix:

while ( N >= 0 )

Here is a test run of the program after the fix:

C:\Source> javac FactorialTester.java
C:\Source> java FactorialTester
To exit, enter a negative value
Enter N: 0
factorial is 1
Enter N: 1
factorial is 1
Enter N: 7
factorial is 1
Enter N: 25
factorial is 1
Enter N: -1
C:\Source>