This challenge is an application of java.math that allows unlimited precision calculations. The primary reference sites are Java Math, Java BigDecimal, and Java BigInteger.

The usage of BigDecimal function multiply will be essential.

Java Math tutorial: (Simplified summary that is believed correct)

vd-decimal value, vstr-string, vi-integer value 
xBD=java.math.BigDecimal(vd);  % valid vd,vstr,vi creates xBD a BigDecimal variable
import java.math.*;  % simplifies statements
xBD=BigDecimal(vstr);

xmultiplyzBD=xBD.multiply(BigDecimal(z));  % multiply input requires BD type

To convert java to string of unlimited length can be achieved via java toString or Matlab char

xstr=toString(xBD)  or xstr=char(xBD) 

Input: N [1< N < 1000]

Output: Y (char variable of Y=N! or a BigDecimal variable)

Factorial Calculator

Related Challenges:

1. Usage of java math

2. nchoosek_large (full precision)
2. Next Prime
3. factor_large
4. Factorial