Please help me code the following in: JAVA!

Please read the instructions THOROUGHLY and use many COMMENTS!

Full points will be awarded, thanks in advance!

5. Combinations, or "N Choose R'" Given a set of n items, how many ways can we pick r elements from n? This is known as the "choose function" (or binomial coefficient), and we can calculate the number of r-sized subsets of n (where order is unimportant) using the recurrence relationship defined below. Note that this definition builds on the notion of factorial, so make sure you understand the sample code first and have produced a working factorial method before moving on. You can create a faster solution to this problem if you reuse the individual component calculations (rather than re-calculating these), which are r! (less than n!) and (n-r)! (also less than n!), but this is merely an observation and not required to be implemented as part of the lab