Java Code for permutations of a list of numbers

Question

I have written a program to find all the possible permutations of a given list of items. This precisely means that my program prints all possible P(n,r) values for r=0 to n<

Answer 1

If you want all permutations of 15-ish or more elements, write them to disk or a db or something, since they won't fit in memory. Edit: Steinhaus–Johnson–Trotter algorithm. This is probably what you're looking for.