I thought I’d drop this in here in case anyone ran into this, because this error is so obscure!
$ javac PrimeDirective.java Note: PrimeDirective.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details.
I ran into this in the PrimeDirective exercise, which was tripping me up. It has to do with:
ArrayList<Integer> primes = new ArrayList();
The issue here was that I wasn’t specifying the type in the instantiation. It should be:
ArrayList<Integer> primes = new ArrayList<Integer>();
Types always mess me up!