Thank you for being the rare question where you actually provide what language you want your answer in; I approve, and encourage this.
In Java, the following will work.
I made it a bit more versatile to work with others numbers, other than 99, if you so please (if not, just hardcode the 99 in yourself).
// Example list - fill this with numbers yourself.
ArrayList<Integer> nums = new ArrayList<>();
int n = 99;
int count = (int)nums.stream().filter(i -> i == n).count();
System.out.println(n + " occurences.");
