Java: Generate a number based on percent chances / frequencies

I would like to make this program which takes two arrays, one of which contains the choices and one of which contains the frequencies out of based on 5000 occurrences. The part that I am having trouble with is actually using these frequencies to get the number. I originally used the Random class, but I decided that it is not completely random, so I wrote a csv file. Is there any way to do this or is this a lost cause?