katamari | mass spectrometry proteomics analysis pipeline | Genomics library

Here's a solution in JavaScript - you can follow the logic and the hopefully apply the concepts to your Java project. There's a running demo in this Plunkr https://plnkr.co/edit/KcHh63ou25LZDaZ79iwI?p=preview

Basically what we're doing is creating an initial array of all the possible questions, and an empty array of questions we're going to include on the quiz. We decide how many questions to include, in this example 5, and then loop that number of times.

On each iteration, we get the current length of the array holding all the possible questions, and pick a random number between 0 and the number of questions left in the array, then we push the question at that index value onto our array of quiz questions, and slice that question out of our array of possible questions so it's not there to get picked a second time.

Then we iterate again, now the source question array is one shorter, we get it's new length, pick a new random number and grab that question, add it to our quiz array, slice it out of our source questions array.

Lather, rinse, repeat.