What is the best way to iterate over multiple lists in the same method in Java

Question

I need to achieve a result that give me 4 different sums after iterate over lists in a single method in Java.

I have 4 different lists with a lot of entries, and i need to iterate in the same way over those 4 lists. Whats the best way to do it, and maintain the best possible performance. Should i implement some Thread Pool? or does not really matter? The lists have around 500 entries each.

Thank you.

Answer 1

Cleanest way I can think of:

IntStream
  .range(0,4)
  .parallel()
  .foreach(i -> 
    lists[i]
    .stream()
    .parallel()
    .forEach(item -> operation(item)))