Question

I have two ArrayList. Each is of size 100000. I want to compare them and count matched elements.

Here’s my code:

for (int i = 0; i < mArryLst2.size(); i++) {
   if (ArryLst1.contains(mArryLst2.get(i))) {
       matchedPixels++;         
   }
}

Here comparison process is taking lot of time.

How to solve and optimize this problem.

Answer 1

you should use CollectionUtils.retainAll : Returns a collection containing all the elements in collection1 that are also in collection2.

ArrayList commonList = CollectionUtils.retainAll(list1,list2);