Merging two arrayLists into a new arrayList, with no duplicates and in order, in Java

Question

I am trying to \"combine\" two arrayLists, producing a new arrayList that contains all the numbers in the two combined arrayLists, but without any duplicate elements and the

Answer 1

Firstly remove duplicates:

arrayList1.removeAll(arrayList2);

Then merge two arrayList:

arrayList1.addAll(arrayList2);

Lastly, sort your arrayList if you wish:

collections.sort(arrayList1);

In case you don't want to make any changes on the existing list, first create their backup lists:

arrayList1Backup = new ArrayList(arrayList1);