Best way to merge and remove duplicates from multiple lists in Java

Question

I have a situation where I will be receiving 2+ ArrayList and I need to be able to merge all the lists and remove any duplicate Widget so

Answer 1

Use Set Collection Class,

ArrayList mergeList = new ArrayList();
mergeList.addAll(widgets1);
mergeList.addAll(widgets2);
Set set  = new HashSet(mergeList);
ArrayList mergeListWithoutDuplicates = new ArrayList();
mergeListWithoutDuplicates .addAll(set);
return mergeListWithoutDuplicates;

Now here Set will remove all duplicates values from your ArrayList.