Question

I want to do exactly like this in java

Compare two string ArrayLists

the accepted answer is perfect.. ‘Except’ method… is there a equivalent of this in Java …
sure there isn’t in standard Java lib, but is there something in third party libs like apache ?

P.S I googled this .. coudn’t find anything

Answer 1

You want to find the elements of list a that are not present in list b.

How about:

a.removeAll(b);

That will remove all elements of b from a. Whatever’s left in a is by definition something that wasn’t in b.

If you can’t or don’t want to change a, copy it and do the removeAll() on the copy.

And more generally, if your collection class in Java doesn’t support removeAll(), then create a collection type that does support it from a and do the remove on that new object.

If the lists are large, you’ll probably want to create a HashSet from a for example, so the removals (i.e. the internal lookup part of doing a removal) can happen more efficiently than for a List subtype.