Is there a better way to combine two string sets in java?

I need to combine two string sets while filtering out redundant information, this is the solution I came up with, is there a better way that anyone can suggest? Perhaps something built in that I overlooked? Didn't have any luck with google.

Set<String> oldStringSet = getOldStringSet();
Set<String> newStringSet = getNewStringSet();

for(String currentString : oldStringSet)
{
    if (!newStringSet.contains(currentString))
    {
        newStringSet.add(currentString);
    }
}