ArrayList of ArrayLists (dynamic 2D array) of custom class

Ok, but how would I “write back” that Element into the ArrayList so just “exampleString” gets changed and no other member variable?

Get it “out of the array” into a temporary variable, change only the things I want to change, then overwrite the “original” element in the array with the “updated” temporary variable, right?

And yes, I know that there is no [] to interface with arraylists here, I just used that to make it more “understandable” for everybody.
(Since the ArrayList thing obviously tries to be the “vector” we have in C++)