not sure if I am asking this correctly, but does anyone know if List and List would hold different amount of memory space for one-character elements, that is, character elements or strings with only one character each?

The java code below is a solution to a problem in Hackerrank – a simple text editor with 4 operations (append, delete, print, undo). However, for a few of the test cases it exceeds the time limit. How can I optimize it more.