Given a String str and an int n, return true or false if the first n characters of str are the same as
the last n characters of the same String. The String will always be at least n characters long so no need to
worry about funny sizes.
Example code runs (do NOT code for these examples - it won't always be these values):
dejaVu("can can", 3) -> true
dejaVu("kayak", 2) -> false
dejaVu("do you know what to do", 2) -> true
public boolean de JaVu (String str, int n) {