If a String is immutable, then why do you have to call a method to get the length instead of just accessing a variable, like array.length?

Question

It seems to me that calling string.length() each time takes significantly longer than just accessing a variable.

Answer 1

String implements interface CharSequence, which in turn defines length method. You couldn't do the same with variables since variables can't be abstract or overridden.
As other people say, Java is using interfaces heavily.