Does use of final keyword in Java improve the performance?

Question

In Java we see lots of places where the final keyword can be used but its use is uncommon.

For example:

String str = \"abc\";
System.ou         


        

Answer 1

Final (At least for member variables and parameters) is more for humans then it is for the machine.

It's good practice to make variables final wherever possible. I wish Java had made "variables" final by default and had a "Mutable" keyword to allow changes. Immutable classes lead to much better threaded code, and just glancing at a class with "final" in front of each member will quickly show it to be immutable.

Another case--I've been converting a lot of code to use @NonNull/@Nullable annotations (You can say a method parameter must not be null then the IDE can warn you every place you pass a variable that isn't tagged @NonNull--the whole thing spreads to a ridiculous degree). It's much easier to prove a member variable or parameter can't be null when it's tagged final since you know it's not being re-assigned anywhere else.

My suggestion is to get in the habit of applying final for members and parameters by default, It's just a few characters but will nudge you towards improving your coding style if nothing else.

Final for methods or classes is another concept since it disallows a very valid form of reuse and doesn't really tell the reader much. The best use is probably the way they made String and the other intrinsic types final so you could rely on consistent behavior everywhere--That prevented a lot of bugs (although there are times I would have LOVED to extend string.... oh the possibilities)