When do you use Java's @Override annotation and why?

Answer 1

If you find yourself overriding (non-abstract) methods very often, you probably want to take a look at your design. It is very useful when the compiler would not otherwise catch the error. For instance trying to override initValue() in ThreadLocal, which I have done.

Using @Override when implementing interface methods (1.6+ feature) seems a bit overkill for me. If you have loads of methods some of which override and some don't, that probably bad design again (and your editor will probably show which is which if you don't know).

Answer 2

I use it every time. It's more information that I can use to quickly figure out what is going on when I revisit the code in a year and I've forgotten what I was thinking the first time.

Answer 3

Override annotation is used to take advantage of the compiler, for checking whether you actually are overriding a method from parent class. It is used to notify if you make any mistake like mistake of misspelling a method name, mistake of not correctly matching the parameters

Answer 4

@Override on interface implementation is inconsistent since there is no such thing as "overriding an interface" in java.

@Override on interface implementation is useless since in practise it catches no bugs that the compilation wouldn't catch anyway. There is only one, far fetched scenario where override on implementers actually does something: If you implement an interface, and the interface REMOVES methods, you will be notified on compile time that you should remove the unused implementations. Notice that if the new version of the interface has NEW or CHANGED methods you'll obviously get a compile error anyways as you're not implementing the new stuff.

@Override on interface implementers should never have been permitted in 1.6, and with eclipse sadly choosing to auto-insert the annotations as default behavior, we get a lot of cluttered source files. When reading 1.6 code, you cannot see from the @Override annotation if a method actually overrides a method in the superclass or just implements an interface.

Using @Override when actually overriding a method in a superclass is fine.

Answer 5

I use it everywhere. On the topic of the effort for marking methods, I let Eclipse do it for me so, it's no additional effort.

I'm religious about continuous refactoring.... so, I'll use every little thing to make it go more smoothly.

Answer 6

It does allow you (well, the compiler) to catch when you've used the wrong spelling on a method name you are overriding.