how to add method to standard java class

Question

Is there a way to add a method to a standard Java class, such as Object?

I know you can't subclass classes like String which are final, but Object isn't. I know I could just subclass Object and define a method in the subclass and make all my classes subclasses of that, but I'd rather not have to do that.

I suspect that this is either impossible or I've overlooked something. Thanks in advance for any answers.

Answer 1

You can't do this in Java. But other JVM languages are capable of doing so:

• in groovy ExpandoMetaClass allows adding arbitrary methods to any class

• in scala implicit conversions can be used to emulate such behaviour in statically-typed manner, see: Inject methods into existing classes

• also you can run ruby (jruby) and javascript on top of JVM