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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.

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  • You can't add method to standard java class. Commented Aug 26, 2012 at 12:54
  • Well you should do that! The behaviour you are expecting is in Javascript prototypes. Commented Aug 26, 2012 at 12:55
  • Is this for testing or production code? Commented Aug 26, 2012 at 13:03
  • Could you explain why you'd possibly want to do this? Commented Aug 26, 2012 at 13:17
  • Yes I imamgined it was impossible in Java. Initially it is for doing some experiments but if I can get other stuff to go with it to work it would hopefully end up in some OSS software. There are really two reasons I was hoping to add a method to Object. One is because logically it is the best way for other reasons. The other reason is that the method(s) I have in mind crucially rely on the this keyword. However, see below. Commented Aug 26, 2012 at 19:54

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

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Thanks for the answer. Yes I thought one of the JVM scripting languages might be able to do it. This is acceptable to me. What I should have said is that I wanted a JVM solution (not necessarily Java) so one of the dynamic JVM languages or using reflect or even using a customised Object class file in the classpath would be okay. I'll look at groovy and javascript for sure. However I thought an "in-language" solution would be best from a maintenance perspective. Thanks Tomasz for the answer to all who commented.

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