awesome, let's go 😃

Well first takeaway from page 5 : "Almost everything defined in a Clojure program can be redefined, even while the program is running: functions, multimethods, types, type hierarchies, and even Java method implementations."

How is it possible to redefine a Java method implementation?

I'm not 100% sure, but you could override the way in which clojure calls java code, and modify it at that point?

Disclamer: pure speculation

Does it mean you can provide your own version in clojure of some java implementation? Say override a string method?

@allouis: have a look here. Seemingly yes. http://stackoverflow.com/questions/25337983/extend-java-class-in-clojure-how-to-override-only-one-of-two-similar-methods

That is more overriding, which is different from redefining. Especially with Javas love of Factories - to redefine this method in Clojure would mean reimplementing all the surrounding code to make sure you create your new class..