23. deftype and definterface
Published 19 January 17
Clojure is built on a well thought out set of abstractions. To implement these, it makes use of the ability to define abstractions in the host language, namely Java interfaces, and the high-performance polymorphism that they provides.
As a Clojure programmer you don’t have to resort to Java to achieve the same thing. All the facilities are there to create interfaces, and to create types that implement interfaces, getting you as close to the JVM as you need to be.