Common programming mistakes for Clojure developers to avoid [closed]

Answer 1

too many parantheses, especially with void java method call inside which results in NPE:

public void foo() {}

((.foo))

results in NPE from outer parantheses because inner parantheses evaluate to nil.

public int bar() { return 5; }

((.bar)) 

results in the easier to debug:

java.lang.Integer cannot be cast to clojure.lang.IFn
  [Thrown class java.lang.ClassCastException]