Question

Here are two method declaration:

def fun = "x"

def fun() = "x"

Since they both need no parameter and return a String, what’s the difference besides invoking way?

Answer 1

It’s just a convention:

obj.fun   //accessing like property with no side-effects

obj.fun() //ordinary method call, return value, but might also have side-effects 

Prefer () version to emphasize that this is a method as opposed to simple property.

Note that this is just a convention, a way to document code, the compiler does not enforce the rules above.