[evanspa]

Java has always allowed for class members using the "static" keyword.

The GoF book predates the public release of Java. The code samples in GoF are in C++ and Smalltalk.

Correct me if I'm wrong, but Java 8 does allow functions to be passed around. E.g., if a function takes as input a Runnable, I can pass a no arg lambda expression as input.

[gozur88]

There are actually a bunch of different kinds of functions you can use in lambda expressions in Java 8 (43, to be exact).

https://www.tutorialspoint.com/java8/java8_functional_interf...

Beyond that, by at least 1.4 you could pass methods using the reflections API, though that was kludgy in a lot of ways.