Almost all well-known object oriented languages (Java, C#, JavaScript, Python, Ruby, ...) have single dispatch: Methods are chosen depending on the (single) receiver of a message. On the other hand, there is multiple dispatch which is an interesting mix of functional method selection with mutable state. It is used in less-known object-oriented languages such as Common Lisp.

In this article, we'll first look at Java's single dispatch and Java's overloading and then use what we have learned to understand multiple dispatch and how it solves some design dilemmas that can't be solved with single dispatch.