Dynamically typed languages essentially have something like Java's Object type as the type of everything. Using wide types like that and interfaces in Java, you easily have dynamic traits in your code.

Static vs dynamic is actually kind of a blurry line: https://en.wikipedia.org/wiki/Strong_and_weak_typing

The dynamic its of Java are not its type system, they're things like late dynamic linking.

you can do metaprogramming - invent new methods or class on the run