Eta is a pure, lazy, strongly-typed functional programming language on the JVM. Java is an impure object-oriented programming language. The selling point of a JVM language is that you are able to use a vast ecosystem of existing libraries without having to re-invent the wheel. How do we make these two seemingly incompatible programming paradigms work with each other? In this talk, we will discuss Eta's Foreign Function Interface (FFI), a mechanism with provides a type-safe way to interact with the Java ecosystem while maintaining the purity property. It also has support for handling Java's inheritance, generics, and even allows you to use an Eta function to implement a Java Single Abstract Method (SAM) type. This allows you to easily import Java methods into your programs without knowing the internals of Java and also export your Eta functions into a form that Java can understand.