# Welcome to Day 4

Today we will look at two main topics:

* Concurrency: threads, channels, shared state, `Send` and `Sync`.

* Android: building binaries and libraries, using AIDL, logging, and
  interoperability with C, C++, and Java.

> We will attempt to call Rust from one of your own projects today. So try to
> find a little corner of your code base where we can move some lines of code to
> Rust. The fewer dependencies and "exotic" types the better. Something that
> parses some raw bytes would be ideal.