Throughout its history, the Java language has played an industry-leading role in the tricky business of specifying the behavior of concurrent programs. This is an area in which a down-to-the-metal understanding can help developers strike the right balance between safety and performance, so we'll start by motivating the discussion with counterintuitive low-level examples. We'll describe the Java Memory Model as a basis for solutions and touch on how C, C++, and C# deal with the same issues. This material can help any developer gain insight into their code. Be there or be unsynchronized!