While Java feels like a static language, modern JVMs are actually quite dynamic. Classes can be loaded, inspected, and even modified at runtime. We will use Java's instrumentation framework and the ASM bytecode library to see what programs are really up to -- how they're using resources, where they're sending information, and so forth. You will learn all about Java bytecode and how JVMs work in general. By the end of this course, you should have the expertise needed to write Java agents for a variety of purposes.