A Comprehensive Introduction to Java Virtual Machine (JVM)

Note: You don't have to register for this course if you have already registered for my comprehensive Java course ~ Java In-Depth: Become a Complete Java Engineer!. The Java course includes all the content that is covered in this course. However, it is very likely that this course could be extended while the JVM related content in the Java course may not be extended any further.

To be a complete Java engineer, apart from having a strong background in Java & design patterns, it is also important to have a good understanding of the internal workings of Java Virtual Machine (JVM). Towards this end, this course is about helping you gain a solid understanding of how JVM works. Here is how the course is organized.

In section 1, we start off by discussing about why JVM (and Java) were created and then discuss JVM and it's architecture at a high-level. In the process, we will also take a look at how Just-in-time (JIT) compilation works.

Sections 2 - 4 delve into the real internals of JVM.

In section 2, we discuss the Lifetime of a Type, i.e., we look at what happens to a Class/Interface since the time it is accessed for the very first time. We learn when and how a class is loaded into memory (Class Loading), when classes it is referencing are loaded (Linking), and when its variables are initialized (Initialization). After conceptually introducing the process, everything will be demonstrated in code.

In section 3, we look at the Reflection API where we learn how to introspect (examine) other classes at runtime and even execute those classes. Frameworks like Spring and JUnit internally use reflection extensively. Knowing reflection is critical when we would have to build frameworks and tools that others use. This section includes a coding exercise where a basic unit testing framework is simulated using Reflection API.

In section 4, we look at the different memory areas (runtime data areas) that JVM deals with. Here we will learn about things like method area, heap, method table, garbage collection, stacks and we will also look at some of the Java bytecode instructions too. In one of the demos, we will look at how we can tune the heap size and how it impacts garbage collection process. To  learn about bytecode instructions, we will actually disassemble a .class file and we will inspect the bytecode instructions and learn about how they work.

The demo programs are available for download from the resources section of the corresponding lectures.

It is very likely that the course will also be updated to make it as comprehensive and as practical as possible.

Happy Learning.