This blog post is not about internals of JDK(Java Development Kit), But a mere documentation for people who want to get started. JDK is open sourced a long time ago. The reference implementation of Java is now based on OpenJDK. So any one interested in it can get the source code and play with it. Here on, when I refer to JDK it means all the components including Java class libraries/JVM(Hotspot)/Java Compiler. In this post, I will walk you in getting and building the latest JDK 9 sources.