Understanding when a class is loaded and initialized in JVM is one of the fundamental concepts of Java programming language. Thanks to Java language specification we have everything clearly documented and explained, but many Java programmer still doesn't know when a class is loaded or when a class is initialized in Java. Classloading and initialization seems confusing and complex to many beginners and its true until having some experience in belt its not always easy to get into subtle details of How JVM works in Java. In this Java tutorial, we will see when class loading occurs in Java and when and how class and interface are initialized in Java.