java-basics: What is the Java Classloader?

Java Classloader is the part of the Java runtime environment that loads classes on demand (lazy loading) into the JVM (Java Virtual Machine). Classes may be loaded from the local file system, a remote file system, or even the web.

When the JVM is started, three class loaders are used:

1. Bootstrap Classloader: Loads core java API file rt.jar from folder.
2. Extension Classloader: Loads jar files from folder.
3. System/Application Classloader: Loads jar files from path specified in the CLASSPATH environment variable.