The Bootstrap classloader is the parent of all classloaders and loads the standard JDK classes in lib directory of JRE (rt.jar and i18n.jar). All the
java.* classes are loaded by this classloader.
The Extensions Classloader is the immediate child of the Bootstrap classloader. This classloader loads the classes in
lib\ext directory of the JRE.
The System-Classpath classloader is the immediate child of the Extensions classloader. It loads the classes and jars specified by the
CLASSPATH environment variable
You could try to inject your custom class loader by means of the
java.system.class.loader property (see ClassLoader#getSystemClassLoader).
The Default System class loader is the parent for MyClassLoader instances.