The class loader to load classes, native libraries and resources from the top JAR and from JARs inside the top JAR. The top JAR very often is referred as an executable, standalone or uber JAR. The class loader looks through the hierarchy of JARs and allows nested JARs. The class loader delegates class loading to the parent class loader and successfully loads classes, native libraries and resources when it works not in a JAR environment. Taken from http://www.jdotsoft.com/JarClassLoader.php, see there for more information.