For example, we may want to list the classes from one of the packages of the current application (for example, the modern.challenge package) or the classes from one of the packages from our compile-time libraries (for example, commons-lang-2.4.jar).
Classes are wrapped in packages that can be archived in JARs, though they don't have to be. In order to cover both cases, we need to discover whether the given package lives in a JAR or not. We can do this by loading the resource via ClassLoader.getSystemClassLoader().getResource(package_path) and checking the returned URL of the resource. If the package doesn't live in a JAR, then a resource will be a URL starting with the file: scheme, as in the following example ...
