code: public static String locate(String className, ClassLoader classLoader) {
          String resource = new String(className);
  
          // format the file name into a valid resource name
          if (!resource.startsWith("/")) {
              resource = "/" + resource;
          }
          resource = resource.replace('.', '/');
          resource = resource + ".class";
  
          // attempt to locate the file using the class loader
          URL classUrl = classLoader.getResource(resource);
          if (classUrl == null && classLoader == ClasspathUtil.class.getClassLoader()) {
              // Apparently clazz.getResource() works sometimes when clazz.getClassLoader().getResource() does not.
              // TODO: why?
              classUrl = ClasspathUtil.class.getResource(resource);
          }
  
          if (classUrl == null) {
              return "\nClass not found: [" + className + "]";
          }
          else {
              return classUrl.getFile();
          }
      }
docs: Finds the location of the version of a particular class that will be used
  by the Java runtime. Output goes to standard out.
  
  @param className
  @return whether the class was located