docs: private Class<?> loadClass(final String classname) throws PluginException {
          if (null == classname) {
              throw new IllegalArgumentException("A null java class name was specified.");
          }
          if (null != classCache.get(classname)) {
              return classCache.get(classname);
          }
          CachedJar cachedJar1 = getCachedJar();
  
          debug("loadClass! " + classname + ": " + cachedJar1.getCachedJar());
          final Class<?> cls;
          final URLClassLoader urlClassLoader = cachedJar1.getClassLoader();
          try {
              cls = Class.forName(classname, true, urlClassLoader);
              classCache.put(classname, cls);
          } catch (ClassNotFoundException e) {
              throw new PluginException("Class not found: " + classname, e);
          } catch (Throwable t) {
              throw new PluginException("Error loading class: " + classname, t);
          }
          return cls;
      }