code: protected static StringBuilder appendResourcePathPrefixFor(StringBuilder sb, Class<?> cls)
  	{
  		if(cls == null)
  			throw new NullPointerException("cls is null");
  		return appendResourcePathPrefixFor(sb, getPackageName(cls));
  	}
docs: Apend a package name converted to a resource path prefix.
  @param sb what to append to. If this is null, a new
  StringBuilder is created.
  @param cls The class to get the package name from.
  @return Path, starting and ending with a slash, for resources
  prefixed by the package name.
  @throws NullPointerException if cls is null.