There are two ways to specify the parameter types. If you already have a reference to the Class, use that. For Android framework classes, you can often use something like String.class. If you don't have the class reference, you can simply use the full class name as a string, e.g. java.lang.String or com.example.MyClass. It will be passed to findClass with the same class loader that is used for the target method, see its documentation for the allowed notations.
