Cast Class to some interface

Question

Suppose, i have an
Object obj;
then i can cast it to any interface an� invoke any instance methods/
but if i have
Class myClass = obj.getClass()...
and i now in advance that this class implements some static method of some interface
how can i cast a Class instance?
something like that
((MyInterface)myClass).some_static_method
???

Answer 1

well, how can i directly invoke static method,
if i use dynamic loading??Dynamic loading is not a good mechanism for bringing in static methods. If the loaded classes are yours and you can still change the design, the "canonical" way would be to make the method non-static and provide a default instance (or even a singleton) in a static variable (presumably in the base class that is not loaded dynamically) that gets initialized when loading the subclass. This works fine if your program uses that one subclass throughout its lifetime and the only reason to load it dynamically was that the reference to the class should not be hardcoded.
If you have several subclasses at the same time, then your problem would be how to know when to call this subclass and when that one. Once you know that, you will also have a way to know which instance to call - assuming that you create an instance of each subclass as it is loaded to provide the non-static method. Maybe you would provide the instances in a HashMap or whatever...
If you use reflection you can also call a static method in a non-hardcoded way. This is more cumbersome to code and perhaps slower in speed. Since you have no instance, you will need to query the class by name (unless you have direct access to the loaded java.lang.Class), i.e. you will have to know its fully qualified classname.
Class myClass = myClassLoader.loadClass("some_class");
then, i know, that this class extends abstract class
with some static methods
and now, i want something like this
((MyAbstractClass)myClass).method1();
of course, i could do the following
Object obj = myClass.newInstance();only if it has a default constructor!
((MyAbstractClass)obj).method1()But this is the same as:
MyAbstractClass.method1();
I.e. you would call the static method in MyAbstractClass, NOT in a (perhaps dynamically loaded) subclass!
This is true because for static methods no dynamic (i.e. runtime) binding takes place.
In other words: There is no true polymorphism for static methods. For polymorphism with dynamic binding you need objects. For static methods you need no objects and never should create objects for invocation because that is not only unnecessary but suggests dynamic binding would occur - which is a wrong suggest.
but i don't want to do so, because i use static methods
only and thus do not need an object to create !!!
is there a method to do soOnly when you know the classname or the java.lang.Class somehow and are using reflection as described in more detail in an earlier message in this thread. Otherwise - i.e. if you need true polymorphism with dynamic binding - you would have to use non-static methods and provide some objects to call the method on them.