Why do I get “object is not an instance of declaring class” when invoking a method using reflection?

Question

public class Shared {

    public static void main(String arg[]) throws SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, I         


        

Answer 1

When you invoke a method via reflection, you need to pass the object you are calling the method on as the first parameter to Method#invoke.

// equivalent to s1.testParam("", obj)
testParamMethod.invoke(s1, "", obj);

Answer 2

 testParamMethod.invoke("", obj); ///// here getting error

The first parameter to invoke must be the object to invoke it on:

 testParamMethod.invoke(s1, "", obj);