Import new java classes into a running programm

Question

Hello, i have a small Java problem, i hope somebody knows an answer ...
I try to write a Java Programm, this programm starts and load a new class, this class is not defined inside the running programm, but the running programm should use the new class.
example:
// a class file in a directory somewhere at my harddisk
public void class X
void doSomething()
//Print "Hello world"
start programm A
Programm A does something, but doesn�t "know" class X, class X is not compiled with program A
after some seconds, A should load class X.
if (M == N) "import class X"
// At this moment, Programm A knows class X
X NewObjektX = new X();
NewObjektX.doSometing();
Thats my problem :)
I am sorry about my bad english, but its sadly not my first language.

Answer 1

Hello :)
Thx for an answer, i tried your solution, but i get another problem.
The type to create an object ist unknown.
i?ll post my exmaple code :
This class is not compiled with the main programm, only the class file is inside the directory of the main program.
public class SimpleClass
     int Information = 0;
     void printOnScreen()
         System.out.println("Varibale of the class:"
           + this.Information);   
This is the main programm:
public class Main {
     public static void main(String[] args)
          try
            Class newClass = Class.forName("SimpleClass");
            Object instance = newClass.newInstance(); 
              System.out.println(instance.getClass());
              // At this point no errors, the tpye of instance is
                 "SimpleClass"
              // This line occurs an error, the type "SimpleClass" is
              // unknown.
            SimpleClass newClassInstance = (SimpleClass) instance;
          catch (ClassNotFoundException e)
            System.out.println("Can?t open Class");
            System.err.println(e.getMessage());
          catch (InstantiationException e)
           System.out.println("Error1");
           System.err.println(e.getMessage());
          catch (IllegalAccessException e)
             System.out.println("Error2");
           System.err.println(e.getMessage());
      } // public static void main(String[] args)
} // public class MainI tried another solution with inheritance, i programmed a superclass, and choose the superclass as the type (the Superclass was compiled with the main programm).
The SimpleClass extends Superclass.
// works fine, but i dont want this type of solution :)
Superclass newClassInstance = (Superclass) instance;
How cann i solve the "unknown type" problem ?
SimpleClass newClassInstance = (SimpleClass) instance;