Inheritance and Interface invocation Query

Question

interface IProduct{
     void getProductName();            
abstract class Option implements Product{
             void exercisePrice();
             void premiumPaid();
class Option1 extends Option{
           // Implement all abstract methods defined in Option and IProduct.
class Option2 extends Option{
     // Implement all abstract methods defined in Option and IProduct.
class Trade{
           public Trade(IProduct p){
     p.getProductName()   // I can only get this method behaviour.
                // My Query
                // I also need to invoke the methods exercisePrice() and premiumPaid() defined in Option1 and Option2
                // If I use instanceof,the code will get cluttered and ugly.
                                 if p instanceof Option1
                                 Option1 op1 = ((Option1) p);
                                 op1.exercisePrice();
                                  if p instanceof Option2
                                  if p instanceof OptionN
class TestHarness{
         public static void main(String args[]){
         // Create an option
         Option1 option1 = new Option1();
         // Trade in the product
         Trade trade = new Trade(option1);
         Query:
         The Trade constructor defines IProduct.
         IProduct can be a concrete Bond,Option,CDS,IRS etc.
         How do I get the methods defined in subclasses Option1 and Option2 or for any concrete subclass of IProduct?
         Is there a way of dynamically invoking the methods of the object created?
        Or do I need to change the design.
}

Answer 1

It looks to me like you're violating the Liskov Substitution Principle.
"The LSP says that the users of base classes should not have to do anything special in order to use derivatives."
- R. MartinThis also violates the Open/Closed principle, because whenever you add a new Option concrete class, you're going to have to update your Trade class (it's not "closed to modification" when the environment around it changes).
The "fix" is just that its not a good idea to force the polymorphism by using instanceof. You should either:
1. Get rid of the IProduct interface completely and treat each product type separately.
2. Reconsider your base class (in this case, IProduct) to see if it really can contain additional behavior applicable to all products.
The previous post about the visitor pattern is interesting, but I don't see how it applies to this example (perhaps some more light could be shed there by the poster).