Doing strict MVC checks that View and Control components of a Model truly are valid Viewers for updates, and Controlers for state changes within Java.

StrictJavaMVCChecking.java

/* public interfaces for controller and view components to implement for a model */
public interface StrictModelViewer extends Observer {};
public interface StrictModelComtroller;

public class StrictModel extends Observable {

  /* All model changing calls must come from classes implementing StrictModelController */
  public void alterModelState() {
    assert ReflectionUtilities.callerImplements(StrictModelController.class);
    this.setChagned();
    this.notifyObservers();
  }

   /* Only implementers of StrictModelViewere can become observers */ 
   public void addObserver(Observer observer) {
     assert (ReflectionUtilities.classImplements(observer.getClass(), StrictModelViewer.class)) : 
      "observer specified does not implement the interface StrictModelViewer";
     super.addObserver(observer);
  }
}

final class ReflectionUtilities {
  
  /**
   * Checks to see if the method calling whatever method that invokes
   * <tt>callerImplements</tt> implements the supplied interface.
   * @param theInterface
   * @return
   */
  public static boolean callerImplements(Class<?> theInterface) {
    
    StackTraceElement[] elements = new Throwable().getStackTrace(); 

    String callerClassName = elements[2].getClassName(); 
    Class<?> callerClass = null;
    try {
      callerClass = Class.forName(callerClassName);
    } catch (Exception e) {
       return false;  
    }
    return classImplements(callerClass, theInterface);
  }
  
  /**
   * Checks to see if the supplied class implements the supplied interface.
   * @param theClass
   * @param theInterface
   * @return
   */
  public static boolean classImplements(Class<?> theClass, Class<?> theInterface) {
    Class[] interfaceArray = theClass.getInterfaces();
    for (Class<?> thisInterface : interfaceArray) {
      if (thisInterface.equals(theInterface)) {
        return true;
      }
    }
    return false;
  }
}