public interface Comparable
{
// Compares the executing object to the parameter
// returns relative ordering as integer <0, =0, or >0
public int compareTo(Object o);
}
public interface Iterator
{
// return true if executing object has one or more objects
// that have not been returned by next method yet.
public boolean hasNext();
// return a reference to the next object in the iterator
public Object next();
//remove item most recently returned by next method from the collection
public void remove();
}
class Talking
{
// reference into a class reference to invoke its unique method.
public static void main (String[] args)
{
// declare an interface reference
Speaker current;
// instantiates a Dog object using the interface reference
current = new Dog();
// invokes one of the common methods
current.speak();
// instantiates a philosopher object using the interface reference
current = new Philosopher ("I think, therefore I am."); //---> line (*)
// invokes the common method
current.speak();
// casts the interface to make the Speaker a Philosopher
((Philosopher) current).pontificate();
}
}
Note that we cannot just use th dot operator between current and this method, because current is of type Speaker not Philosopher while this method is a member of Philosopher class. Remember, every Philosopher is a Speaker, but not every Speaker is Philosopher. The line (*) makes current a philosopher Speaker, but not a complete Philosopher whcih can invoke any method in Philosopher class. That why the casting is needed.