RE: Understanding Implements

[Joe Teff <joeteff@xxxxxxxxxxxxx>]

The following is an interface, stored in a .java source file and compiled the 
same as classes:

public interface Noisable {
   public void makeSound();
}

Notice that the method only contains the signature and no implementation. 
Methods in an interface are abstract. The interface only requires that you 
supply the method(s) listed. There is no inheritence here.

This class will implement that interface:

public class Airplane implements Noisable {
   // various methods and data
   public void makeSound() {
      // code to here to make airplane noise
   }
}

This class will not compile unless I code all methods listed in the interface, 
hence the "contract" reference.

Now lets make an application that generates sounds:

public class GenerateSounds {
   public static void blareItOut( Noiseable obj ) {
      obj.makeSound();
   }
}

I can call GenerateSounds.blareItOut(xxx) where xxx is an object created from 
any class that implements Noisable. The actual code to make the noise is coded 
into each class's makeSound() method, thus each one will do it slightly 
different. blareItOut() doesn't care how the code works, it just cares that the 
appropriate method is there. It doesn't even care what kind of object (class) 
it even is. The only thing it knows is that it has to have a makeSound() method 
that it can call.

Joe Teff

------Original Message------
From: "Eyers, Daniel" <daniel.eyers@honeywell.com>
To: "'JAVA400-L@midrange.com'" <JAVA400-L@midrange.com>
Sent: March 21, 2001 2:30:49 PM GMT
Subject: RE: Understanding Implements


From your post, I would guess SingleThreadModel is a marker.  

From the various posts, I gather that Interfaces are containers that store
classes that have that are similar funtionality but diverse ways of
implementing functionality.

I still a bit hazy on your statement "if you implement the required
methods."  Can you elaborate a bit....

thanks!

dan


-----Original Message-----
From: Joe Teff [mailto:joeteff@earthlink.net]
Sent: Tuesday, March 20, 2001 1:02 PM
To: JAVA400-L@midrange.com
Subject: RE: Understanding Implements


Interfaces are used in two ways:
1. Contracts - if you implement the required methods, then you can be one
(i.e. your object can be referenced by that kind of data type).  Container c
= new JPanel();
2. Markers - no methods to implement. Used to mark objects for a specific
purpose. Serializable is an example. It has no methods. Any class that
implements it, can be used in readObject() and writeObject() methods.
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