Wat are adapter classes ?

[Saurabh Agrawal]

Hi ,

Can anyone make it clear the term adapter classes in context of java??

Hoping to hear from neone soon,
Saurabh

[Maulin Vasavada]

Hi Saurabh
Usually we use adapter classes when we have interfaces having many methods in there but we just need to override every method while using it. e.g.
WindowListener has many methods but if in our application we need only closingWindow() to implement what we have to do? Java enforces that we implement ALL methods in window listener interface. So, what we will end up
doing is- "write empty method implementation for those which don't care about". Now, this can become quite annoying if we have many such interfaces to
deal with, right? So, Java provides some inbuilt classes. e.g. WindowAdapter that implements all methods in WindowListener as empty implementation. Now, we can just say "extends WindowAdapter" and override just one method in our implementation.
This is the most specific use of Adapter classes I guess w.r.t. to AWT,Swing and all...
hth
maulin

[Ilja Preuss]

Notice that this is quite different from the Adapter design pattern!
In the adapter design pattern, you adapt the interface of a class/object, to the interface a client needs. For example, say you have a method which expects an Iterator as argument, but you only have an Enumeration. Than you could write an Adapter implementing the Iterator interface by delegating to the Enumeration.