abstract classes

[Andrew Lit]

where could i read about usage of abstract classes? i couldn't find nothing suitable for me on java.sun.com.
could you suggest me something?
thanx

[Cindy Glass]

If you do a google search on this site for +abstract+class you will find alot of reading material on the subject.

[Andrew Lit]

of course i will but i thought that someone could suggest something here
but thanx anyway

[Dan Chisholm]

The Java Language Specification has a good description of abstract classes and how to use them.
Java Language Specification section 8.1.1.1, Abstract Classes
[ July 24, 2002: Message edited by: Dan Chisholm ]

[Anthony Villanueva]

Basically, an abstract class is a class that cannot be instantiated. If you like, you can treat it as an interface. An abstract class is normally expected to be subclassed and its methods overriden/implemented by this subclass.
It doesn't matter if the abstract class has abstract methods or not. You can have an abstract with all of its methods implemented. However, a class that implements an interface or extends an abstract class, and does not implement all of superclass's methods, must be declared as an abstract class.

[Snigdha Solanki]

From the Java API, jav.io.InputStream is an abstract class.It is the superclass of all classes representing an input stream of bytes.
InputStream has the following abstract method:
public abstract int read();
which a subclass must provide an implementation for.Some of the subclasses of InputStream are FileInputStream,ByteArrayInputStream and FilterInputStream.

[Andrew Lit]

thank you very much