class names with "$"..

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Frances Del Rio - 14 Jun 2005 19:04 GMT

why do some classes have "$" in the names? I have never seen this
before... I just compiled some code I dl'd and form some source code
files I get three diff. classes with dollar signs... for example for a
source code file called 'Connect.java' I get these three classes...

Connect$1.class
Connect$2.class
Connect$3.class

thank you.... Frances

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TechBookReport - 14 Jun 2005 19:55 GMT

> why do some classes have "$" in the names? I have never seen this
> before... I just compiled some code I dl'd and form some source code
[quoted text clipped - 6 lines]
>
> thank you.... Frances

Your class contains anonymous inner classes, each of these compiles to its
own class file (numbered sequentially).

HTH
====================================================
TechBookReport Java http://www.techbookreport.com/JavaIndex.html

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Frances Del Rio - 14 Jun 2005 20:26 GMT

>>why do some classes have "$" in the names? I have never seen this
>>before... I just compiled some code I dl'd and form some source code
[quoted text clipped - 9 lines]
> Your class contains anonymous inner classes, each of these compiles to its
> own class file (numbered sequentially).

ok, still need to learn about inner classes, but thank you for your
response.....

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Leon - 14 Jun 2005 22:00 GMT

[...]

> ok, still need to learn about inner classes, but thank you for your
> response.....

[...]

An inner class is a class within a class:

Class OuterClass {

// Attributes and methodes

Class InnerClass {

// Attributes and methodes

}
}

Greetings, Leon.

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Frances Del Rio - 14 Jun 2005 22:34 GMT

> [...]
>
[quoted text clipped - 15 lines]
> }
> }

thank you Leon.. so every time you have nested classes, when you
compile, the nested class becomes a class of its own? this happens
every time you nest one class inside another? (except in a servlet, I
suppose (which of course is techn. a class......;).. I mean classes
inside a servlet are not techn. inner classes, right?)

(so here yr inner class has a diff. name from main class.. in my ex.
(taken from a real package w/a whole lot of classes) this comes from a
source code file called Connect.java, ran a search for word "class" in
it, I don't see any nested classes (no inner classes called "Connect" at
any rate..) thanks again, Leon... Frances

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Andrew McDonagh - 14 Jun 2005 23:12 GMT

>> [...]
>>
[quoted text clipped - 27 lines]
> it, I don't see any nested classes (no inner classes called "Connect" at
> any rate..) thanks again, Leon... Frances

Leon's example is unfortunate that it described 'named' inner classes.
When compiled you should see the likes of

Outer$NamedInner.class

Whereas what you are seeing :

Connect$1.class
Connect$2.class
Connect$3.class

is the binary class files for 'anonymous' inner classes.

e.g.

public void someMethod() {

////////////////// This is the anonymous class...

Runnable r = new Runnable() {

public void run() {
System.out.printLn("do something when called");
}
};

////////////

r.run();

}

Runnable is an standard Java Interface, but anonymous classes can also
be derived from normal classes too in the same way as above.

Andrew
}

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Leon - 15 Jun 2005 00:03 GMT

[...]

>>> An inner class is a class within a class:
>>>
[quoted text clipped - 8 lines]
>>> }
>>> }

[...]

> Leon's example is unfortunate that it described 'named' inner classes. When
> compiled you should see the likes of
[quoted text clipped - 23 lines]
>
> ////////////

[...]

Understood. Thanks for explaining..

Greetings, Leon

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Juha Laiho - 17 Jun 2005 21:20 GMT

Frances Del Rio <fdr58@yahoo.com> said:

>> An inner class is a class within a class:
>>
[quoted text clipped - 14 lines]
>suppose (which of course is techn. a class......;).. I mean classes
>inside a servlet are not techn. inner classes, right?)

It's not often when you see inner classes in a servlet. Note the
construct above; there's the top-level class declaration (class OuterClass),
and completely nested within it another (class InnerClass).

When you write a servlet, you pretty much have

public class MyServlet extends HttpServlet {
// ... variables and methods for MyServlet
}

Of course, there's no restriction why you couldn't have inner classes
within servlets, but I think that'd rather often indicate that there's
too much processing logic in the servlet (instead of decoupling the
logic to a set of generic classes, and only using servlets to create
a web interface for the logic).

Signature

Wolf a.k.a. Juha Laiho Espoo, Finland
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Tor Iver Wilhelmsen - 18 Jun 2005 12:51 GMT

> public class MyServlet extends HttpServlet {
> // ... variables and methods for MyServlet
> }

Well, usually just methods. Putting state in a servlet - especially
state related to requests - is evil. State belongs in request, session
or application scope explicit, not in any servlet class variables.

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class names with "$"..

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