Running Two Classes with same name in single VM

Hi!

The Classes are of the same name but their location in different directories indicate a difference in package names. If they don't have a package specification, you can do so by a package statement at the beginning of each file.

So, you can always load them in the same VM as:
Class.forName("com.ibm.Class1");
Class.forName("com.microsoft.Class1");

Hope it helps!

sghosh

the JVM loads the class it find first in the class path.
so, having two classes with the same name on diferent entries in the classpath is a bad idea.

just make sure that there is only one class with that name in the classpath when you run the program.
you can change the classpath before running it every time.

Hi omry_y,

just wanted to have a discussion.

why are u saying it as a bad idea. We can see such demonstration in jdk api itself. that is what is called as namespaces.

take for example java.util.Date and java.sql.Date classes.

it makes good sense to name the class with what it is modelled for.

As far as we are referring the class name with fully qualified package name prefixes, i do not see any problem.
Bcos the jvm will load the correct class.

Any comments ?.

vraghav

we dont understand the question in the same way.

ofcourse having two classes with the same name in diferent packages is fine.
but having two classes in the same package in diferent entries of the classpath, it not fine.
suppose your classpath looks like
c:\jdk1.2.2\lib\;c:\yourprog1;c:\yourprog2
and you have a class named blah.Blah in
c:\yourprog1
and
c:\yourprog2

thats not good.

Hi omry_y,

i got ur point. I understand now.

Thanks

vraghav

Hi All,
Thanks for your responses, but still I am in a fix.
The actual problem is I have to run the two versions of the same application in the same JVM so the classes and packages names are the same only the toplevel directories are different
e.g one version is in jdk1.2\com\sun\swing where com.sun.swing is the package name and jdk1.2 is the classpath specified
and other version is jdk1.3\com\sun\swing where com.sun.swing is the package name and jdk1.3 is the classpath specified

now how should I go with this problem, omry I know this is a bad idea, but I got to find a solution for this.

regards
Mak

makrand,

Having different versions of the same class in your classpath is not a problem (and very useful in variour scenarios), your problem is that the classloader will only load the first version it finds.
Without using your own classloader I'm not sure if you can load different versions of the same class.
Why do you need to run the two in the same JVM?  Why not run app twice with different classpaths?

Hey!

You can specify a CLASSPATH while you are running the application. Say,

java -classpath c:\jdk1.2\com\sun\swing;<Other common directories> MyApplication

OR

java -classpath c:\jdk1.3\com\sun\swing MyApplication

Hope it helps!
sghosh

Hi,
I need to run the two versions of the same appln, in the same JVM as these two versions r going to communicate with each other to get some results.
so if I got to write a classloader, how will that help me out.

regards
Mak

why exactly do you need to do such a thing?
it seems like you are going in the wrong direction, whatever it is you are trying to do.

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- Split points between objects and vraghav

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