PACKAGE

[thomas davis]

Hi All,
Given below are the steps followed:
1) I have one class that is stored in a directory structure given below:
D:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\com\sharedapps\globalrfx\beans\service\modify\ChangeDB.class
2) I set class path like this: D:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\;
3) And I put my first statement in that class as given below
package com.sharedapps.globalrfx.beans.service.modify;
It compiled fine
4) I have got another class up in the hierarchy as given below:
D:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\com\sharedapps\globalrfx\beans\common\Contact.class

6) This also compiled fine
7) And What I did is I append classpath as given below
D:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\com\sharedapps\globalrfx\beans\service\modify\;
8) And I removed package declaration from top of class ChangeDB,It again compiled fine.(removed package com.sharedapps.globalrfx.beans.service.modify;
)
9) But When I try instantiate ChangeDB in Contact class and I imported all classes from modify where class ChangeDB LOCATED. import com.sharedapps.globalrfx.beans.service.modify.*; I got error as given below
Contact.java:24: cannot access com.sharedapps.globalrfx.beans.service.modify.ChangeRemoveATMDB
bad class file: J:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\com\sharedapps\globalrfx\beans\service\modify\ChangeDB.class
class file contains wrong class: ChangeDB
Please remove or make sure it appears in the correct subdirectory of the classpath.
ChangeRemoveATMDB objDB = new ChangeRemoveATMDB();
Even though I imported the class, why I am getting above said error? I set the classpath till where the class is situated. Now JVM can see where the class is located and that can be accessed from that package also.
But When I added the package statement again in ChangeDB.class,
It compiled fine!!! I was able to access the same class from the class Contact in other folder D:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\com\sharedapps\globalrfx\beans\common\
How does JVM locate the classes and how does it load the class?
Why package declaration is necessary even if I set classpath till that point where class is resided? Can anybody explain about the relationship between classpath, package declaration et all?

[Dhamodharan Krishnan]

Hi Thomas,

 
1) I have one class that is stored in a directory structure given below:
D:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\com\sharedapps\globalrfx\beans\service\modify\ChangeDB.class
2) I set class path like this: D:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\;
3) And I put my first statement in that class as given below
package com.sharedapps.globalrfx.beans.service.modify;
It compiled fine
4) I have got another class up in the hierarchy as given below:
D:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\com\sharedapps\globalrfx\beans\common\Contact.class

6) This also compiled fine
7) And What I did is I append classpath as given below
D:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\com\sharedapps\globalrfx\beans\service\modify\;
8) And I removed package declaration from top of class ChangeDB,It again compiled fine.(removed package com.sharedapps.globalrfx.beans.service.modify;
)
[B]<Dhamo>
I think you have compiled only ChangeDB after removing its package name. 
Did you compile com.sharedapps.globalrfx.beans.service.modify.ChangeRemoveATMDB after that.
<Solution>
i.e. Remove package structure in ChangeDB.
Put it wherever you want and you know very well to set the classpath till that directory.
Fine. But did you import this class explicitly in com.sharedapps.globalrfx.beans.service.modify.ChangeRemoveATMDB
You have to use the following statement 
<Stmt>import ChangeDB; </Stmt>
</Solution>
<Inference>
Package is just a home for a class. Till you put a class in a directory and mention it as its package, then you refer with the package. It is enough if you include that home in the import statement.
He belongs to Plot #14.
The people in Plot #14 refer to all the people in that house.
Imagine if you refer to people in a street.
A man belongs to FirstCrossStreet.Plot#14
A person by name HomelessCOP i.e Homeless Care of Platform is there standing in Plot#14's garden.
He doesnt have a house of his own. So to refer to him you say HomelessCOP standing in Plot#14's garden. i.e. you set the claspath till Plot#14.
Hope this explains you.
</Inference>
Make a try and let me know.a
</Dhamo>[/B]
9) But When I try instantiate ChangeDB in Contact class and I imported all classes from modify where class ChangeDB LOCATED. import com.sharedapps.globalrfx.beans.service.modify.*; I got error as given below
Contact.java:24: cannot access com.sharedapps.globalrfx.beans.service.modify.ChangeRemoveATMDB
bad class file: J:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\com\sharedapps\globalrfx\beans\service\modify\ChangeDB.class
class file contains wrong class: ChangeDB
Please remove or make sure it appears in the correct subdirectory of the classpath.
ChangeRemoveATMDB objDB = new ChangeRemoveATMDB();
Even though I imported the class, why I am getting above said error? I set the classpath till where the class is situated. Now JVM can see where the class is located and that can be accessed from that package also.
But When I added the package statement again in ChangeDB.class, 
It compiled fine!!!! I was able to access the same class from the class Contact in other folder D:\WebSphere\AppServer\installedApps\globalrfx.ear\global.war\WEB-INF\classes\com\sharedapps\globalrfx\beans\common\
How does JVM locate the classes and how does it load the class?
Why package declaration is necessary even if I set classpath till that point where class is resided? Can anybody explain about the relationship between classpath, package declaration et all?