Invoke a Class from a Particular JAR file

[Neelakantan Kuthalanathan]

I have a Class with under a package com.pkg.test which I have a Packaged as JAR file
say JAR1

----------------------JAR1-------------------------------------

package com.pkg.test;
 
public class ClassA {
 
public static int T = 1000;

private String id = null;

public ClassA(){
this.id = "In Jar 1";
}

public void printID(){
System.out.println(this.id);
}

}

--------------------------------------------------------------------

I have another JAR file with the same class name but differnt implemetaion and value of static variable
under same Package structure...Say

-------------------------JAR2---------------------------------------

package com.pkg.test;
 
public class ClassA {
 
public static int T = 555;

private String id = null;

public ClassA(){
this.id = "In Jar 2";
}

public void printID(){
System.out.println(this.id);
}

}

---------------------------------------------------------------------------

Simalarly I have another JAR file with the same class under same Package structure...Say

-------------------------JAR3---------------------------------------

package com.pkg.test;
 
public class ClassA {
 
public static int T = 222;

private String id = null;

public ClassA(){
this.id = "In Jar 3";
}

public void printID(){
System.out.println(this.id);
}

}

---------------------------------------------------------------------------




Now I create Another MainClass and import all these three JAR files into my class-path
(I included the JAR files in this order : JAR1,JAR2,JAR3)

--------------------------------------------------------------------------------------------

package com.dynamicClass.test.main;
 
import com.pkg.test.ClassA;
 

 
public class JARTestMainClass {
 
/**
 * @param args
 */
public static void main(String[] args) {
System.out.println("Executing the project JARTest");
System.out.println("Getting the Static variable T from ClassA");
System.out.println("Value of T="+ClassA.T);
System.out.println("Calling printID method from  ClassA");
(new ClassA()).printID();
}
 

 
}

>>>>>>>>>>>>>>>>>>I get the following output>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Executing the project JARTest
Getting the Static variable T from ClassA
Value of T=1000
Calling printID method from ClassA
In Jar 1
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

If I include the JAR file in the following order :JAR3,JAR1,JAR2 ; then i get following output

Executing the project JARTest
Getting the Static variable T from ClassA
Value of T=222
Calling printID method from ClassA
In Jar 3


-------------------------------------------------------------------------------------------------

My question is how can we control this behaviour ,I mean how can we say to JAVA to use the ClassA
from the particular JAR file at runtime.My requiremnt is I need to access the methods of ClassA from
JAR1,JAR2 and JAR3.

Any Idea regarding this.

Thanks
Neel

[Ilja Preuss]

Instead of putting the jars onto the classpath, you'll need to use your own classloader(s).

Can you tell us more about where that requirement is coming from?