ISay obj=(ISay)Class.forName(args[0]).newInstance(); obj.say();

class mainClass  

 { 

public static void main(String[] args)  

{ 

System.out.println(args[0]); 

try{ 

         ISay obj=(ISay)Class.forName(args[0]).newInstance(); 

obj.say(); 

} 

catch (InstantiationException e) { 

// TODO Auto-generated catch block 

e.printStackTrace(); 

} catch (IllegalAccessException e) { 

// TODO Auto-generated catch block 

e.printStackTrace(); 

} catch (ClassNotFoundException e) { 

// TODO Auto-generated catch block 

e.printStackTrace(); 

} 

} 
}

public interface ISay
 {
void say();
 }  
class SayHello implements ISay 
 {
public void say() 
{
System.out.println("Hello!");
}
 }
class SayBye implements ISay 
 {
public void say() 
{
System.out.println("Bye!");
}
 }