Help needed understanding final keyword and use 3

Question

Hi Everyone,
I have been studying a book on multi-threading and have inadvertently come accross some code that I don't really understand. I am wondering if anybody can explain to me the following:
1). What effect does using the final keyword have when instantiating objects, and
2). How is it possible to instantiate an object from an interface?
public class BothInMethod extends Object
     private String objID;
     public BothInMethod(String objID)
          this.objID = objID;
     public void doStuff(int val)
          print("entering doStuff()");
          int num = val * 2 + objID.length();
          print("in doStuff() - local variable num=" + num);
          // slow things down to make observations
          try{
               Thread.sleep(2000);
          }catch(InterruptedException x){}
          print("leaving doStuff()");
     public void print(String msg)
          String threadName = Thread.currentThread().getName();
          System.out.println(threadName + ": " + msg);
     public static void main(String[] args)
          final BothInMethod bim = new BothInMethod("obj1");  //Use of final on objects?
          Runnable runA = new Runnable()      //Creating objects from an interface?
               public void run()
                    bim.doStuff(3);
          Thread threadA = new Thread(runA, "threadA");
          threadA.start();
          try{
               Thread.sleep(200);
          }catch(InterruptedException x){}
          Runnable runB = new Runnable()
               public void run()
                    bim.doStuff(7);
          Thread threadB = new Thread(runB, "threadB");
          threadB.start();
}If you know of any good tutorials that explain this (preferably URL's) then please let me know. Thanks heaps for your help.
Regards
Davo

Answer 1

final BothInMethod bim = new BothInMethod("obj1");  //Use of final on objects?
Runnable runA = new Runnable()      //Creating objects from an interface?          
     public void run()               
                                bim.doStuff(3);               
};Here final is the characteristics of bim reference variable and it is not the characteristics of class BothInMethod
This means u cannot use bim to point to some other object of the same class
i.e, u cannot do this
                   final BothInMethod bim = new BothInMethod("obj1"); 
                   bim  =  new   BothInMethod("obj2");  This bim is a constant reference variable which will point only to the object which it is initialized to
and not to any other object of the same class later on.
How is it possible to instantiate an object from an interface?Regarding this yes we cannot create an object from an interface but
but here it is not an interface u are providing the implementation of the interface Runnable
as
new Runnable()
}This now no longer stays an interface but now it is an object that implements the interface Runnable