Runnable to Thread Casting

[Balaji Bang]

 public class AnoThreads{

     static volatile java.io.PrintStream s=System.out;

     public static void main(String args[]){

          Runnable r1=new Runnable(){
               public void run(){
                    synchronized(s){
                         System.out.print("SCJP-1 ");
                         System.out.print("SCJP-2 ");
                         System.out.print("SCJP-3 ");
                    }
               }
          };

          Runnable r2=new Runnable(){
               public void run(){
                    synchronized(s){
                         System.out.print("SCEA-1 ");
                         System.out.print("SCEA-2 ");
                         System.out.print("SCEA-3 ");
                    }
               }
          };
//r1.run();
//r2.run();
//Thread t1=new Thread(r1);
//Thread t2=new Thread(r2);
          Thread t1=(Thread)r1; //ClassCastException
         Thread t2=(Thread)r2;//ClassCastException
          t1.start();
          t2.start();

     }

}   

Why the casting gives ClassCastException? Thread class provides the implementation for Runnable interface. Then why cannot we cast???

[Abhi vijay]

This is because r1 is an implementer of the Runnable Interface. Thread class also is an implementer of Runnable. But there is no relation between r1(anonymous sub-class referenced by r1) and the Thread class.

[Balaji Bang]

ohhhhhh. Yes r1 is just an implementor reference not Runnable reference. So we cannot . Thank you