final void lock(){
  if (compareAndSetState(0,1))   setExclusiveOwnerThread(Thread.currentThread());
 else   acquire(1);
}

final void lock ( ) { if ( compareAndSetState ( 0 , 1 ) ) setExclusiveOwnerThread ( Thread . currentThread ( ) ) ; else acquire ( 1 ) ; }
performs lock . try immediate barge , backing up to normal acquire on failure .
