public Checker getChecker(int x, int y)
      {
         for(Checker checker: redCheckers)
         {
            if( (checker.checkX(x)) && (checker.checkY(y)) )
            { 
               return checker;
            }
          
            
         }
         for(Checker checker: blackCheckers)
         {
            if( (checker.checkX(x)) && (checker.checkY(y)) )
            { 
               return checker;
            }	 
          
         }
         return null;
      	
      }