code: public boolean insertIntoTheCurrentSlot() {
  		if (!getVal(currentPos(), INTEGER).equals(EMPTY_CONST))
  			return false;
  		
  		setVal(currentPos(), INUSE_CONST);
  		return true;
  	}
docs: Marks the current slot as in-used.
  
  @return true, if it succeed. If the slot has been occupied, return false.