private boolean isJump(int r, int c, int tr, int tc) {
		if (sourceNotEmpty(r, c) && targetEmpty(tr, tc)) {
			
			Move move = Move.instance(r, c, tr, tc, this);
			if (move.isJump()) {
				int[] j = move.getJumpedPosition();
				
				CheckerType type = getCell(r, c);
				if (isOponent(type, j[0], j[1])) {
					return true;
				}
			}
		}
		return false;
	}