public void calculate(float num)
    {
	switch(oper)
	    {
	    case "+":
		total += num;
		break;
	    case "-":
		total -= num;
		break;
	    case "*":
		total *= num;
		break;
	    case "/":
		total /= num;
		break;
	    case " ":
		total = num;
	    case "=":
	    default:
	    }


    }