public String multiply(String num1, String num2) {
    	if (num1.equals("0") || num2.equals("0"))
    		return "0";
    	String tb[] = new String[10];
    	tb[0] = "0";
    	for (int i = 1; i < 10; i++)
    		tb[i] = add(tb[i-1], num1);
    	
    	int len = num2.length();
    	String sum = "0";
    	String div = "";
    	for (int i = len - 1; i >= 0; i--)
    	{
    		String mul = tb[num2.charAt(i) - '0'] + div;
    		sum = add(sum, mul);
    		div += "0";
    	}
    	return sum;
    }