How to restrict the decimal place of a floating point number?

Question

Hi,
Here is my code:
public void TwoDecimal(double u){
     String w = Double.toString(u);
     int c = w.length();
     System.out.println(c);
     if (c <= 5)
        double a = Double.parseDouble(w);
        System.out.println(a);
     else
        System.out.println("Invalid input!");
  }I want to show a floating point number which has 2 digits and 2 decimal places, e.g. 45.82, 29.67. This number is input by user and passed as a parameter.
For those case like the above sample floating point numbers, it can display the proper value of 'c'. e.g. 45.67 will display 5.
However, when I passed 99999, it will show 7; 9999 will return 6, not 5.
So, if the user does not input the '.', does it append 2 implicit chars to it? i.e. 99999.0 and 9999.0. So, that's why it returned 7 and 6 for the length of the string respectively.
How can I fix it?
and
Does it has better algorithm?
Pls advise.
gogo

Answer 1

When dealing with a known precision, in your case hundredths, it is often a good idea to use an integer type and add in the decimals on printing only. This is often the case in banking systems. Almost all of them use integer types, (read long) in pennies to store monitary values. Ever seen someone type in a value for a credit card machine? For something like $20 they press.. "2" "0" "0" "0" The machine knows the lowest denomonation in a cent, so it knows where to put the decimal place. I suggest you do something like this. It also helps to avoid base 2 round off errors.
-Spinoza