Fixed-width floating point number format

Question

In Java, I have the following code:

System.out.printf("%05.5f", myFloat);

This works well for any numbers which are less than 10, but for any number 10 or greater, the decimal places are trimmed to 5, but that doesn't compensate for the fact that the number before the decimal point is longer. I'd like to do one of the following:

12.3456
1.23456

(ie, the same number of digits), or:

12.34567
 2.34567

(ie, pad with spaces so that the decimal points and last digits line up).

I'd be happy if I could get either to work (both would be even better!).

Any thoughts? Thanks!

Answer 1

I figured out how to get it to do:

12.34567
 2.34567

Given a format string like "%x.yf", it will format with minimum width x, and post-decimal-point precision y. Since the pre-decimal point digits and the decimal point itself count towards the minimum width (x), the width has to be at least two larger than the precision. In particular, if a number is printed which is wider than the minimum width, it will not line up nicely with adjacent lines since those lines will be shorter. For example, if we try printing 10.1 and then 1.1 with a width of 3 and a precision of 1, we will get:

10.1
1.1

However, if we use a width of 4, 1.1 will be padded because it's not of the minimum width:

10.1
 1.1