Formatting numbers using DecimalFormat

Question

I am trying to format prices using DecimalFormat, but this isn't working for all variations.

DecimalFormat df = new DecimalFormat("0.##")
df.format(7.8)
df.format(85.0)

prints

7.80

and

85

but "7.79999" gets formatted as "7.8", not "7.80". I have tried doing things this way

DecimalFormat df = new DecimalFormat("0.00")

to force two dp, but then "85.0" gets formatted as "85.00" not "85"!

Is there a way of capturing all variations, so that prices are printed either as #, ##, or #.##? For example:

5, 55, 5.55, 5.50, 500, 500.40

Answer 1

There is a slight difference between these two formats. The "#.##" means it will print the number with maximum two decimal places whereas "#.00" means it will always display two decimal places and if the decimal places are less than two, it will replace them with zeros. see the example below with output.

public static final DecimalFormat df1 = new DecimalFormat( "#.##" );
public static final DecimalFormat df2 = new DecimalFormat( "#.00" );

System.out.println(df1.format(7.80));
System.out.println(df1.format(85));
System.out.println(df1.format(85.786));

System.out.println(df2.format(7.80));
System.out.println(df2.format(85));
System.out.println(df2.format(85.786));

And the output will be

7.8
85
85.79

7.80
85.00
85.79

Answer 2

This doesn't seem to be solved by a single formatter. I suggest you use "0.00" format and replace ".00" with an empty string.

public static String myFormat(double number) {
  DecimalFormat df = new DecimalFormat("0.00");
  return df.format(number).replaceAll("\\.00$", "");
}