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javastringformatdouble

Java double to string with specific precision

I would like to convert double into String. I want it to have as few digits as possible and maximally 6.

So I found String.format("%.6f", d) which converts my 100.0 into 100.000000. Max precision works correctly, but I would like it to be converted to 100 (minimum precision). Have you got any idea what method is working like that?

Solution

  • Use DecimalFormat: new DecimalFormat("#.0#####").format(d).

    This will produce numbers with 1 to 6 decimal digits.

    Since DecimalFormat will use the symbols of the default locale, you might want to provide which symbols to use:

    //Format using english symbols, e.g. 100.0 instead of 100,0
new DecimalFormat("#.0#####", DecimalFormatSymbols.getInstance( Locale.ENGLISH )).format(d)

    In order to format 100.0 to 100, use the format string #.######.

    Note that DecimalFormat will round by default, e.g. if you pass in 0.9999999 you'll get the output 1. If you want to get 0.999999 instead, provide a different rounding mode:

    DecimalFormat formatter = new DecimalFormat("#.######", DecimalFormatSymbols.getInstance( Locale.ENGLISH ));
formatter.setRoundingMode( RoundingMode.DOWN );
String s = formatter.format(d);