如何摆脱小数点前小于零的小数点前的零？

Question

I am doing a rather large project (for me, is an AP JAVA course in high school). Anyways, for a portion of the project I need to be able to round a decimal and output it without the zero at the beginning before the decimal.

Ex: .4999 rounds ---> 0.5 I need: .4999 round ---> .5

Thanks in advance

Answer 1

As Ingo mentioned, you'll need to get a String representation of the number in order to modify the output as desired. One solution would be to use java.text.NumberFormat . setMinimumIntegerDigits(0) seems to fit the bill. I'm sure there are plenty more options as well.

Answer 2

Try this:

public static String format(double value, int decimalPlaces) {
   if (value >= 1 || value < 0) {
      throw new IllegalArgumentException("Value must be between 0 and 1");
   }
   final String tmp = String.format("%." + decimalPlaces + "f", value);
   return tmp.substring(tmp.indexOf('.'));
}

Examples:

System.out.println(format(0.4999d, 1)); // .5
System.out.println(format(0.0299d, 2)); // .03
System.out.println(format(0.34943d, 3)); // .349

Working Fiddle

Answer 3

The DecimalFormat class can be used.

DecimalFormat df = new DecimalFormat("####0.0");
System.out.println("Value: " + df.format(value));

Answer 4

May seem weird to you, but you can use regex to strip off the leading zero like this:

(assuming that you already know how to round the decimal place to one)

        double value = 0.5;

        String val = Double.toString( value ).replaceAll( "^0(\\..*)$", "$1" );

        System.out.println( val );

Console:

       .5