格式化浮点数

Question

I have a variable of type double , I need to print it in upto 3 decimals of precision but it shouldn't have any trailing zeros...

eg. I need

2.5 // not 2.500
2   // not 2.000
1.375 // exactly till 3 decimals
2.12  // not 2.120

I tried using DecimalFormatter , Am i doing it wrong?

DecimalFormat myFormatter = new DecimalFormat("0.000");
myFormatter.setDecimalSeparatorAlwaysShown(false);

Thanks. :)

Answer 1

Try the pattern "0.###" instead of "0.000" :

import java.text.DecimalFormat;

public class Main {
    public static void main(String[] args) {
        DecimalFormat df = new DecimalFormat("0.###");
        double[] tests = {2.50, 2.0, 1.3751212, 2.1200};
        for(double d : tests) {
            System.out.println(df.format(d));
        }
    }
}

output:

2.5
2
1.375
2.12

Answer 2

Your solution is almost correct, but you should replace zeros '0' in decimal format pattern by hashes "#".

So it should look like this:

DecimalFormat myFormatter = new DecimalFormat("#.###");

And that line is not necesary (as decimalSeparatorAlwaysShown is false by default):

myFormatter.setDecimalSeparatorAlwaysShown(false);

Here is short summary from javadocs:

Symbol  Location    Localized?  Meaning
0   Number  Yes Digit
#   Number  Yes Digit, zero shows as absent

And the link to javadoc: DecimalFormat

Answer 3

Use NumberFormat class.

Example:

  double d = 2.5; NumberFormat n = NumberFormat.getInstance(); n.setMaximumFractionDigits(3); System.out.println(n.format(d)); 

Output will be 2.5, not 2.500.