NumberFormat setMaximumFractionDigits method

Question

I am trying out the methods and the functionality of the class NumberFormat and I have reached to a strange result. I compile and run the following program:

public static void main(String[] args) {

Locale loc = Locale.US;
    NumberFormat nf = NumberFormat.getInstance(loc);
    System.out.println("Max: "+nf.getMaximumFractionDigits());
    System.out.println("Min: "+nf.getMinimumFractionDigits());
    try {
        Number d = nf.parse("4527.9997539");
        System.out.println(d);
        // nf.setMaximumFractionDigits(4);
        System.out.println(nf.format(4527.999753));
    } catch (ParseException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}

The output is:

Max: 3
Min: 0
4527.9997539
4,528

That means that it does not take into account any fraction digit. If I uncomment the line:

nf.setMaximumFractionDigits(4);

the output is:

Max: 3
Min: 0
4527.9997539
4,527.9998

In other words it works OK. What is actually happening with method setMaximumFractionDigits() and it does not bring the number containing 3 fraction digits in the first case?

Answer 1

I found the answer finally. The method setMaximumFractionDigits() has an effect only on the method format(). It has nothing to do with parse(). In my code fragment I use the method format() after setting manually the number of fraction digits to 4, consequently it affects the result.

Answer 2

If you want to set manually the number of decimal places use one of the following options:

Firstly:

  //sets 'd' to 3 decimal places & then assigns it to 'formattedNum'
   String formattedNum = String.format("%.3f", d); //variable 'd' taken from your code above 

OR

  //declares an object of 'DecimalFormat'
   DecimalFormat aDF = new DecimalFormat("#.000"); 

  //formats value stored in 'd' to three decimal places
   String fomrattedNumber = aDF.format(d); 

In my opinion the second option suits best for your case.

Answer 3

The number created from parsed String has more fractional digits. But when you try to output it uses format's MaximumFractionDigits to create String from any given Number.