Use DecimalFormat to get varying amount of decimal places

decimalformat, java, string

Solution

Create a method to generate a certain number of `#` to a string, like so:

public static String generateNumberSigns(int n) {

    String s = "";
    for (int i = 0; i < n; i++) {
        s += "#";
    }
    return s;
}

And then use that method to generate a string to pass to the `DecimalFormat` class:

double value = 1234.567890;
int numPlaces = 5;

String numberSigns = generateNumberSigns(numPlaces);
DecimalFormat fmt = new DecimalFormat ("0." + numberSigns);

System.out.println(fmt.format(value));

OR simply do it all at once without a method:

double value = 1234.567890;
int numPlaces = 5;

String numberSigns = "";
for (int i = 0; i < numPlaces; i++) {
    numberSigns += "#";
}

DecimalFormat fmt = new DecimalFormat ("0." + numberSigns);

System.out.println(fmt.format(value));

Problem

So I want to use the Decimal Format class to round numbers: ``` double value = 10.555; DecimalFormat fmt = new DecimalFormat ("0.##"); System.out.println(fmt.format(value)); ``` Here, the variable `value` would be rounded to 2 decimal places, because there are two `#`s. However, I want to round `value` to an unknown amount of decimal places, indicated by a separate integer called `numPlaces`. Is there a way I could accomplish this by using the Decimal Formatter? e.g. If `numPlaces = 3` and `value = 10.555`, `value` needs to be rounded to 3 decimal places

Original source