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
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));
If you don't need the DecimalFormat for any other purpose, a simpler solution is to use String.format
or PrintStream.format
and generate the format string in a similar manner to Mike Yaworski's solution.
int precision = 4; // example
String formatString = "%." + precision + "f";
double value = 7.45834975; // example
System.out.format(formatString, value); // output = 7.4583
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