How to use Java's DecimalFormat for “smart” currency formatting?

Question

I\'d like to use Java\'s DecimalFormat to format doubles like so:

#1 - 100 -> $100
#2 - 100.5 -> $100.50
#3 - 100.41 -> $100.41

Th

Answer 1

Use NumberFormat:

NumberFormat n = NumberFormat.getCurrencyInstance(Locale.US); 
double doublePayment = 100.13;
String s = n.format(doublePayment);
System.out.println(s);

Also, don't use doubles to represent exact values. If you're using currency values in something like a Monte Carlo method (where the values aren't exact anyways), double is preferred.

See also: Write Java programs to calculate and format currency

Answer 2

You can check "is number whole or not" and choose needed number format.

public class test {

  public static void main(String[] args){
    System.out.println(function(100d));
    System.out.println(function(100.5d));
    System.out.println(function(100.42d));
  }

  public static String function(Double doubleValue){
    boolean isWholeNumber=(doubleValue == Math.round(doubleValue));
    DecimalFormatSymbols formatSymbols = new DecimalFormatSymbols(Locale.GERMAN);
    formatSymbols.setDecimalSeparator('.');

    String pattern= isWholeNumber ? "#.##" : "#.00";    
    DecimalFormat df = new DecimalFormat(pattern, formatSymbols);
    return df.format(doubleValue);
  }
}

will give exactly what you want:

100
100.50
100.42

Answer 3

printf also works.

Example:

double anyNumber = 100; printf("The value is %4.2f ", anyNumber);

Output:

The value is 100.00

4.2 means force the number to have two digits after the decimal. The 4 controls how many digits to the right of the decimal.

Answer 4

You could use the Java Money API to achieve this. (although this is not using DecialFormat)

long amountInCents = ...;
double amountInEuro = amountInCents / 100.00;

String customPattern; 
if (minimumOrderValueInCents % 100 == 0) {
    customPattern = "# ¤";
} else {
    customPattern = "#.## ¤";
}

Money minDeliveryAmount = Money.of(amountInEuro, "EUR");
MonetaryAmountFormat formatter = MonetaryFormats.getAmountFormat(AmountFormatQueryBuilder.of(Locale.GERMANY)
            .set(CurrencyStyle.SYMBOL)
            .set("pattern", customPattern)
            .build());

System.out.println(minDeliveryAmount);