Parsing Double with Comma Decimal Separator

In Java, using the default NumberFormat can lead to errors when parsing strings with commas as decimal separators. Consider the following code:

String p = "1,234";
Double d = Double.valueOf(p); 
System.out.println(d);

This code will throw a NumberFormatException. To overcome this issue, a convenient solution would be to replace the comma with a period using p.replaceAll(",", "."). However, is there a more efficient way?

Better Parsing Method with java.text.NumberFormat

The java.text.NumberFormat class offers a sophisticated solution. It allows you to specify the locale-specific formatting rules, ensuring that the decimal separator is recognized correctly. Here's how to use NumberFormat:

NumberFormat format = NumberFormat.getInstance(Locale.FRANCE);
Number number = format.parse("1,234");
double d = number.doubleValue();

In this code, we instantiate a NumberFormat for the French locale, where the comma is used as a decimal separator. The parse() method converts the string to a Number object, which we then convert to a double using doubleValue().

Multi-Language Support

To support multi-language applications, use the following code:

NumberFormat format = NumberFormat.getInstance(Locale.getDefault());

This will create a NumberFormat for the default locale, which is the locale of the current user's operating system.