Best way to parseDouble with comma as decimal separator?

Question

Following is resulting in an Exception:

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

Is there a bet

Answer 1

Double.parseDouble(p.replace(',','.'))

...is very quick as it searches the underlying character array on a char-by-char basis. The string replace versions compile a RegEx to evaluate.

Basically replace(char,char) is about 10 times quicker and since you'll be doing these kind of things in low-level code it makes sense to think about this. The Hot Spot optimiser will not figure it out... Certainly doesn't on my system.

Answer 2

In Kotlin you can use extensions as below:

fun String.toDoubleEx() : Double {
   val decimalSymbol = DecimalFormatSymbols.getInstance().decimalSeparator
  return if (decimalSymbol == ',') {
      this.replace(decimalSymbol, '.').toDouble()
  } else {
      this.toDouble()
  }
}

and you can use it everywhere in your code like this:

val myNumber1 = "5,2"
val myNumber2 = "6.7"

val myNum1 = myNumber1.toDoubleEx()
val myNum2 = myNumber2.toDoubleEx()

It is easy and universal!

Answer 3

This would do the job:

Double.parseDouble(p.replace(',','.')); 

Answer 4

This is the static method I use in my own code:

public static double sGetDecimalStringAnyLocaleAsDouble (String value) {

    if (value == null) {
        Log.e("CORE", "Null value!");
        return 0.0;
    }

    Locale theLocale = Locale.getDefault();
    NumberFormat numberFormat = DecimalFormat.getInstance(theLocale);
    Number theNumber;
    try {
        theNumber = numberFormat.parse(value);
        return theNumber.doubleValue();
    } catch (ParseException e) {
        // The string value might be either 99.99 or 99,99, depending on Locale.
        // We can deal with this safely, by forcing to be a point for the decimal separator, and then using Double.valueOf ...
        //http://stackoverflow.com/questions/4323599/best-way-to-parsedouble-with-comma-as-decimal-separator
        String valueWithDot = value.replaceAll(",",".");

        try {
          return Double.valueOf(valueWithDot);
        } catch (NumberFormatException e2)  {
            // This happens if we're trying (say) to parse a string that isn't a number, as though it were a number!
            // If this happens, it should only be due to application logic problems.
            // In this case, the safest thing to do is return 0, having first fired-off a log warning.
            Log.w("CORE", "Warning: Value is not a number" + value);
            return 0.0;
        }
    }
}