Convert a String to Number - Java

Question

Hi, What is the easiest and correct way to convert a String number with commas (for example: 835,111.2) to a Double instance.

Thanks, Rod

Answer 1

Have a look at java.text.NumberFormat. For example:

import java.text.*;
import java.util.*;

public class Test
{
    // Just for the sake of a simple test program!
    public static void main(String[] args) throws Exception
    {
        NumberFormat format = NumberFormat.getInstance(Locale.US);

        Number number = format.parse("835,111.2");
        System.out.println(number); // or use number.doubleValue()
    }
}

Depending on what kind of quantity you're using though, you might want to parse to a BigDecimal instead. The easiest way of doing that is probably:

BigDecimal value = new BigDecimal(str.replace(",", ""));

or use a DecimalFormat with setParseBigDecimal(true):

DecimalFormat format = (DecimalFormat) NumberFormat.getInstance(Locale.US);
format.setParseBigDecimal(true);
BigDecimal number = (BigDecimal) format.parse("835,111.2");

Answer 2

Use java.text.DecimalFormat:

DecimalFormat is a concrete subclass of NumberFormat that formats decimal numbers. It has a variety of features designed to make it possible to parse and format numbers in any locale, including support for Western, Arabic, and Indic digits. It also supports different kinds of numbers, including integers (123), fixed-point numbers (123.4), scientific notation (1.23E4), percentages (12%), and currency amounts ($123). All of these can be localized.

Answer 3

The easiest is not always the most correct. Here's the easiest:

String s = "835,111.2";
// NumberFormatException possible.
Double d = Double.parseDouble(s.replaceAll(",",""));

I haven't bothered with locales since you specifically stated you wanted commas replaced so I'm assuming you've already established yourself as a locale with comma is the thousands separator and the period is the decimal separator. There are better answers here if you want correct (in terms of internationalization) behavior.

Answer 4

A link can say more than thousand words