Question

I have to convert a German locale formatted String to a BigDecimal. However, I’m struggling with the best solution.

The following code shows my problem:

    String numberString = "2.105,88";

    NumberFormat nf = NumberFormat.getInstance(Locale.GERMAN);
    try {
        Number parsed = nf.parse(numberString);
        BigDecimal bd1 = new BigDecimal(parsed.toString());
        System.out.println(bd1.toString());

        BigDecimal bd2 = new BigDecimal(parsed.doubleValue());
        System.out.println(bd2);

        BigDecimal bd3 = new BigDecimal(numberString);
        System.out.println(bd3);

    } catch (ParseException e) {
        e.printStackTrace();
    }

The outpout of this is

2105.88

2105.8800000000001091393642127513885498046875

Exception in thread “main” java.lang.NumberFormatException
at java.math.BigDecimal.(Unknown Source)
at java.math.BigDecimal.(Unknown Source)
at test.BigDecimalTest.main(BigDecimalTest.java:22)

The first output is correct, but it doesn’t really make sense to convert a String to a Number (Double to be precise), then back to a String again and then into a specific type of Number, BigDecimal.

The second output is incorrect, but could be solved by setting the scale of the BigDecimal. However, the amount of digits is not always known.

The third output is obviously not what I’m looking for.

My question: What would be the best way? Are there better ways to do this?

Answer 1

It seems like there is no other way since java.Lang.Number doesn’t have a method which returns a BigDecimal type. Anyway it makes sense because BigDecimal only accepts strings which are properly formatted not like "2.105,88" but like "2105.88".

Let me show your my code:

import java.math.BigDecimal;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.text.ParseException;
import java.util.Locale;
public class JavaMain {
    public static void main(String[] args) {
        String numberString = "2.105,88";
        //using casting
        try {
            DecimalFormat df = (DecimalFormat) NumberFormat.getInstance(Locale.GERMAN);
            df.setParseBigDecimal(true);
            BigDecimal bd = (BigDecimal) df.parseObject(numberString);
            System.out.println(bd.toString());
        } catch (ParseException e) {
            e.printStackTrace();
        }
        //your way short version
        NumberFormat nf = NumberFormat.getInstance(Locale.GERMAN);
        try {
            BigDecimal bd1 = new BigDecimal(nf.parse(numberString).toString());
            System.out.println(bd1.toString());
        } catch (ParseException e) {
            e.printStackTrace();
        }
        String numberStringFixed = "2105.88";
        //direct string formatted
        System.out.println(new BigDecimal(numberStringFixed));;     
        //direct but erroneous way if the string is not formatted
        System.out.println(new BigDecimal(numberString));;
        
    }
}

I hope this helps!