How to convert a scientific notation string to normal string

I have a below program which is reading and displaying decimal numbers.

import java.math.*;
import java.text.DecimalFormat;
import java.text.ParseException;

public class Main {
    public static void main (String[] args) {
      String valStr = "-5.36870912E+9";
      Object val = null;
      DecimalFormat mDecimalFormat = new DecimalFormat("#.#");
      mDecimalFormat.setParseBigDecimal(true);
      mDecimalFormat.setMaximumFractionDigits(38);
      try {
        val = new BigDecimal(mDecimalFormat.parse(valStr).toString());
        System.out.println("valStr = " + valStr + " val = " + val + " mDecimalFormat.parse(valStr) " + mDecimalFormat.parse(valStr));
      }
      catch (ParseException ee) {
          System.out.println("Caught Exception");
      }
  }
}

It generates a below output.

valStr = -5.36870912E+9 val = -5.36870912 mDecimalFormat.parse(valStr) -5.36870912

Here the issue is, parse ignores the exponential format.

I tried to use below code with BigDecimal and it works fine.

BigDecimal temp = new BigDecimal(valStr);
val = new BigDecimal(mDecimalFormat.parse(temp.toPlainString()).toString());
Output with above changes are 
valStr = -5.36870912E+9 val = -5368709120 mDecimalFormat.parse(valStr) -5.36870912

But the problem is, if I try to use inputs from different locale, For example, French as shown below.

String valStr = "-5,36870912E+9";
Ending up with below exception.
Exception in thread "main" java.lang.NumberFormatException: Character , is neither a decimal digit number, decimal point, nor "e" notation exponential mark.
    at java.base/java.math.BigDecimal.<init>(BigDecimal.java:522)
    at java.base/java.math.BigDecimal.<init>(BigDecimal.java:405)
    at java.base/java.math.BigDecimal.<init>(BigDecimal.java:838)
    at Main.main(Main.java:14)

I have referred various pages, most of the suggestions were to use BigDecimal, Double.

Is there any way i could convert the string "-5,36870912E+9" to "-5368709120" before calling parse method?