java.lang.NumberFormatException and SystemDecimalSeparator

Having this error

java.lang.NumberFormatException: For input string: "20,00"
    at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2043)
    at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
    at java.lang.Double.parseDouble(Double.java:538)
    at com.agitech.autofaces.el.FormatUtil.parseDouble(FormatUtil.java:122)
    at com.agitech.erp.converter.DoubleConverter.getAsObject(DoubleConverter.java:27)

after reading decimal-separator-in-numberformat this, i try

public class FormatUtil {
    public static char ApplicationDecimalSeparator = ',';
    public static char SystemDecimalSeparator;
    static {        
        DecimalFormatSymbols symbols= DecimalFormatSymbols.getInstance();
        SystemDecimalSeparator = symbols.getDecimalSeparator();     
        symbols.setDecimalSeparator(ApplicationDecimalSeparator);
    }
    public final static Double parseDouble(String d){
        if (d==null)
            return 0.0;
        return Double.parseDouble( fixDecimalSeparator(d) );
    }
    public final static String fixDecimalSeparator(String d){
        if (SystemDecimalSeparator==ApplicationDecimalSeparator)
            return d;
        return d.replaceAll( ""+SystemDecimalSeparator, ""+ApplicationDecimalSeparator);
    }
}

finally the SystemDecimalSeparator is already the ',' so why this exception ?

Its probably expecting 20.00 but how to get and fix this separtor ?

Indeed i test and its expectiong "20.00" instead and the default SystemDecimalSeparator is already the ','