Exception only occuring during stress test

Question

We are trying to get ready to release a beta version of the software I'm working on.. so part of getting ready for that was to try set up some stress tests and hit the server with multiple requests for the same page....
Not sure exactly how many it is taking but we are getting the following exception.
2005-06-10 13:20:23 StandardWrapperValve[action]: Servlet.service() for servlet action threw exception
java.lang.NumberFormatException: For input string: "200044.E2000444E"
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
        at java.lang.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1207)
        at java.lang.Double.parseDouble(Double.java:220)
        at java.text.DigitList.getDouble(DigitList.java:127)
        at java.text.DecimalFormat.parse(DecimalFormat.java:1070)
        at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1386)
        at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1156)
        at java.text.DateFormat.parse(DateFormat.java:333)
        at com.xxxxx.xxxxx.struts.adapter.BrowseBaseAdapter.formatYyyyMMddToLocaleStr(BrowseBaseAdapter.java:194)I can only assume that something was not thread safe and somehow something is getting confused....
this is the method that produced the error and the code that it runs.
I know absolutely nothing about making something thread safe.... can anyone give me good link to refer to or point something out in the below code that might be a no no.
private static final SimpleDateFormat xxxxxxxxDateFormat =
          new SimpleDateFormat("yyyyMMdd");
     protected String formatYyyyMMddToLocaleStr(
          String  xxxxxxxxDt,
          Locale locale) {
          String result = "";
          if ( xxxxxxxxDt != null &&  xxxxxxxxDt.length() == 8) {
               try {
                    Date tempDate =  xxxxxxxxDateFormat.parse( xxxxxxxxDt);
                    result = javaDataTypeToString(tempDate, locale);
               } catch (ParseException ex) {
          return result;
public String javaDataTypeToString(Object data, Locale locale) {
          String returnType = data.getClass().getName();
          String result = null;
          if (returnType.equals("java.lang.String")) {
               result = (String) data;
          } else if (returnType.equals("java.lang.Float")) {
               NumberFormat formatter = NumberFormat.getNumberInstance(locale);
               formatter.setMaximumFractionDigits(6);
               formatter.setGroupingUsed(false);
               result = formatter.format((Float) data);
          } else if (returnType.equals("java.lang.Double")
                    || returnType.equals("java.math.BigDecimal")) {
               NumberFormat formatter = NumberFormat.getNumberInstance(locale);
               formatter.setMaximumFractionDigits(13);
               formatter.setGroupingUsed(false);
               StringBuffer buffer = new StringBuffer();
               result = formatter.format(data, buffer, new FieldPosition(0))
                         .toString();
          } else if (returnType.equals("java.lang.Integer")) {
               Integer inte = (Integer) data;
               int intVal = inte.intValue();
               if (intVal != 0)
                    result = String.valueOf(intVal);
               else
                    result = "";
          } else if (returnType.equals("java.util.Date")) {
               java.util.Date date = (java.util.Date) data;
               SimpleDateFormat dateFormatter = getDatePattern(locale);
               result = dateFormatter.format(date);
          } else if (returnType.equals("com.sungard.stnweb.utility.Time")) {
               Time time = (Time) data;
               result = time.asString();
          } else if (returnType.equals("java.lang.Boolean")) {
               Boolean dataBool = (Boolean) data;
               if (dataBool.booleanValue())
                    result = "1";
               else
                    result = "";
          return result;

Answer 1

From the API on java.text.SimpleDateFormat
Synchronization
Date formats are not synchronized. It is recommended to create separate
format instances for each thread. If multiple threads access a format
concurrently, it must be synchronized externally. Being static, your date format object will be accessed by multiple threads.
Solution: Don't make the date format object static.
I would suggest like this:
private static final String dfString  ="yyyyMMdd";
protected String formatYyyyMMddToLocaleStr(String  xxxxxxxxDt, Locale locale) {
  String result = "";
  SimpleDateFormat xxxxxxxxDateFormat = new SimpleDateFormat(dfString );
  if ( xxxxxxxxDt != null &&  xxxxxxxxDt.length() == 8) {
  try {
    Date tempDate =  xxxxxxxxDateFormat.parse( xxxxxxxxDt);
    result = javaDataTypeToString(tempDate, locale);
  catch (ParseException ex) {}
          return result;
Ok, so it is constructing a DateFormatting object for each method call, but I don't see it as that big a deal. Its not a huge hit. You might get away with making it an instance variable - I don't know how you use the enclosing class. Start with this, and see if it works.
Cheers,
evnafets