title: Why this is not valid regular expression
body: <p>I am facing following exception while parsing this <code>'((([A-Z][,]+)+)([A-Z]?))|([A-Z]))'</code> regular expression </p>
  
  <pre><code>WARNING: Exception message: org.xml.sax.SAXParseException; systemId: file:/u/bin/jakarta-tomcat-5.5.7/webapps/MyService/schema/version/1.2.35/RequestSchema.xsd; 
  lineNumber: 1928; columnNumber: 38; InvalidRegex: Pattern value '((([A-Z][,]+)+)([A-Z]?))|([A-Z]))' is not a valid regular expression. The reported error was: 'Can't find resource for bundle java.util.PropertyResourceBundle, key parser.factor.0' at column '{2}'.
  com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:198)
  com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.error(ErrorHandlerWrapper.java:134)
  com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:437)
  com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.reportSchemaErr(XSDHandler.java:4124)
  com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.reportSchemaError(XSDHandler.java:4107)
  com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDAbstractTraverser.reportSchemaError(XSDAbstractTraverser.java:721)
  com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDSimpleTypeTraverser.getSimpleType(XSDSimpleTypeTraverser.java:406)
  com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDSimpleTypeTraverser.traverseSimpleTypeDecl(XSDSimpleTypeTraverser.java:163)
  com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDSimpleTypeTraverser.traverseGlobal(XSDSimpleTypeTraverser.java:104)
  com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.traverseSchemas(XSDHandler.java:1431)
  com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.parseSchema(XSDHandler.java:619)
  com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaLoader.loadSchema(XMLSchemaLoader.java:588)
  com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaLoader.loadGrammar(XMLSchemaLoader.java:555)
  com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaLoader.loadGrammar(XMLSchemaLoader.java:521)
  com.sun.org.apache.xerces.internal.jaxp.validation.XMLSchemaFactory.newSchema(XMLSchemaFactory.java:240)
  </code></pre>
  
  <p>Any help in this regard will be highly appreciated.</p>