Fix issue eclipse-ee4j#1819 incorrect enum value name generation with…

… leading digits

The first character of an enum value name is checked whether it complies with isJavaIdentifierStart, if not an underscore prefix will be added to that name.

jaxb-ri/xjc/src/main/java/com/sun/tools/xjc/reader/xmlschema/SimpleTypeBuilder.java

@@ -674,6 +674,8 @@ private List<CEnumConstant> buildCEnumConstants(XSRestrictionSimpleType type, bo
 
                 if(name==null) {
                     StringBuilder sb = new StringBuilder();
+                    if (factValue.length()>0 && !Character.isJavaIdentifierStart(facetValue.charAt(0)))
+                        sb.append('_'); //Otherwise enum constants starting with digits will be renamed to VALUE_x
                     for( int i=0; i<facetValue.length(); i++) {
                         char ch = facetValue.charAt(i);
                         if(Character.isJavaIdentifierPart(ch))