Special characters ("+", "-", "*") in Enumeration not Generated Correctly from Schema

<xsd:simpleType name="FormulaOperatorDataType">
<xsd:restriction base="xsd:string">
<xsd:enumeration value="-"/>
<xsd:enumeration value="+"/>
<xsd:enumeration value="*"/>
</xsd:restriction>
</xsd:simpleType>

The above snippet of an XML Schema will not be generated correctly when you try to generate classes. The below code snippets result:
/**

• The * type
  */
  public static final int __TYPE = 2;

/**

• The instance of the * type
  */
  public static final FormulaOperatorDataType _ = new FormulaOperatorDataType(__TYPE, "*");

...

private static java.util.Hashtable init()
{
Hashtable members = new Hashtable();
members.put("-", _);
return members;
} //-- java.util.Hashtable init()