JDK5.0-b64
According to the spec for XMLGregorianCalendar.equals() but contrary to the spec for Object.equals() the mthod should throw NPE if an argument is null.

However if we invoke equals with null argument then NPE is not thrown. You reproduce it by following code:

import javax.xml.datatype.DatatypeConfigurationException;
import javax.xml.datatype.DatatypeFactory;
import javax.xml.datatype.XMLGregorianCalendar;


class test {

    public static void main(String [] args) throws Exception {
        DatatypeFactory factory = null;
        try {
            factory = DatatypeFactory.newInstance();
        } catch (DatatypeConfigurationException dce) {
            dce.printStackTrace();
        }

        XMLGregorianCalendar calendar =
                factory.newXMLGregorianCalendar();
        calendar.equals(null);
        System.out.println("OK");
    }
}

It should print stack trace but prints OK.

###@###.### 2005-03-11 14:03:16 GMT

integrated in tag JWSDP-1_6-b08
###@###.### 2005-05-02 23:04:18 GMT