XOM API for Processing XML with Java

[John Cowan <jcowan AT reutershealth.com>]

Remko Popma scripsit:

> 1) Is this really a typesafe enum issue?
> Basically, as far as I understand it, neither the == operator nor the
> equals() method works if you compare two instances loaded by separate
> classloaders. So eg. someNode.equals(sameNodeLoadedByOtherClassloader)
> would also return false. 

Typesafe enums are in competition with plain old integers, which don't care
about class loaders.  So yes, it's a typesafe enum issue in that you don't
get the expected results with enums whereas you do with ints.

Here's a possibility:

        int theCode;

        private SomeEnumClass(int code) {theCode = code;}
        public int hashCode {return theCode;}
        public boolean equals(Object o) {
                if 
(!o.getClass().getName().equals("blah.blah.SomeEnumClass")) {
                        return false;
                        }
                else {
                        return theCode == o.hashCode();
                        }

Note the importance of testing the class *name* for equality, not the
class object.  That way, we do the hashCode check iff this is the same
class independent of class loaders.

-- 
John Cowan                                <jcowan AT reutershealth.com>     
http://www.reutershealth.com              http://www.ccil.org/~cowan
Yakka foob mog.  Grug pubbawup zink wattoom gazork.  Chumble spuzz.
    -- Calvin, giving Newton's First Law "in his own words"