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20060213 Monday February 13, 2006

URL.hashCode() Busted?

I did a double take on this: 

        HashSet set = new HashSet();
        set.add(new URL("http://postsecret.blogspot.com"));
        set.add(new URL("http://dorion.blogspot.com"));
        for (Iterator it = set.iterator(); it.hasNext();) {
            System.out.println(it.next());
        }
I was expecting to get output like 
http://postsecret.blogspot.com
http://dorion.blogspot.com
or 
http://dorion.blogspot.com
http://postsecret.blogspot.com
But all that I got was 
http://postsecret.blogspot.com

Hmmm....

The java.net.URL javadoc says what I'd expect "Creates an integer suitable for hash table indexing." So I tried this: 

        URL url1 = new URL("http://postsecret.blogspot.com");
        URL url2 = new URL("http://dorion.blogspot.com");
        System.out.println(url1.hashCode() + " " + url1);
        System.out.println(url2.hashCode() + " " + url2);
and got this 
1117198397 http://postsecret.blogspot.com
1117198397 http://dorion.blogspot.com
I was expecting different hashCode's. Either java.net.URL is busted or I'm blowing it and my understanding of the contract with java.lang.Object and its hashCode() method is busted.

( Feb 13 2006, 07:37:29 PM PST ) Permalink