4 ms·

Been there. I remember fixing a performance bug ages ago where we had URL (or maybe some other address class) used as a key in a HashMap (which seemed like a pe

Been there. I remember fixing a performance bug ages ago where we had URL (or maybe some other address class) used as a key in a HashMap (which seemed like a perfectly valid thing to do with a value class). We were doing literally thousands of DNS lookups for what seemed like the most trivial algorithms. equals() and hashCode() are probably one of the weakest points of Java. While it seems like an obvious candidate for a contract, the issue has always been that one person ends up defining equality for everyone, when often different usecases will warrant different definitions of equality. Are objects equal if they have the same identity? If they have the same data? If they resolve to the same thing? It's easy enough to leave them unimplemented but the issue then is a lack of standard library support for providing custom hash and equality functions for Maps and Sets.

kjeetgill 7y ago
I agree! I get that it's easy to critique in hindsight but it's clear that they eventually solved this sort of thing well via the Comparable/Comparator relationship. It's less an issue so I get why it's been backlogged, but it's one that I'd love to see worked out.
- ben509 7y ago
  What's frustrating in hindsight is they knew the URL class was obviously terrible, but never made a serious effort to stop people using it. I'm fine with not breaking old jars, but they could have made newer javac's by default die with a notice "use -legacy to build this". Same thing with Date, Vector, all the broken thread semantics, you name it. These classes should have been relegated to a handful of ancient jars, they shouldn't keep popping up in modern Java because newbies have to learn a whole host of classes they aren't supposed to use.
  - kjeetgill 7y ago
    I sorta agree when in comes to Vector and some of the Thread stuff, but URL is only broken in gethashcode() and equals(). The rest of the class is perfectly fine. It's a great simple curl that takes you pretty far before you reach for a real http client lib.

kjeetgill 7y ago

I agree! I get that it's easy to critique in hindsight but it's clear that they eventually solved this sort of thing well via the Comparable/Comparator relationship. It's less an issue so I get why it's been backlogged, but it's one that I'd love to see worked out.

ben509 7y ago
What's frustrating in hindsight is they knew the URL class was obviously terrible, but never made a serious effort to stop people using it. I'm fine with not breaking old jars, but they could have made newer javac's by default die with a notice "use -legacy to build this". Same thing with Date, Vector, all the broken thread semantics, you name it. These classes should have been relegated to a handful of ancient jars, they shouldn't keep popping up in modern Java because newbies have to learn a whole host of classes they aren't supposed to use.
- kjeetgill 7y ago
  I sorta agree when in comes to Vector and some of the Thread stuff, but URL is only broken in gethashcode() and equals(). The rest of the class is perfectly fine. It's a great simple curl that takes you pretty far before you reach for a real http client lib.