I used to prefer dynamic languages (specifically Python, Common Lisp, and Ruby) over Java for my spare-time coding projects. That's changed recently and I've come to realize it's because of generics and the smart for-loop in Java 5.

Since Generics arrived in Java, my code has a much cleaner feel to it. Imagine a class for generating Atom feeds. Instead of the Python code:

    class Feed:
    [...]
      def get_entries():
        return entries
    

    interface Feed {
      Iterable<Entry> getEntries();
    }
    

Now I know immediately that what I will be getting can be shoved through a smart for-loop and the entries worked over like so:

    for (Entry e: getEntries()) {
      doSomething(e);
    }
    

I had a good idea that the Python code would return a List (because I can see the return statement) but I'd have to run my tests to be sure it worked. With Java 5, I have a better chance at build self-documenting interfaces. I really like that.

I should probably also admit that IntelliJ IDEA has completely changed how I program in Java. I used to code with the following steps:

1. make changes
2. compile and wait forever.
3. read compiler errors
4. fix

1. make changes
2. look at the sidebar for red
3. see red, go directly to the error
4. fix

Same amount of steps but because of incremental compilation it's a small fraction of the former time and I never leave my editor.

I'm sure I'll write some gushing blog posts about IDEA and Java 5 in a few weeks. Papa's got a new bag.