Looking at the Java Reflection API, we can learn some lessons about immutability.

There are tons of books and articles about how to design and write good Java code, but surprisingly little about the specific topic of API design. Here's a summary of what I've learnt on the subject from various sources and my own experience.

The Java language has always had the notion of marker interfaces. A problem with these is that if a parent class has the marker, all its children inevitably do too. On the other hand, marker annotations don't necessarily have this limitation. Here's how to define a marker that can be cancelled in a subclass.

JavaPolis is great! Lots of interesting people, lots of interesting sessions. Here are my experiences, with a summary of most of the sessions I attended.

The JavaPolis 2004 conference takes place in Antwerp, Belgium, the week of the 13th to the 17th of December. An excellent selection of speakers (plus your humble scribe) at a very affordable price.

A minor annoyance with Java generics is that you often end up repeating type parameters in a variable declaration and in the constructor invocation that initializes that variable. Defining a trivial static method allows you to avoid this.

All too often, developers think that documenting their new creations just means writing a detailed technical description of what it does. In a sense, they're explaining things to themselves. But what you really need to do is explain things to someone who's coming across your stuff for the first time.