I always hate when I’m reminded why I don’t like some technology. Today I was working with Java 5 and specifically a pre-Java 5 xml_rpc API similar to Apache XML-RPC. I made some incorrect assumptions about the return value of a particular rpc call. I was confident that it returned an array of strings (which is translated into a list of strings in Java) - but in fact it returns an array of structs (which is translated into a list of maps).