This week's book giveaways are in the Scala and Android forums. We're giving away four copies each of Machine Learning Systems: Designs that scale and Xamarin in Action: Creating native cross-platform mobile apps and have the authors on-line! See this thread and this one for details.
The first [ always means it's an array. Next comes the type; I for int, B for byte, Z for boolean and L<class name>; for classes. So in this case, the [Ljava.lang.String; indicates it's a String array.
The part after the @ is the hexidecimal representation of the hash code.