If you are referring to Head First then you must have come across the sentence that JVM does automatic boxing on your behalf. If you are not referring that book then by now, its known to you. Yes, Java does automatic boxing (Wrap a varible inside a matching object). In this ex, when a byte value, a simple varible (5), is passed as a argument, it goes n sits in the Object type. This is the the place 'boxing' is done automatically. Then this Object is casted to Byte type object. Hope this helps.