Well, I'm not sure how you'd even read the bytes of the class file without some sort of "software". It's tempting to start to list hopelessly impractical and silly low-level procedures for doing this. But to save time, I'll assume you're willing to at least use basic tools provided with Sun's own JDK - namely,
javap. You can use this to convert a class file to a sort of assembly language for the JVM, which is described in the
JVM Specification. It's possible to look through this carefully and, using your own brain, figure out what a program is doing. Unfortunately it's also slow and tedious, and error-prone for most of us. Which is why people developed programs like JAD. So I'd say yes, it's possible - though I'm not sure why anyone would want to.
