Here is a very useful java conversion table that I’ve created while preparing for the Sun Certified Java Programmer exam.
Java primitive conversions table
And here is a complete overview of the Golden rules of widening, boxing & varargs:
1. Primitive Widening > Boxing > Varargs.
2. Widening and Boxing (WB) not allowed.
3. Boxing and Widening (BW) allowed.
4. While overloading Widening + vararg and boxing + vararg are mutually exclusive of each other.
5. Widening between wrapper classes not allowed
6. Widening+varArgs & Boxing+varargs are individually allowed (but not allowed in overloaded version of method)
7. Boxing+Widening is preferred over Boxing+Varargs.
More explanation here.
