Why does `instanceof` error rather than return `false` when used for 2 incompatible classes?

Question

I\'m reading this:
http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#15.20.2

They say:

Consider the example program

Answer 1

instanceof check is a runtime check. The compiler is able to discover that this condition is incorrect at compile time (much earlier), so it tells you that it is wrong. Always remember, that failing fast is a good practice, it will save you a lot of time and nerves.