> If x is known to be a String, the type check succeeds; if x is known to be a Socket, the type check fails. So the author is trying to explain what the null p

> If x is known to be a String, the type check succeeds; if x is known to be a Socket, the type check fails. So the author is trying to explain what the null pointer exception is, but uses the concept of sockets in his example. I wonder, how many people know what a socket is but don't know what null pointer exception is?