What are the other NaN values?

Question

The documentation for java.lang.Double.NaN says that it is

A constant holding a Not-a-Number (NaN) value of type double. It is equivalent

Answer 1

Java uses IEEE 754 for its floating point numbers and therefore follows their rules.

According to the Wikipedia page on NaN it is defined like this:

A bit-wise example of a IEEE floating-point standard single precision NaN: x111 1111 1axx xxxx xxxx xxxx xxxx xxxx where x means don't care.

So there are quite a few bit-patterns all of which are NaN values.