Java equivalent of unsigned long long?

Nope, there is not. You'll have to use the primitive long data type and deal with signedness issues, or use a class such as BigInteger.

Starting Java 8, there is support for unsigned long (unsigned 64 bits). The way you can use it is:

Long l1 = Long.parseUnsignedLong("17916881237904312345");

To print it, you can not simply print l1, but you have to first:

String l1Str = Long.toUnsignedString(l1)

Then

System.out.println(l1Str);

I don't believe so. Once you want to go bigger than a signed long, I think BigInteger is the only (out of the box) way to go.