Why Long.toHexString(0xFFFFFFFF) returns ffffffffffffffff

Question

This is what I see in java, and it puzzles me.

Long.toHexString(0xFFFFFFFF) returns ffffffffffffffff

Similarly, 0xFFFFFFFF

Answer 1

Of course, Long in java is 64-bits long! 0xFFFFFFFF means -1 as an int, when written in 64 bits, it's ffffffffffffffff.

However, if the number were unsigned, the string would also be ffffffff [but there's no unsigned in java].