java - UUID.randomUUID().getLeastSignificantBits() 总是返回负值？

Question

我需要生成一个唯一的 long 值，所以我决定使用 UUID:

UUID.randomUUID().getLeastSignificantBits();

我注意到一件奇怪的事情是 UUID.randomUUID().getLeastSignificantBits() 总是返回负值。我很迷惑。我错过了什么吗？

Answer 1

Wikipedia says :

Version 4 UUIDs use a scheme relying only on random numbers. This algorithm sets the version number (4 bits) as well as two reserved bits. All other bits (the remaining 122 bits) are set using a random or pseudorandom data source.

Version 4 UUIDs have the form xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where x is any hexadecimal digit and y is one of 8, 9, A, or B

所以最低有效部分的第一位将始终为 1，使其成为负数。