java.util.UUID.randomUUID().toString()length

java.util.UUID.randomUUID().toString()长度总是等于36吗？

我无法找到相关信息. Here只说以下内容：

public static UUID randomUUID()
Static factory to retrieve a type 4 (pseudo randomly generated) UUID. The UUID is generated using a cryptographically strong pseudo random number generator.
Returns:
A randomly generated UUID

那种类型4没有告诉我什么.我不知道在这种情况下4型是什么意思.

解决方法:

Does java.util.UUID.randomUUID().toString() length always equal to 36?

是！！它是.

UUID实际上是128位值(2长).要将128位表示为十六进制字符串,将有128/4 = 32个字符(每个字符长度为4位).在字符串格式中,它还包含4( – ),这就是长度为36的原因.

例如：54947df8-0e9e-4471-a2f9-9af509fb5889

32 hex char 4连字符char = 36 char.所以长度总是一样的.

更新：

I do not know what type 4 means in the case.?

  

仅供参考：有几种方法可以生成UUID.这里类型4表示使用随机或伪随机数生成此uuid.来自wiki – Universally_unique_identifier#Versions：

Versions

For both variants 1 and 2, five “versions” are defined in the standards, and each version may be more appropriate than the others in specific use cases. Version is indicated by the M in the string representation.

Version 1 UUIDs are generated from a time and a node id (usually the MAC address);

version 2 UUIDs are generated from an identifier (usually a group or user id), time, and a node id;

versions 3 and 5 produce deterministic UUIDs generated by hashing a namespace identifier and name;

and version 4 UUIDs are generated using a random or pseudo-random number.

标签：string-length,java,string,random,uuid
来源： https://codeday.me/bug/20190930/1836766.html