RFR: 8335802: Improve startup speed HexFormat uses boolean instead of enum

[Shaojin Wen]

The current HexFormat defines an Enum to represent LowerCase and UpperCase


class HexFormat {
    private enum Case {
        LOWERCASE,
        UPPERCASE
    }
}


This will cause the JVM to load one more class when it starts, which can be seen as follows


public class Startup {
    public static void main(String[] args) {}
}



java -verbose:class Startup



[0.094s][info][class,load] java.util.HexFormat$Case source: /Users/.../jdk/modules/java.base


There are only two cases here, which can be represented by boolean, which is clearer and can improve the startup speed a little bit.

-------------

Commit messages:
 - enum replaced by boolean, Reduce the number of classes loaded by startup

Changes: https://git.openjdk.org/jdk/pull/20060/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20060&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335802
  Stats: 24 lines in 1 file changed: 0 ins; 6 del; 18 mod
  Patch: https://git.openjdk.org/jdk/pull/20060.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20060/head:pull/20060

PR: https://git.openjdk.org/jdk/pull/20060