MINOR: Use statically compiled regular expressions instead of inline

[KoenDG]

This should improve performance, as in-place means that the regex has to be compiled again each time the code path is traversed. Which is not performant.

A nice writeup on this topic can be found here: https://softwareengineering.stackexchange.com/questions/216320/java-regex-patterns-compile-time-constants-or-instance-members

And it's also recommended in Joshua Bloch's "Effective Java 3rd Edition" (Item 6: Avoid creating unnecessary objects)

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[KoenDG]

Pinging @guozhangwang

Can you assign someone to look at this? Sorry to bother you, just saw you assigning someone in this PR: #4745

Also, the builds seem to be gone so I can't check code coverage for these changes. Though the resulting functionality should be identical.

[guozhangwang]

cc @ijuma for reviews.

[ijuma]

Thanks for the PR. The file Base64 has been removed so this needs to be rebased.

[KoenDG]

@ijuma Is it better if I rebase it, or just make a new PR on a new branch? So that it's 1 commit.

EDIT: Well, rebased it once I got home. Let me know if something else is needed.

EDIT2: Well hot damn, another conflict. I'll get to fixing it later.

[KoenDG]

Third time's the charm, let's hope.

[KoenDG]

Closing to make a new one. Too many rebases and merges with trunk. I prefer there to be just 1 commit if at all possible.