RFR: JDK-8283480: Make AbstractStringBuilder sealed

[Jim Laskey]

On Tue, 22 Mar 2022 00:01:59 GMT, Joe Darcy <darcy at openjdk.org> wrote:

> As part of updating the core libraries to be sealed, the package-access AbstractStringBuilder, implementation superclass of StringBuilder and StringBuffer, can be marked as sealed with those two subclasses on its permits list.

LGTM

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Marked as reviewed by jlaskey (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/7898