RFR: JDK-8322512 StringBuffer.repeat does not work correctly after toString() was called [v4]

[Jim Laskey]

> The new repeat methods were not clearing the toStringCache.

Jim Laskey has updated the pull request incrementally with one additional commit since the last revision:

  Nit in test

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17172/files
  - new: https://git.openjdk.org/jdk/pull/17172/files/33dd7973..ec72e77c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17172&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17172&range=02-03

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/17172.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17172/head:pull/17172

PR: https://git.openjdk.org/jdk/pull/17172