[jdk11u-dev] RFR: 8333837: [11u] HexPrinterTest.java javac compile fails illegal start of expression

[SendaoYan]

Hi all,
  The testcase `test/lib-test/jdk/test/lib/hexdump/HexPrinterTest.java` fails because of Java 11 doesn't support `var v = switch(String) { case String -> ... }` syntax. This testcase was backported by [JDK-8333837](https://bugs.openjdk.org/browse/JDK-8333837) from jdk15. This PR fix the syntax error to make the testcase work normally.
  Only change the testcase, the change has been verified, no risk.

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Commit messages:
 - 8333837: [11u] HexPrinterTest.java javac compile fails illegal start of expression

Changes: https://git.openjdk.org/jdk11u-dev/pull/2750/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2750&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333837
  Stats: 17 lines in 1 file changed: 10 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2750.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2750/head:pull/2750

PR: https://git.openjdk.org/jdk11u-dev/pull/2750