Hashtable was used only from single thread. And only non-null key/values added to it. We can safely replace it with HashSet.
------------- Commit messages: - [PATCH] Unnecessary HashTable usage in StyleSheet Changes: https://git.openjdk.org/jdk/pull/10522/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10522&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8295323 Stats: 18 lines in 1 file changed: 0 ins; 2 del; 16 mod Patch: https://git.openjdk.org/jdk/pull/10522.diff Fetch: git fetch https://git.openjdk.org/jdk pull/10522/head:pull/10522 PR: https://git.openjdk.org/jdk/pull/10522
