RFR: 8255934: JConsole 14 and greater fails to connect to older JVM

Mon Nov 16 23:05:10 UTC 2020

OperatingSystemMXBean was changed in jdk14 (see JDK-8226575):
New methods getTotalMemorySize and getFreeMemorySize were added, old getTotalPhysicalMemorySize and getFreePhysicalMemorySize were deprecated.

The fix adds fallbacks for the values (i.e. if new methods fail, jconsole calls old methods)

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

Commit messages:
 - Adds fallback getters

Changes: https://git.openjdk.java.net/jdk/pull/1243/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1243&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255934
  Stats: 22 lines in 1 file changed: 20 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1243.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1243/head:pull/1243

PR: https://git.openjdk.java.net/jdk/pull/1243