RFR: 8263233: Update java.net and java.nio to use instanceof pattern variable

[Patrick Concannon]

Hi,

Could someone please review my code for updating the code in the `java.net` and `java.nio` packages to make use of the `instanceof` pattern variable?

Kind regards,
Patrick

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Commit messages:
 - 8263233: Update java.net and java.nio to use instanceof pattern variable

Changes: https://git.openjdk.java.net/jdk/pull/2890/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2890&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263233
  Stats: 65 lines in 17 files changed: 0 ins; 28 del; 37 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2890.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2890/head:pull/2890

PR: https://git.openjdk.java.net/jdk/pull/2890