RFR: 8263190: Update java.io, java.math, and java.text to use instanceof pattern variable

[Patrick Concannon]

Hi,

Could someone please review my code for updating the code in the `java.io`, `java.math`, and `java.text` packages to make use of the `instanceof` pattern variable?

Kind regards,
Patrick

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Commit messages:
 - 8263190: Update java.io, java.math, and java.text to use instanceof pattern variable

Changes: https://git.openjdk.java.net/jdk/pull/2879/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2879&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263190
  Stats: 60 lines in 15 files changed: 0 ins; 27 del; 33 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2879.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2879/head:pull/2879

PR: https://git.openjdk.java.net/jdk/pull/2879