<Swing Dev> RFR: 8263768: JFormattedTextField.AbstractFormatter.getDocumentFilter()/getNavigationFilter() spec doesn't mention what the default impls return and what does it mean

[Prasanta Sadhukhan]

Default implementation of JFormattedTextField.AbstractFormatter.getDocumentFilter()/getNavigationFilter() returns null but it is not mentioned in the spec.
It is now explicitly mentioned in the spec by @impNote tag.

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Commit messages:
 - 8263768: JFormattedTextField.AbstractFormatter.getDocumentFilter()/getNavigationFilter() spec doesn't mention what the default impls return and what does it mean

Changes: https://git.openjdk.java.net/jdk/pull/3064/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3064&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263768
  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3064.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3064/head:pull/3064

PR: https://git.openjdk.java.net/jdk/pull/3064