<Swing Dev> RFR: 8264428: Cleanup usages of StringBuffer in java.desktop [v4]

[Andrey Turbanov]

> There are few possible cleanups in java.desktop related to legacy StringBuffer usages:
> 1. In few places StringBuffer can be replaced with plain String concatenation.
> 2. StringBuffer can be replaced with StringBuilder. StringBuilder has better performance as it is not thread-safe.
> 3. There are few places where result of string concatenation is passed to StringBuffer.append method. Using separate `.append` calls is more clear.
> 4. In few places primitives are unnecessary converted to String before `.append` call. They can be replaced with specialized methods (like `.append(int)` calls.

Andrey Turbanov has updated the pull request incrementally with one additional commit since the last revision:

  8264484: Replace uses of StringBuffer with StringBuilder in jdk.hotspot.agent
  
  place each 'append' call on its own line

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3251/files
  - new: https://git.openjdk.java.net/jdk/pull/3251/files/963dc56e..d083f953

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3251&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3251&range=02-03

  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3251.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3251/head:pull/3251

PR: https://git.openjdk.java.net/jdk/pull/3251