RFR: 8264484: Replace uses of StringBuffer with StringBuilder in jdk.hotspot.agent

[Aleksey Shipilev]

On Tue, 30 Mar 2021 19:41:32 GMT, actuallyasmartname <github.com+77011692+actuallyasmartname at openjdk.org> wrote:

>> Found by IntelliJ IDEA inspection `Java | Java language level migration aids | Java 5 | 'StringBuffer' may be 'StringBuilder'`
>> As suggested in https://github.com/openjdk/jdk/pull/1507#issuecomment-757369003 I've created separate PR for module `jdk.hotspot.agent`
>> Similar cleanups in the past: https://bugs.openjdk.java.net/browse/JDK-8041679 https://bugs.openjdk.java.net/browse/JDK-8264029
>
> Marked as reviewed by actuallyasmartname at github.com (no known OpenJDK username).

Created https://bugs.openjdk.java.net/browse/JDK-8264484 for it.

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PR: https://git.openjdk.java.net/jdk/pull/3275