[ISSUE #5298]Polish code style for jdk8+

[mxsm]

Make sure set the target branch to develop

What is the purpose of the change

close #5298

Brief changelog

• Polish code style for jdk8+
• Remove tools model test useless import

Verifying this change

build project after change

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[echooymxq]

RocketMQ base on java8, you did a great job. Actually, while i was reading the source code, there are many code smells, but I have no motivation to fix it.