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Description

The code style of using com.alibaba.fluss.utils.Preconditions is not consistent in Fluss. Some may use static imports (checkNotNull(...);), some may use class imports (Preconditions.checkNotNull(...);).

We have a Preconditions static importing rule in checksytle, but that is for Guava Preconditions, and Guava Preconditions was forbidden and suggested to use Fluss Precondition.

We just need to update the checkstyle rule to fit Fluss Precondition, and update all the class imports in the codebase.

        <module name="RegexpSinglelineJava">
            <property name="format" value="^import com.alibaba.fluss.utils.Preconditions;$"/>
            <property name="message" value="Static import functions from Fluss Preconditions"/>
        </module>

Willingness to contribute

• I'm willing to submit a PR!