* [Java] add missing nullable judgement when required property is true
* [Java] add okhttp template test and regenerate sample
* [Java] add tests when field is nullable and required
* [Java] regenerate samples to fix pipeline error
* [Java] add JSONTest fro RequiredNullableBody class
* run generate-samples after rebase
* review feedback
* review feedback
* fix test
* update hash of test file
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Co-authored-by: weirdo0314 <2019215183@stu.cqupt.edu.cn>