Refactor 20250116

[wenshao]

What this PR does / why we need it?

Summary of your change

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 82.97872% with 72 lines in your changes missing coverage. Please review.

Project coverage is 72.74%. Comparing base (eb28d51) to head (6913ae6).
Report is 12 commits behind head on main.

Files with missing lines	Patch %	Lines
...in/java/com/alibaba/fastjson2/JSONReaderJSONB.java	79.92%	14 Missing and 40 partials ⚠️
...in/java/com/alibaba/fastjson2/JSONWriterJSONB.java	88.11%	13 Missing and 4 partials ⚠️
...ore/src/main/java/com/alibaba/fastjson2/JSONB.java	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #3290      +/-   ##
============================================
- Coverage     74.29%   72.74%   -1.55%     
+ Complexity    23451    22730     -721     
============================================
  Files           668      668              
  Lines         89915    89301     -614     
  Branches      20337    20175     -162     
============================================
- Hits          66798    64964    -1834     
- Misses        14932    16042    +1110     
- Partials       8185     8295     +110     

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