Reduce Java SDK's size

**Is your feature request related to a problem? Please describe.**
Current SDK will occupy around 250MB. Which is a lot larger than the sum of other packages in our user code. I think this may put potential user away.

**Describe the solution you'd like**
<= 5M would be more reasonable.

The issue is about reducing the Java SDK size from ~250MB to <=5MB. Start by examining the Java SDK build configuration and dependencies in the repository. Look for large dependencies or bundled resources that can be removed or optimized. Check the project's build system (likely Maven or Gradle) and analyze the final JAR size. Determine what constitutes the SDK and identify areas for size reduction, such as removing unused dependencies, optimizing resources, or using lighter alternatives.

Written by the indexing model from the issue text.