Help needed to convert dart code into java

Kindly go into main.dart and see the code. It uses the post method. Go and check server.py if needed.
Go to project-av.onrender.com to see what i wanted to do in my android app which i'm building using java.

Examine main.dart to understand the POST request logic and data structures. Review server.py to see the expected API endpoints and data format. The goal is to replicate the Dart functionality in Java for an Android app, but the issue lacks specific requirements or error details.

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