not found in classcomgooglegsonJsonNull

This error message suggests that the class 'com.google.gson.JsonNull' could not be found. This could be caused by a missing or incorrect dependency in your project.

You can try the following steps to resolve the issue:

1. Make sure that the correct version of the Gson library is added to your project's dependencies.

2. Check that the Gson library is included in your project's build path.

3. Clean and rebuild your project to ensure that all dependencies are properly resolved.

4. If you are using a build tool like Maven or Gradle, try deleting the local cache and rebuilding the project.

5. Check for any typos or errors in your code that could be causing the issue.

If none of these steps resolve the issue, you may need to seek further help from the Gson library community or your development team