[yashdotdev13]

Summary

Adds a practical MapVector example to the Java documentation.

The example demonstrates:

• Creating a MapVector with BIGINT keys and INT values.
• Writing multiple key-value entries using UnionMapWriter.
• Reading entries using UnionMapReader.
• Managing the allocator and vector lifecycle with try-with-resources.

It also explains how MapVector supports different key and value data types.

Validation

• git diff --check passed.
• Sphinx HTML documentation build: [report result after running the build].

Related Issue

Closes #40

[github-actions]

Thank you for opening a pull request!

Please label the PR with one or more of:

• bug-fix
• chore
• dependencies
• documentation
• enhancement

Also, add the 'breaking-change' label if appropriate.

See CONTRIBUTING.md for details.

[yashdotdev13]

Hi maintainers,

The PR is a documentation-only contribution. The required PR-format check is asking for a label.

Could someone with repository permissions please apply the documentation label so the checks can proceed?

Thanks!

[lidavidm]

git diff --check passed.

This is not a test.

Sphinx HTML documentation build: [report result after running the build].

Were the docs built?

Additionally, the original issue refers to the Cookbook, which is at https://github.com/apache/arrow-cookbook.