remove processContext usage across examples (java and kotlin)

[stankiewicz]

• Remove legacy processContext usage across and replace it with argument provider
• context_line values are updated to the main methods or beginning of class

validation:

• executed many: MapElementsExample, FlatMapElementsExample, CreateExample, ViewExample, SumExample, MinExample, MaxExample, MeanExample, DistinctExample, ToStringExample, RegexExample, WindowExample, CountPerKeyExample,, SumPerKeyExample, MinPerKeyExample, MaxPerKeyExample, MeanPerKeyExample
• executed some Kotlin pipelines: DebuggingWordCount, WordCount
• cicd.py script in Playground CI Nightly - No Errors: The script did NOT throw the previous ValueError; 40 Valid Examples Found

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request modernizes the Apache Beam examples by migrating away from the deprecated ProcessContext API in favor of more explicit and type-safe parameter injection. These changes improve code clarity and align the examples with current best practices for writing DoFns in both Java and Kotlin.

Highlights

• Legacy API Removal: Removed usage of the legacy ProcessContext API across numerous Java and Kotlin examples, replacing it with modern argument providers like @element and OutputReceiver.
• Code Modernization: Updated DoFn implementations to use parameter-based injection for elements, side inputs, and timestamps, improving readability and maintainability.
• Documentation Updates: Updated context_line metadata in example files to reflect changes in code structure.

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[gemini-code-assist]

Code Review

This pull request updates numerous Java examples to align with the new DoFn.ProcessElement method signature, which now uses explicit annotations like @Element, @OutputReceiver, @SideInput, @Timestamp, and PaneInfo instead of ProcessContext. This refactoring affects a wide range of examples, including those demonstrating Iceberg, SQL, various core transforms, complete examples, data tokenization utilities, game examples, and cookbook examples. Additionally, the CsvConverters utility was refactored to introduce a new FailsafeElementToJsonWithHeadersFn for handling CSVs with headers, and the WriteToBigQuery and WriteToText utilities were updated to reflect the new DoFn parameter structure. Review feedback suggests removing an unused variable (headersView) in CsvConverters.java for code cleanup.

[Abacn]

What is the consideration to branching the DoFn here? Is necessary to have a separate DoFn with/without side input under recommended OutputReceiver pattern? Ideally we can avoid duplicated codes if possible

[stankiewicz]

@kennknowles to chip in. we discussed that it's anti-pattern to have nullable side input.

[github-actions]

Assigning reviewers:

R: @chamikaramj for label java.

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