Add Java rebuild of COBOL merge_sort_test.cbl

[devin-ai-integration]

Add Java rebuild of COBOL merge_sort_test.cbl

Summary

Rebuilds the COBOL merge_sort/merge_sort_test.cbl program as a Java 17 Maven project in merge_sort_java/. The original program creates two test data files (east/west customer records), merges them sorted by customer ID ascending, then re-sorts by contract ID descending — displaying results at each step. The Java version replicates this behavior using java.nio.file I/O and Comparator-based sorting.

Files added:

• CustomerRecord.java — data model with fixed-width (135-char) serialization matching the COBOL record layout (pic 9(5) + pic x(50) + pic x(50) + pic 9(5) + pic x(25))
• MergeSortExample.java — main program replicating the three COBOL paragraphs: create-test-data, merge-and-display-files, sort-and-display-file
• MergeSortExampleTest.java — 9 JUnit 4 tests covering record creation, merge order, sort order, field values, and round-trip serialization
• pom.xml — Maven build with Java 17, JUnit 4.13.2, executable JAR config

Review & Testing Checklist for Human

• Fixed-width format difference: COBOL pic 9(5) zero-pads numeric fields (e.g. 00001), but the Java String.format("%-5d", ...) space-pads left-aligned (e.g. 1 ). The round-trip parsing works because Integer.parseInt(str.trim()) handles both, but the on-disk file output is not byte-identical to what the COBOL program would produce. Verify this is acceptable.
• Test data accuracy: Spot-check that the hardcoded test records in createTestData() match the COBOL source values (customer IDs, names, contract IDs, comments).
• Run locally: Execute mvn clean test to confirm all 9 tests pass and the program produces the expected merge/sort output.

Test Plan

1. Clone the branch and navigate to merge_sort_java/
2. Run mvn clean test — should see Tests run: 9, Failures: 0, Errors: 0
3. Run mvn package && java -jar target/merge-sort-example-1.0.0.jar — should print test data creation, merged records sorted by ID, then re-sorted by contract ID descending, ending with "Done."
4. Inspect generated files (test-file-1.txt, test-file-2.txt, merge-output.txt, sorted-contract-id.txt) to verify fixed-width formatting and sort order

Notes

• The Java implementation uses in-memory List.sort() rather than a file-based merge algorithm, which is functionally equivalent for this data size but conceptually differs from COBOL's MERGE verb
• All tests pass locally with Maven 3.6.3 and Java 17
• Link to Devin run: https://app.devin.ai/sessions/d395486725224616910640b6136622fb
• Requested by: @joao-cognition

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