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 an equivalent Java Maven project under merge_sort_java/. The COBOL program creates two customer data files (East/West), merges them sorted by ascending customer ID, then re-sorts the merged result by descending contract ID — all using fixed-width 135-char records. The Java version mirrors this behavior using CustomerRecord with matching field widths (pic 9(5) → %05d, pic x(50) → %-50s, etc.), file I/O via BufferedReader/BufferedWriter, and Comparator-based sorting.

Files added:

• pom.xml — Maven build with Java 17, JUnit 4, executable JAR config
• CustomerRecord.java — Record class with fixed-width serialization/deserialization and comparators
• MergeSortExample.java — Main class: creates test data, merges, sorts, displays
• MergeSortExampleTest.java — 5 JUnit tests covering data creation, merge, sort, record round-trip, and full run

Review & Testing Checklist for Human

• Verify test data values match COBOL source exactly — the hardcoded East (6 records) and West (5 records) data in createTestData() should match merge_sort_test.cbl lines 185–334. Spot-check a few records (e.g., customer 999 has contract 1610, comment "comment-99")
• Verify fixed-width field layout matches COBOL record structure — toFileString/fromFileString use offsets 0-5, 5-55, 55-105, 105-110, 110-135 which should correspond to the COBOL pic definitions (5 + 50 + 50 + 5 + 25 = 135)
• Run mvn clean test in merge_sort_java/ and optionally mvn exec:java or java -jar target/*.jar to see console output matches expected COBOL merge/sort order
• Check that the COBOL MERGE on unsorted inputs is functionally equivalent to Java's concat-and-sort approach — COBOL's MERGE implicitly sorts, so both should produce the same result

Notes

• The COBOL program does not pre-sort input files before merging; the MERGE statement handles that. The Java equivalent concatenates both lists and sorts, which is functionally identical.
• CustomerRecord.equals/hashCode will NPE on null fields — acceptable here since all data is non-null, but not defensive.
• No COBOL runtime was available to produce reference output, so correctness is based on reading the COBOL source.

Link to Devin run: https://app.devin.ai/sessions/dce91d18176d4d08a0ac2c173c79b862
Requested by: @joao-cognition

[devin-ai-integration]

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