Migrate COBOL Merge Sort to Java

[devin-ai-integration]

Migrate COBOL Merge Sort to Java

Summary

This PR implements a Java version of the COBOL merge sort program found in merge_sort/merge_sort_test.cbl. The Java implementation replicates the exact functionality and output format of the original COBOL program, including:

• Customer record structure: 5-digit customer ID, 50-char last/first names, 5-digit contract ID, 25-char comment
• Test data generation: Creates the same 11 customer records across two input files
• Merge operation: Combines two input files and sorts by customer ID (ascending)
• Sort operation: Sorts the merged file by contract ID (descending)
• File output: Generates merge-output.txt and sorted-contract-id.txt with identical formatting

The implementation uses a Customer class with proper field formatting and two main operations that mirror the COBOL merge and sort statements.

Review & Testing Checklist for Human

• Compare output files: Run both COBOL and Java versions and verify merge-output.txt and sorted-contract-id.txt are identical
• Verify record formatting: Check that Customer.toString() produces exact COBOL field widths (5+50+50+5+25 characters)
• Test edge cases: Try with empty/null fields, strings longer than field limits, and invalid data
• Validate sorting logic: Confirm merge sorts by customer ID ascending and final sort by contract ID descending
• Package structure review: Ensure the Java package structure (com.cognition.cobol.mergesort) is appropriate for the repository

Recommended test plan:

1. Run the original COBOL program and save outputs
2. Run java com.cognition.cobol.mergesort.MergeSortExample
3. Compare all generated files byte-for-byte
4. Test with modified input data to verify sorting behavior

---

Diagram

%%{ init : { "theme" : "default" }}%%
graph TD
    COBOL["merge_sort/merge_sort_test.cbl"]:::context
    Customer["java-merge-sort/com/cognition/<br/>cobol/mergesort/Customer.java"]:::major-edit
    Main["java-merge-sort/com/cognition/<br/>cobol/mergesort/MergeSortExample.java"]:::major-edit
    README["java-merge-sort/README.md"]:::major-edit
    
    TestFile1["test-file-1.txt"]:::minor-edit
    TestFile2["test-file-2.txt"]:::minor-edit
    MergeOutput["merge-output.txt"]:::minor-edit
    SortedOutput["sorted-contract-id.txt"]:::minor-edit
    
    COBOL -->|"replicates functionality"| Main
    Main -->|"uses"| Customer
    Main -->|"creates"| TestFile1
    Main -->|"creates"| TestFile2
    Main -->|"generates"| MergeOutput
    Main -->|"generates"| SortedOutput
    
    subgraph Legend
        L1[Major Edit]:::major-edit
        L2[Minor Edit]:::minor-edit  
        L3[Context/No Edit]:::context
    end

    classDef major-edit fill:#90EE90
    classDef minor-edit fill:#87CEEB
    classDef context fill:#FFFFFF

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Notes

• Link to Devin run: https://app.devin.ai/sessions/769714e0f3d34463886abd852d7b48b3
• Requested by: @ameen15 (Ameen from ameen@cognition.ai)
• Testing performed: Compiled and ran Java version, verified output matches expected COBOL behavior with all 11 test records
• Risk areas: Field formatting precision, string padding/truncation logic, and potential platform differences in file I/O

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