Implement COBOL Merge Sort Migration to Java

[devin-ai-integration]

Implement COBOL Merge Sort Migration to Java

Summary

This PR migrates the merge sort functionality from the COBOL program merge_sort_test.cbl to Java while maintaining the exact same file-based processing behavior and output format. The implementation creates a Java equivalent that processes customer records through the same two-phase operation: merging two sorted files by customer ID, then sorting the merged result by contract ID.

Key Components:

• CustomerRecord.java: Data model with fixed-width formatting matching COBOL record structure
• MergeSortProcessor.java: Main processing logic for file operations, merging, and sorting
• Test data generation that produces identical records to the COBOL program
• File-based I/O maintaining the original workflow (test-file-1.txt → test-file-2.txt → merge-output.txt → sorted-contract-id.txt)

Review & Testing Checklist for Human

• Verify output format matches COBOL exactly - Compare the generated files with expected COBOL output to ensure fixed-width formatting is identical
• Test record parsing edge cases - Verify the fromString method correctly handles records with varying field lengths and potential edge cases
• Validate sorting behavior - Confirm that ascending customer ID merge and descending contract ID sort produce the expected ordering
• Test with different data sets - Try running with modified test data to ensure the sorting and merging logic is robust
• Check error handling - Verify file I/O errors are handled gracefully and provide meaningful error messages

Recommended test plan: Run both the original COBOL program and the Java implementation, then compare all output files byte-by-byte to ensure identical results.

---

Diagram

%%{ init : { "theme" : "default" }}%%
graph TD
    COBOL["merge_sort_test.cbl"]:::context
    CustomerRecord["CustomerRecord.java"]:::major-edit
    MergeSortProcessor["MergeSortProcessor.java"]:::major-edit
    README["README.md"]:::major-edit
    
    TestFile1["test-file-1.txt"]:::context
    TestFile2["test-file-2.txt"]:::context
    MergeOutput["merge-output.txt"]:::context
    SortedOutput["sorted-contract-id.txt"]:::context
    
    COBOL -->|"migrated to"| MergeSortProcessor
    MergeSortProcessor -->|"uses"| CustomerRecord
    MergeSortProcessor -->|"creates"| TestFile1
    MergeSortProcessor -->|"creates"| TestFile2
    MergeSortProcessor -->|"merges to"| MergeOutput
    MergeSortProcessor -->|"sorts to"| 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

This implementation maintains the file-based approach from COBOL rather than converting to in-memory collections, ensuring the migration preserves the original processing behavior. The fixed-width record format uses exact field lengths (customer ID: 5 digits, names: 50 chars each, contract ID: 5 digits, comment: 25 chars) to match the COBOL PICTURE clauses.

Link to Devin run: https://app.devin.ai/sessions/aab675392d2146e8960646585a0d73d6
Requested by: Samir Chaudhry (@schaudhry123)

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