Convert COBOL merge_sort_test.cbl to Java (MBA-18)

[devin-ai-integration]

Convert COBOL merge_sort_test.cbl to Java (MBA-18)

Summary

Converted the COBOL program merge_sort/merge_sort_test.cbl to functionally equivalent Java code (MergeSortExample.java). The Java implementation replicates all three main procedures from the COBOL program:

1. createTestData(): Creates two test files with hardcoded customer records (6 records in test-file-1.txt, 5 in test-file-2.txt)
2. mergeAndDisplayFiles(): Merges both files sorted by ascending customer ID → merge-output.txt, then displays records
3. sortAndDisplayFile(): Sorts merged file by descending contract ID → sorted-contract-id.txt, then displays records

Also added README.md with comprehensive documentation explaining both programs, compilation instructions, and verification steps.

Key Implementation Details:

• CustomerRecord class with fixed-width formatting matching COBOL PIC clauses:
  • Customer ID: pic 9(5) → 5-digit zero-padded integer
  • Last Name: pic x(50) → 50-char right-padded string
  • First Name: pic x(50) → 50-char right-padded string
  • Contract ID: pic 9(5) → 5-digit zero-padded integer
  • Comment: pic x(25) → 25-char right-padded string
• Total record length: 135 characters per line
• Uses Java Collections framework with Comparators for sorting operations
• File I/O uses BufferedReader/BufferedWriter for line sequential organization
• Error handling via IOException with System.exit(1) (equivalent to COBOL's file status checks)

Review & Testing Checklist for Human

⚠️ CRITICAL: I tested the Java program locally and verified it runs successfully with correct output formatting and sorting, but I did NOT run the COBOL program and compare outputs side-by-side. This verification is essential before merging.

• Run both COBOL and Java programs and compare outputs byte-for-byte - This is the most critical test to ensure functional equivalence

  # Follow the verification steps in README.md
  # All output files and console output must be identical

• Verify fixed-width formatting character-by-character - Check that each record is exactly 135 characters with correct field widths and padding
  • Numbers should be zero-padded on the left (e.g., 00001, 05423)
  • Strings should be space-padded on the right
  • Use a hex editor or character count to verify exact lengths
• Verify hardcoded test data matches COBOL source exactly - I manually transcribed 11 customer records from the COBOL source; double-check these values:
  • File 1: Customer IDs 1, 5, 10, 50, 25, 75 with their respective contract IDs, names, and comments
  • File 2: Customer IDs 999, 3, 30, 85, 24 with their respective contract IDs, names, and comments
• Verify sorting behavior - Confirm merge sorts ascending by customer ID and final sort is descending by contract ID
  • Expected merge order: 1, 3, 5, 10, 24, 25, 30, 50, 75, 85, 999
  • Expected final order by contract ID: 12323, 8765, 7725, 5423, 5050, 4567, 3331, 1610, 1175, 653, 247
• Test error handling - Try running with read-only files or insufficient disk space to ensure errors are caught appropriately

Notes

• Requested by: @ibrahim-sowunmi
• JIRA Ticket: MBA-18
• Link to Devin run: https://app.devin.ai/sessions/e99d69a02c5f44baad2eb0e9dfa160b6
• Testing Status: Java program tested locally in isolation; side-by-side comparison with COBOL program output still required
• File paths are relative (same directory as execution), matching COBOL behavior
• No automated tests were created; functional equivalence verification relies on manual comparison

[devin-ai-integration]

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[ibrahim-sowunmi]

Explain the code in this repo and generate a readme.

[devin-ai-integration]

I've added a comprehensive README.md to the merge_sort directory that explains:

• Program Overview: What both the COBOL and Java versions do
• Record Structure: The 135-character fixed-width format with all field details
• Compilation & Execution: Step-by-step instructions for both languages
• Program Flow: Detailed explanation of the three-step process (create test data, merge/sort by customer ID, sort by contract ID)
• Java Implementation Details: Class structure, design choices, and key implementation decisions
• Verification Steps: How to compare outputs between COBOL and Java versions

The README is now part of this PR. Let me know if you'd like me to add any additional details or clarifications!