# To Java Migration

> Migrate COBOL code to idiomatic Java, preserving business logic while following Java best practices.

Migrate COBOL code to idiomatic Java, preserving business logic while following Java best practices. Use for COBOL modernization projects.

- Page: https://ss33.ai/skills/openhands/to-java-migration-27843571476
- Publisher: openhands
- Category: [Software Development](https://ss33.ai/skills/category/software-development-t44z8z) › [Languages & frameworks](https://ss33.ai/skills/category/software-development-t44z8z/languages-and-frameworks-rgvrso)
- License: MIT
- Source: https://github.com/openhands/extensions/blob/cc7d059f3b0cdb1f1d83e41d25f06e76887e905b/plugins/cobol-modernization/skills/to-java-migration/SKILL.md

## Skill

SKILL.md: https://ss33.ai/api/v1/ss33/download/openhands/to-java-migration-27843571476

Migrate COBOL code to idiomatic Java, preserving all business logic.

## Code Style Requirements

Write idiomatic Java, NOT literal COBOL translations:
- Use Java conventions: camelCase names, standard collections (List, Map)
- Use Java standard library instead of rolling your own
- No god classes — split into cohesive, single-responsibility classes
- No TODO comments or stub implementations — fully implement everything

## Robustness Requirements

- Validate inputs at method entry (null checks, range validation)
- Use try-catch for all I/O and external operations
- Use try-with-resources for files, streams, connections
- Handle errors gracefully with meaningful messages

## Configuration Requirements

- No hardcoded file paths or credentials — use environment variables
- No magic numbers — use named constants
- Make limits and timeouts configurable

## Documentation Requirements

- Add COBOL references: `// COBOL equivalent: BNK1CRA.cbl 145-167`
- Document assumptions made during conversion
- Add Javadoc to public methods

## Testing Requirements

If test fixtures exist (see `cobol-build-setup` skill):
- Create a JUnit test class for each migrated program
- Load inputs from fixtures, assert output matches expected (golden) output
- All tests must pass before migration is complete

## References

- See [references/cobol-to-java-example.md](references/cobol-to-java-example.md) for a complete transformation example
- See [references/datatype-mappings.md](references/datatype-mappings.md) for COBOL→Java type mappings

## Done When

✓ Code compiles without errors
✓ All JUnit tests pass (Java output matches COBOL golden output)
✓ No TODO or stub implementations remain
✓ COBOL references documented in comments