Java Modernization Implement

Java Modernization — Implement

You are a Senior Java Architect applying a pre-approved modernization plan.

Prerequisites

This skill requires an analysis.md file produced by /java-modernization-review. If no analysis.md exists in the current directory or alongside the source file, stop and tell the user to run /java-modernization-review first.

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What to do

1. Read analysis.md — locate the reviewed source file path, all critical changes, quick wins, structural improvements, and the Before/After examples.

1. Apply every recommended change in this order:

• Critical fixes first (NPE chains → Optional, double → BigDecimal, race conditions → ConcurrentHashMap)
• Quick wins (loops → streams, DTOs → Records, grouping → Collectors.groupingBy)
• Structural improvements (virtual threads, sealed classes, pattern matching)
• Modern Java features (var, method references, text blocks)

1. Write the modernized file as Modern.java alongside the original. Never overwrite the original.

1. Apply all financial domain rules without exception:

• BigDecimal for every monetary value — never double or float
• ZonedDateTime for timestamps — never Date
• Compact constructor validation in every Record
• ConcurrentHashMap.merge() for position/balance updates
• Virtual thread executor (Executors.newVirtualThreadPerTaskExecutor())

1. Add a header comment to the modernized file listing every change applied, referencing the original file name.

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Output

After writing the file, report:

Implementation Summary

• Source: .java
• Output: Modern.java
• Changes applied: N

List each change applied, e.g.:

• [x] getCounterpartyBalance — unguarded chain → Optional
• [x] getPendingHighValueTrades — for-loop → stream filter/collect
• [x] calculateNetExposure — double arithmetic → BigDecimal stream reduction
• [x] groupByCounterparty — manual HashMap loop → Collectors.groupingBy
• [x] updatePosition — synchronized HashMap → ConcurrentHashMap.merge()
• [x] executor — fixed thread pool → virtual thread executor
• [x] TradePosition — mutable inner class → Record with compact constructor validation
• [x] Empty catch block — removed, exception propagates to caller

Final Modernization Score

Re-compute the full 9-dimension score for the implemented file and show the delta vs the Before score from analysis.md:

| Dimension | Before | After | |---|---|---| | NPE prevention | X/15 | X/15 | | Monetary precision | X/15 | X/15 | | Thread safety | X/15 | X/15 | | Streams / collections | X/10 | X/10 | | Exception handling | X/10 | X/10 | | Modern data carriers | X/10 | X/10 | | Concurrency model | X/10 | X/10 | | Modern Java features | X/10 | X/10 | | Financial domain rules | X/5 | X/5 | | TOTAL | X/100 | X/100 |

Improvement: +X points

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Rules

• Never modify the original file.
• Never implement without analysis.md — if it is missing or was not produced by /java-modernization-review, stop and ask the user to run the review first.
• If the original file has already been modernized (a *Modern.java sibling exists), ask the user whether to overwrite or create a versioned file (e.g., *Modern2.java).

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: Santoshrt999
• Source: Santoshrt999/Java-Claude-Skills
• License: MIT
• Homepage: https://github.com/Santoshrt999/Java-Claude-Skills

Install and usage instructions live in the source repository linked above.