Add Java Budget Tracker CLI Application by devin-ai-integration[bot] · Pull Request #139 · Cognition-Partner-Workshops/ts-java-spring-boot-realworld

devin-ai-integration · 2026-04-30T08:34:28Z

Summary

Adds a standalone Java command-line budget tracker application in the budget-tracker/ directory. The application supports:

Add income entries with a description and amount
Add expense entries with a category, description, and amount
View summary showing total income, total expenses, and net balance
List all transactions in chronological order with type, category, and amount
Filter by category — displays available categories and shows only matching transactions (case-insensitive)
Separate functions for each operation (clean separation into model, service, storage, and CLI layers)
JSON file persistence via Gson — saves all entries to budget_data.json and reloads on startup
Input validation with clear error messages for empty fields, non-positive amounts, non-numeric input, NaN, and Infinity
Atomic file writes — writes to a temp file first, then atomically renames to prevent data loss on I/O failures

Tech Stack

Java 21 (JDK 21), Gradle 8.7 (with wrapper)
Gson for JSON serialization
JUnit 5 for testing, JaCoCo for coverage (80%+ line coverage gate)
Checkstyle for linting (0 violations)

Project Structure

budget-tracker/
├── build.gradle
├── settings.gradle
├── gradlew / gradlew.bat
├── config/checkstyle/checkstyle.xml
└── src/
    ├── main/java/com/budgettracker/
    │   ├── BudgetTrackerApp.java      # CLI entry point (6 menu options)
    │   ├── model/
    │   │   ├── Transaction.java       # Data model
    │   │   └── TransactionType.java   # INCOME/EXPENSE enum
    │   ├── service/
    │   │   └── BudgetService.java     # Business logic + category filtering
    │   └── storage/
    │       └── StorageService.java    # JSON file persistence (atomic writes)
    └── test/java/com/budgettracker/
        ├── BudgetTrackerAppTest.java
        ├── model/TransactionTest.java
        ├── service/BudgetServiceTest.java
        └── storage/StorageServiceTest.java

Review & Testing Checklist for Human

Run cd budget-tracker && ./gradlew clean check to confirm build, tests, coverage, and lint pass
Run the app: cd budget-tracker && ./gradlew run --console=plain
Test filter feature: add expenses with different categories, then use option 5 to filter
Verify JSON persistence: add entries, exit, re-run, confirm data reloaded
Test invalid inputs: empty descriptions, negative amounts, NaN, Infinity, invalid menu options

Notes

The budget tracker is self-contained in the budget-tracker/ directory and does not affect the existing Spring Boot application
Migrated from Maven/JDK 17 to Gradle 8.7/JDK 21 per user request
All Devin Review findings addressed: NaN/Infinity validation, test teardown lifecycle, null-safe category handling, save failure rollback, atomic file writes, JsonIOException handling

Link to Devin session: https://partner-workshops.devinenterprise.com/sessions/e3d98600bc714620a973acac2a14135e

- Add income entries with description and amount - Add expense entries with category, description, and amount - Display summary with total income, expenses, and net balance - List all transactions in chronological order - Separate functions for each operation - JSON file persistence with reload on startup - Input validation with clear error messages - 95% code coverage with JUnit 5 tests - Checkstyle linting with zero violations

devin-ai-integration · 2026-04-30T08:34:30Z

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- Reject NaN and Infinity in readAmount() with Double.isFinite check - Add @AfterEach to tearDown() in BudgetTrackerAppTest - Fix System.out restoration in BudgetServiceTest with proper @BeforeEach/@AfterEach lifecycle - Add tests for NaN and Infinity rejection

Prevents NullPointerException when Gson deserializes entries with missing category field.

Check storageService.save() return value in addIncome/addExpense. If save fails, remove the transaction from the in-memory list and throw RuntimeException so the CLI shows an error instead of a false success message.

Use consistent space-separated columns with matching widths in both the printTransactions() header and Transaction.toString().

Reject NaN and Infinity at the BudgetService API level, matching the CLI-layer validation for defense in depth.

JsonIOException is a sibling of JsonSyntaxException (both extend JsonParseException), not caught by IOException. Add explicit catch blocks to prevent uncaught crashes during startup and to ensure save() returns false for BudgetService rollback logic.

- Replace Maven pom.xml with Gradle build.gradle targeting Java 21 - Add Gradle wrapper (8.7) for reproducible builds - Add Checkstyle config and JaCoCo coverage verification - Implement atomic save via temp file + Files.move() to prevent data loss on write failures - Update .gitignore for Gradle build artifacts

- New menu option 5: Filter by Category - Shows available categories, accepts user input, displays matching transactions with case-insensitive matching - BudgetService: getCategories(), filterByCategory(), printFilteredTransactions() - BudgetTrackerApp: handleFilterByCategory() with input validation - Comprehensive tests for service and CLI layers - Exit moved to option 6