BudgetBuddy: Building a Finance App with Java & Kotlin

AveryDreamer Novice 1h ago Updated Jul 27, 2026 135 views 15 likes 2 min read

Mixing Java and Kotlin in a single Android project is a great way to handle legacy stability while leveraging modern syntax. I recently put this into practice by building BudgetBuddy, a personal finance tracker designed to strip away the bloat found in most commercial budgeting apps.

The core of the app relies on a local database (SQLite/Room) to keep transaction history private and fast. I focused heavily on Material Design to ensure the UI didn't feel like a boilerplate school project, especially with the implementation of a native dark theme.

Key Functionality

  • Transaction Management: Full CRUD for income and expenses with categorized tagging.
  • Budgetary Constraints: Monthly spending limits that track remaining balances in real-time.
  • Savings Progress: A dedicated module to set targets and monitor accumulation.
  • Bill Splitting: A utility to divide shared costs among group members.
  • Instant Search: A filtered view of the transaction ledger for quick auditing.
BudgetBuddy: Building a Finance App with Java & Kotlin

BudgetBuddy: Building a Finance App with Java & Kotlin

The Tech Stack

  • Languages: Java & Kotlin (Interoperability)
  • IDE: Android Studio
  • UI: XML Layouts & Material Design Components
  • Build Tool: Gradle
  • Storage: SQLite / Room Database

Development Hurdles

BudgetBuddy: Building a Finance App with Java & Kotlin

The biggest pain point was optimizing the RecyclerView for the transaction ledger. When the history grows, scrolling can stutter if you aren't careful with view holders and data binding. I also spent a significant amount of time refining the budget calculation logic to ensure that updates to expenses reflected instantly across the dashboard without triggering redundant database queries.

Deployment & Source

If you want to dive into the implementation or test the build, the project is open source.

BudgetBuddy: Building a Finance App with Java & Kotlin

Source Code: https://github.com/Toxiclikith/budgetBuddy-apk
Direct APK: https://raw.githubusercontent.com/Toxiclikith/budgetBuddy-apk/main/downloads/release/budget-buddy.apk

For the next iteration, I'm planning a deep dive into spending analytics using MPAndroidChart to visualize monthly trends, as raw lists only tell half the story.

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All Replies (3)

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Leo37 Novice 9h ago
used both in a project last year, kotlin's extension functions save so much boilerplate code.
0 Reply
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PatFounder Advanced 9h ago
Did you run into any weird issues with nullability when calling Kotlin from your Java classes?
0 Reply
M
MaxOwl Intermediate 9h ago
did this for a side project once; mixing them actually works surprisingly well in Android Studio.
0 Reply

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