SudokuApp

An advanced Sudoku game built with vanilla Java and Swing — no frameworks, no external libraries — that lets you generate and play Sudoku puzzles of any size — not just the traditional 9×9 grid.

How it works under the hood

Most Sudoku apps hardcode a fixed 9×9 board. This app takes a different approach — it dynamically builds a valid puzzle for any n×n size you choose.

The process works in three stages:

1. Generate a solved grid — The app first creates a fully valid, completed n×n Sudoku solution using randomised number placement, ensuring every row, column, and sub-box satisfies Sudoku rules.
2. Remove random cells — A calculated number of cells are then cleared from the solved grid, leaving behind the clues (pre-filled numbers) and the blanks the player needs to figure out.
3. Present the puzzle — The resulting board is handed to the player to solve. If they get stuck, the original solution is still stored and can be revealed on request.

This "solve-first, then hide" approach guarantees that every generated puzzle has exactly one valid solution — the one that was computed at the start.

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Features

• Custom grid sizes — Enter any non-prime integer n to generate an n×n Sudoku puzzle
• Randomized puzzle generation — Each game produces a unique board
• Interactive GUI — Built with Java Swing; click number buttons to fill in cells
• Eraser tool — 3 uses per game to clear a filled cell
• Answer checker — Verify your solution with a single click
• Reveal answer — If you're stuck, generate the correct solution after checking

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How to Play

1. Launch the app — a startup window appears asking for your grid size n
2. Enter a non-prime integer (e.g. 4, 6, 9, 16) and click Generate
3. The Sudoku board opens with some cells pre-filled and others blank
4. Use the number buttons at the bottom to select a value, then click an empty cell to fill it
5. Use the ERASER button (up to 3 times) to clear a cell you want to redo
6. When done, click Check to see if your solution is correct
   • ✅ Correct → You win!
   • ❌ Incorrect → Click again to reveal the correct answer
7. Click Close to exit the game window

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Project Structure

sudukoApp/
├── main.java             # Entry point — startup window for choosing grid size
├── UI.java               # Main game window — layout, buttons, game flow
├── Grid.java             # Sudoku grid rendering and cell interaction
├── Box.java              # Manages box/region position indexing
├── Logic.java            # Random number generation for puzzle creation
├── FactorGenerator.java  # Utility for computing grid factors
└── tst.java              # Test/scratch file

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Requirements

• Java JDK 8 or higher
• A Java IDE such as NetBeans (the project was created with NetBeans) or IntelliJ IDEA / Eclipse

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Getting Started

Clone the repository

git clone https://github.com/ks9205124-cloud/sudukoApp.git
cd sudukoApp

Compile

javac -d out *.java

Run

java -cp out suduko.main

Note: The source files belong to the suduko package. Make sure your compilation output directory preserves the package structure.

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Notes

• The grid size must be a non-prime integer (e.g. 4, 6, 8, 9, 10, 12 …). Entering a prime or invalid value will display an error message in the input field.
• Larger grid sizes (e.g. 16×16) are supported but may require resizing the window for comfortable play.

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License

This project currently uses the default NetBeans license template. See individual source files for details.