documentation and formatting to 80 character width.

src/App.java

@@ -8,7 +8,8 @@ import java.awt.BorderLayout;
 import java.awt.Dimension;
 
 /**
- * Runner class for the Sudoku App, managing the GUI and coordinating internal logic.
+ * Runner class for the Sudoku App, managing the GUI and coordinating 
+ * internal logic.
  */
 public class App extends JFrame {
     // GUI fields
@@ -33,7 +34,8 @@ public class App extends JFrame {
      * Basic JFrame settings and setup for the GUI.
      */
     private void initSetup() {
-        // TODO: These are just some default values, these should use the values from Settings.
+        // TODO: These are just some default values, these should use the 
+        //       values from Settings.
         setDefaultCloseOperation(EXIT_ON_CLOSE);
         setLayout(new BorderLayout());
         setPreferredSize(new Dimension(750, 550));
@@ -42,9 +44,13 @@ public class App extends JFrame {
         setLocationRelativeTo(null);
 
         try {
-            UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
+            UIManager.setLookAndFeel(
+                UIManager.getCrossPlatformLookAndFeelClassName()
+            );
         } catch (Exception e) {
-            System.out.println("Error with cross platform look/feel in frameSetup().");
+            System.out.println(
+                "Error with cross platform look/feel in frameSetup()."
+            );
         }
     }
 
@@ -76,9 +82,10 @@ public class App extends JFrame {
     public static void main(String[] args) {
         if(args.length == 0)
             new App().setVisible(true);
-        else if(args[0].equals("-c") || args[0].equals("--cli"))
+        else if(args[0].equals("-c") ||
+                args[0].equals("--cli"))
             cli();
         else
             new App().setVisible(true);
     }
-}
+}

src/Nav.java

@@ -33,7 +33,7 @@ public class Nav extends JPanel {
      * Create a new Nav in a command-line interface. This is intended for
      * debugging rather than practical use.
      *
-     * Additionally, even for debugging, this should be used since default
+     * Additionally, even for debugging, this should not be used since default
      * file I/O behavior is dictated by the values in the Settings object.
      */
     public Nav() {
@@ -61,6 +61,8 @@ public class Nav extends JPanel {
         super();
         this.s = s;
         
+        // If the program is being run in the command-line, prompt the user
+        // for the name of the input file.
         if(cli) {
             System.out.println("Welcome to the Sudoku Solver!");
 
@@ -73,10 +75,10 @@ public class Nav extends JPanel {
             in.close();
 
             openFile(inputFilename);
-        } else {
+
-            // TODO: Create the GUI for the Nav bar.
+        // Otherwise, create the GUI for the Nav bar.
-            createGUI();
+        } else createGUI();
-        }
+            
     }
 
     /**
@@ -92,6 +94,8 @@ public class Nav extends JPanel {
         JButton solve = new JButton("Solve");
             solve.setFont(s.getFont()); // TODO: Make custom Button class.
 
+        // Add the ComboBox for the file options, the elapsed time label, and
+        // the solve button to the Nav Panel.
         add(createFileOptions());
         add(elapsedTime);
         add(solve);
@@ -103,12 +107,14 @@ public class Nav extends JPanel {
      * @return ComboBox<String>
      */
     private ComboBox<String> createFileOptions() {
+        // Create a new ComboBox with the default styling.
         ComboBox<String> fileOptions = new ComboBox<>(s);
             fileOptions.addItem("New");
             fileOptions.addItem("Open");
             fileOptions.addItem("Save");
             fileOptions.addItem("Exit");
 
+        // Add an ActionListener to the ComboBox to handle the user's selection.
         fileOptions.addActionListener(e -> {
             String selected = (String) fileOptions.getSelectedItem();
             switch(selected) {
@@ -154,19 +160,19 @@ public class Nav extends JPanel {
      * Open an existing .sdku file in the user's file system, using a GUI.
      */
     private void openFile() {
+        // No error handling is needed here, since the Settings class ensures
+        // that the default directory is always a valid directory.
         File defaultDirectory = new File(s.getDefaultDirectory());
-        if(defaultDirectory != null || !defaultDirectory.isDirectory()) {
-            defaultDirectory.mkdirs();
-        }
 
-        FileChooser fc = new FileChooser(defaultDirectory);
+        // Custom FileChooser class for style and to ensure the user can only
+        // select .sdku files.
+        FileChooser fc = new FileChooser(defaultDirectory, s);
         int result = fc.showOpenDialog(this);
 
+        // If the user selects a file, open it.
         if(result == FileChooser.APPROVE_OPTION) {
             f = fc.getSelectedFile();
             createGrid(f);
-        } else {
-            System.out.println("No file was selected.");
         }
     }
 
@@ -179,6 +185,7 @@ public class Nav extends JPanel {
      */
     private void openFile(String filename) {
         File f = new File("resources/" + filename + ".sdku");
+        // If the file does not exist, print an error message and return.
         if(f == null || !f.exists() || f.isDirectory() || !f.canRead()) {
             System.out.println(
                     "The file " + filename + 
@@ -192,6 +199,7 @@ public class Nav extends JPanel {
             return;
         }
 
+        // Otherwise, open the file and populate the grid.
         System.out.println("Opening the file " + filename + ".sdku.");
         createGrid(f);
     }
@@ -241,21 +249,31 @@ public class Nav extends JPanel {
      */
     private void createGrid(File f) {
         try (Scanner in = new Scanner(f)) {
+            // Create a new 9x9 grid of Cells.
             Cell[][] grid = new Cell[9][9];
+            
+            // Read in the file line by line.
             for(int i = 0; i < 9; i++) {
+
+                // Read in the line and create a new Cell for each character.
                 String line = in.nextLine();
                 for(int j = 0; j < 9; j++) {
+
+                    // If the character is a period, the cell is empty.
                     if(line.charAt(j) == '.') {
                         grid[i][j] = new Cell(i, j, 0);
                         continue;
                     }
                     
+                    // Otherwise, the character is a digit.
                     int value = Character.getNumericValue(line.charAt(j));
                     grid[i][j] = new Cell(i, j, value);
                 }
             }
 
             this.grid = grid;
+
+        // If the file is not found, print an error message and return.
         } catch (FileNotFoundException e) {
             String filename = f.getName();
             System.err.println("An error occurred while reading the file " +

src/SudokuChecker.java

@@ -1,35 +1,40 @@
-import java.io.File;
-import java.io.FileNotFoundException;
 import java.util.ArrayList;
-import java.util.Scanner;
-
 
 /**
- * The SudokuChecker class is responsible for checking the validity of a given Sudoku puzzle solution.
+ * The SudokuChecker class is responsible for calculating the solution to
+ * a given Sudoku puzzle.
  * 
- * The SudokuChecker class is also responsible for solving a given Sudoku puzzle.
+ * TODO: The Sudoku algorithm used is efficient and effective for solving
+ * easy and medium puzzles, but it is not optimized for hard puzzles. It
+ * is recommended to use a different algorithm for hard puzzles, likely
+ * a tree & back-track approach.
  */
 public class SudokuChecker {
     private Cell[][] grid;
     
     /**
-     * Create a new SudokuChecker object, initializing the grid to the given 9x9 grid of numbers.
+     * Create a new SudokuChecker object, initializing the grid to the given
-     * This should either check each cell as the user inputs a value, or be used to check the validity of a
+     * 9x9 grid of numbers. This should either check each cell as the user 
-     * puzzle when the user requests it.
+     * inputs a value, or be used to check the validity of a puzzle when the 
+     * user requests it.
+     * 
+     * TODO: Currently, this class is not used in the GUI. It is only used in
+     * the command-line interface.
      * 
-     * TODO: Currently, this class is not used in the GUI. It is only used in the command-line interface.
      * @param grid
      */
     public SudokuChecker(Cell[][] grid) {
         this.grid = grid;
         solve();
-        System.out.println("The solution to the Sudoku puzzle is:");
+    }
-        for(int i = 0; i < 9; i++) {
+
-            for(int j = 0; j < 9; j++) {
+    /**
-                System.out.print(grid[i][j].getValue());
+     * Get the solution to the Sudoku puzzle.
-            }
+     * 
-            System.out.println();
+     * @return Cell[][]
-        }
+     */
+    public Cell[][] getSolution() {
+        return grid;
     }
 
     /**
@@ -39,7 +44,10 @@ public class SudokuChecker {
      * @param b
      * @return
      */
-    private ArrayList<Integer> intersection(ArrayList<Integer> a, ArrayList<Integer> b) {
+    private ArrayList<Integer> intersection(
+        ArrayList<Integer> a, 
+        ArrayList<Integer> b
+    ) {
         ArrayList<Integer> intersection = new ArrayList<Integer>();
         for(int i = 0; i < a.size(); i++) {
             if(b.contains(a.get(i))) {
@@ -51,16 +59,25 @@ public class SudokuChecker {
     }
 
      /**
-     * Determine what numbers are available to be placed in the given cell of the grid.
+     * Determine what numbers are available to be placed in the given cell of
-     * This is effectively an intersection of the numbers available in the row, column, and box of the cell.
+     * the grid. This is effectively an intersection of the numbers available
+     * in the row, column, and box of the cell.
      * 
      * @param row
      * @param col
-     * @return an array of numbers that are available to be placed in the given cell
+     * @return an array of numbers that are available to be placed in the 
+     * given cell
      */
     private void getAvailableNumbers(int row, int col) {
-        ArrayList<Integer> intersection = intersection(getRowRemainingNumbers(row), getColRemainingNumbers(col));
+        ArrayList<Integer> intersection = intersection(
-        intersection = intersection(intersection, getBoxRemainingNumbers(row, col));
+            getRowRemainingNumbers(row),
+            getColRemainingNumbers(col)
+        );
+
+        intersection = intersection(
+            intersection,
+            getBoxRemainingNumbers(row, col)
+        );
 
         if(intersection.size() == 0) {
             return;
@@ -77,13 +94,16 @@ public class SudokuChecker {
                 availableNumbers.add(intersection.get(i));
             }
 
-            grid[row][col].setPossibleValues(arrayListToArray(availableNumbers));
+            grid[row][col].setPossibleValues(
+                arrayListToArray(availableNumbers)
+            );
         }
     }   
 
     /**
-     * Update the possible values for cells in the same row, column, and box as the given cell.
+     * Update the possible values for cells in the same row, column, and box
-     * This should always be called once a cell's value has been set, to remove that value from the possible values of other cells.
+     * as the given cell. This should always be called once a cell's value has
+     * been set, to remove that value from the possible values of other cells.
      * 
      * @param row
      * @param col
@@ -112,9 +132,9 @@ public class SudokuChecker {
         int boxCol = col / 3;
         for(int i = 0; i < 3; i++) {
             for(int j = 0; j < 3; j++) {
-                if(grid[boxRow * 3 + i][boxCol * 3 + j].getValue() == 0) {
+                if(grid[boxRow * 3 + i][boxCol * 3 + j].getValue() == 0)
-                    grid[boxRow * 3 + i][boxCol * 3 + j].removePossibleValue(value);
+                    grid[boxRow * 3 + i][boxCol * 3 + j].
-                }
+                        removePossibleValue(value);
             }
         }
     }
@@ -218,7 +238,8 @@ public class SudokuChecker {
     /**
      * Given a list of numbers, return an array of the numbers.
      * 
-     * A helper method to keep the code using arrays instead of lists whenever possible.
+     * A helper method to keep the code using arrays instead of lists 
+     * whenever possible.
      * 
      * @param list
      * @return
@@ -232,9 +253,11 @@ public class SudokuChecker {
     }
 
     /**
-     * Given a 9x9 grid of numbers, return true if the grid is a valid Sudoku puzzle solution, and false otherwise.
+     * Given a 9x9 grid of numbers, return true if the grid is a valid Sudoku
+     * puzzle solution, and false otherwise.
      * 
-     * A valid Sudoku puzzle is one where each row, column, and 3x3 subgrid contains the numbers 1-9 exactly once.
+     * A valid Sudoku puzzle is one where each row, column, and 3x3 subgrid 
+     * contains the numbers 1-9 exactly once.
      * 
      * @return true if the grid is a valid Sudoku puzzle, and false otherwise
      */
@@ -242,10 +265,8 @@ public class SudokuChecker {
         // Check that every cell has a value between 1 and 9.
         for(int i = 0; i < 9; i++) {
             for(int j = 0; j < 9; j++) {
-                if(grid[i][j].getValue() < 1 || grid[i][j].getValue() > 9) {
+                if(grid[i][j].getValue() < 1 || grid[i][j].getValue() > 9)
-                    //System.out.println("Cell at row " + i + " and column " + j + " has an invalid value of " + grid[i][j].getValue() + ".");
                     return false;
-                }
             }
         }
         
@@ -283,7 +304,10 @@ public class SudokuChecker {
                     }
                 }
                 if(!isValidSet(box)) {
-                    System.out.println("Box at row " + i + " and column " + j + " is invalid.");
+                    System.out.println(
+                        "Box at row " + i +
+                        " and column " + j + " is invalid."
+                    );
                     return false;
                 }
             }
@@ -293,10 +317,12 @@ public class SudokuChecker {
     }
     
     /**
-     * Given an array of 9 numbers, return true if the array contains the numbers 1-9 exactly once, and false otherwise.
+     * Given an array of 9 numbers, return true if the array contains the
+     *  numbers 1-9 exactly once, and false otherwise.
      * 
      * @param set an array of 9 numbers
-     * @return true if the array contains the numbers 1-9 exactly once, and false otherwise
+     * @return true if the array contains the numbers 1-9 exactly once, and 
+     * false otherwise
      */
     private boolean isValidSet(int[] set) {
         boolean[] found = new boolean[9];
@@ -311,4 +337,4 @@ public class SudokuChecker {
         }
         return true;
     }
-}
+}

src/gui/FileChooser.java

@@ -11,22 +11,6 @@ import javax.swing.JFileChooser;
 public class FileChooser extends JFileChooser {
     private Settings s;
     
-    /**
-     * Create a new FileChooser with the default directory set to the user's
-     * Sudoku directory and no special styling.
-     * 
-     * @param defaultDirectory
-     */
-    public FileChooser(File defaultDirectory) {
-        super(defaultDirectory);
-        for (File f: defaultDirectory.listFiles()) {
-            ensureFileIsVisible(f);
-        }
-
-        style();
-        setupSettings();
-    }
-    
     /**
      * Create a new FileChooser with the default directory set to the user's
      * Sudoku directory.
@@ -70,7 +54,8 @@ public class FileChooser extends JFileChooser {
         public boolean accept(File f) {
             String name = f.getName().toLowerCase();
             if(name.length() > 5) {
-                return name.substring(name.length() - 5).equals(".sdku") || !f.isDirectory();
+                return name.substring(name.length() - 5).equals(".sdku")
+                    || !f.isDirectory();
             }
             return false;
         }
@@ -79,4 +64,4 @@ public class FileChooser extends JFileChooser {
             return "Sudoku Puzzle Files (*.sdku)";
         }
     }
-}
+}

src/gui/Settings.java

@@ -1,6 +1,5 @@
 package gui;
 
-import java.util.Scanner;
 import java.io.File;
 import java.io.IOException;
 
@@ -12,13 +11,30 @@ import java.awt.FontFormatException;
  * A class solely to store user settings relating to default behaviors,
  * difficulty, filepaths, and more.
  *
- * These user settings are stored in a {TBD} file located at {TBD}.
+ * These user settings are stored in a settings file that must be stored
+ * either in "~/.config/sudoku/settings.json" or 
+ * "%APPDATA%/Local/Sudoku/settings.json" depending on the user's operating
+ * system.
+ * 
+ * (Currently) Configurable settings include:
+ *      - Default Directory
+ *      - New File Properties
+ *      - Font
+ * 
  */
 public class Settings {
     private final String os;
 
+    // The directory where the settings file is located.
+    private String appDirectory; 
+
+    // The default directory for .sdku files.
+    private String defaultDirectory; 
+
+    // The properties for creating a new .sdku file.
     private int newFileProperties;
-    private String defaultDirectory;
+
+    // The font to be used throughout the application.
     private Font font;
 
     /**
@@ -33,11 +49,13 @@ public class Settings {
     public Settings() {
         os = System.getProperty("os.name").toLowerCase();
         if(os.startsWith("windows"))
-            defaultDirectory = System.getProperty("user.home") + "\\AppData\\Local\\Sudoku\\";
+            appDirectory = System.getProperty("user.home") + 
+                            "\\AppData\\Local\\Sudoku\\";
         else
-            defaultDirectory = System.getProperty("user.home") + "/.config/sudoku/";
+            appDirectory = System.getProperty("user.home") + 
+                            "/.config/sudoku/";
 
-        File dir = new File(defaultDirectory);
+        File dir = new File(appDirectory);
         if (!dir.exists() || !dir.isDirectory()) {
             dir.mkdirs();
 
@@ -46,6 +64,31 @@ public class Settings {
         readSettings();
     }
 
+    /**
+     * The Default Directory is a configurable setting, where the user can
+     * specify a default directory to store .sdku files. This is useful for
+     * eliminating the need for user input for file operations.
+     *
+     * By default, the default directory is either "~/.config/sudoku/puzzles"
+     * or "%APPDATA%/Local/Sudoku/Puzzles", depending on the user's operating
+     * system.
+     * 
+     * @return String
+     */
+    public String getDefaultDirectory() {
+        return defaultDirectory;
+    }
+
+    /**
+     * Set the default directory and write it to the settings file.
+     * 
+     * @param defaultDirectory
+     */
+    public void setDefaultDirectory(String defaultDirectory) {
+        this.defaultDirectory = defaultDirectory;
+        updateSettingsFile();
+    }
+
     /**
      * New File Properties is a configurable setting, where the following
      * values are allowable:
@@ -69,32 +112,6 @@ public class Settings {
         updateSettingsFile();
     }
 
-    /**
-     * The Default Directory is a configurable setting, where the user can
-     * specify a default directory to store .sdku files. This is useful for
-     * eliminating the need for user input for file operations.
-     *
-     * NOTE: This does not change the location that the settings file may
-     * be located in. At this time, the settings file is always located in
-     * either "~/.config/sudoku/" or "%APPDATA%/Local/Sudoku/", depending
-     * on the user's operating system.
-     * 
-     * @return String
-     */
-    public String getDefaultDirectory() {
-        return defaultDirectory;
-    }
-
-    /**
-     * Set the default directory and write it to the settings file.
-     * 
-     * @param defaultDirectory
-     */
-    public void setDefaultDirectory(String defaultDirectory) {
-        this.defaultDirectory = defaultDirectory;
-        updateSettingsFile();
-    }
-
     /**
      * The Font is a configurable setting, where the user can specify a
      * font to be used throughout the application.
@@ -134,6 +151,7 @@ public class Settings {
      * settings file.
      */
     private void defaultSettings() {
+        defaultDirectory = appDirectory + "puzzles";
         newFileProperties = 0;
 
         // Load the font from the system directory.
@@ -154,8 +172,8 @@ public class Settings {
      * to populate the Settings file.
      */
      private void readSettings() {
-        File settingsFile = new File(defaultDirectory + "/settings");
+        File settingsFile = new File(appDirectory + "/settings.json");
-        if (!settingsFile.exists()) {
+        if (!settingsFile.exists() && !settingsFile.isDirectory()) {
             defaultSettings();
             return;
         }
@@ -172,7 +190,9 @@ public class Settings {
         // Load the font from the system directory.
         String fontFilepath;
         if(os.startsWith("windows"))
-            fontFilepath = System.getProperty("user.home") + "\\AppData\\Local\\Microsoft\\Windows\\Fonts\\" + fontName + ".ttf";
+            fontFilepath = System.getProperty("user.home") + 
+                            "\\AppData\\Local\\Microsoft\\Windows\\Fonts\\" +
+                            fontName + ".ttf";
         else if(os.startsWith("mac"))
             fontFilepath = "/Library/Fonts/" + fontName + ".ttf";
         else
@@ -180,13 +200,20 @@ public class Settings {
 
         // Register the font with the GraphicsEnvironment.
         try {
-            GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
+            GraphicsEnvironment ge = GraphicsEnvironment.
-            ge.registerFont(Font.createFont(Font.TRUETYPE_FONT, new File(fontFilepath)));
+                getLocalGraphicsEnvironment();
+
+            ge.registerFont(Font.createFont(
+                Font.TRUETYPE_FONT,
+                new File(fontFilepath)
+            ));
+
             return 0;
 
         } catch(IOException | FontFormatException e) {
-            System.out.println("Filepath of font not found: " + fontFilepath + " does not exist.");
+            System.out.println("Filepath of font not found: " +
+                                fontFilepath + " does not exist.");
             return 1;
         }
     }
-}
+}