sync with ch15 revisions

ChrisMayfield · ChrisMayfield · commit de389a06e509 · 2019-10-05T20:19:13.000-04:00
diff --git a/ch15/Cell.java b/ch15/Cell.java
@@ -6,7 +6,7 @@
  */
 public class Cell {
 
-	public static final Color colors[] = {Color.WHITE, Color.BLACK};
+    public static final Color[] COLORS = {Color.WHITE, Color.BLACK};
 
     private final int x;
     private final int y;
@@ -33,8 +33,7 @@ public Cell(int x, int y, int size) {
      * @param g graphics context
      */
     public void draw(Graphics g) {
-    	Color color = colors[this.state];
-        g.setColor(color);
+        g.setColor(COLORS[this.state]);
         g.fillRect(x + 1, y + 1, size - 1, size - 1);
         g.setColor(Color.LIGHT_GRAY);
         g.drawRect(x, y, size, size);
diff --git a/ch15/Conway.java b/ch15/Conway.java
@@ -13,14 +13,14 @@ public class Conway extends Automaton {
      */
     public Conway() {
         grid = new GridCanvas(30, 25, SIZE);
-        grid.turnCellOn(1, 2);
-        grid.turnCellOn(2, 2);
-        grid.turnCellOn(3, 2);
-        grid.turnCellOn(6, 1);
-        grid.turnCellOn(7, 2);
-        grid.turnCellOn(7, 3);
-        grid.turnCellOn(8, 1);
-        grid.turnCellOn(8, 2);
+        grid.turnOn(1, 2);
+        grid.turnOn(2, 2);
+        grid.turnOn(3, 2);
+        grid.turnOn(6, 1);
+        grid.turnOn(7, 2);
+        grid.turnOn(7, 3);
+        grid.turnOn(8, 1);
+        grid.turnOn(8, 2);
     }
 
     /**
@@ -71,7 +71,7 @@ public Conway(String path, int margin) {
             for (int c = 0; c < line.length(); c++) {
                 char x = line.charAt(c);
                 if (x == 'O') {
-                	grid.getCell(r + margin, c + margin).turnOn();
+                    grid.turnOn(r + margin, c + margin);
                 }
             }
         }
@@ -122,21 +122,32 @@ private static void updateCell(Cell cell, int count) {
     }
 
     /**
-     * Simulates one round of Conway's Game of Life.
+     * Counts the neighbors before changing anything.
+     * 
+     * @return number of neighbors for each cell
      */
-    public void update() {
+    private int[][] countNeighbors() {
         int rows = grid.numRows();
         int cols = grid.numCols();
 
-        // count neighbors before changing anything
         int[][] counts = new int[rows][cols];
         for (int r = 0; r < rows; r++) {
             for (int c = 0; c < cols; c++) {
                 counts[r][c] = countAlive(r, c);
             }
         }
+        return counts;
+    }
+
+    /**
+     * Updates each cell based on neighbor counts.
+     * 
+     * @param counts number of neighbors for each cell
+     */
+    private void updateGrid(int[][] counts) {
+        int rows = grid.numRows();
+        int cols = grid.numCols();
 
-        // update each cell based on neighbor counts
         for (int r = 0; r < rows; r++) {
             for (int c = 0; c < cols; c++) {
                 Cell cell = grid.getCell(r, c);
@@ -145,6 +156,14 @@ public void update() {
         }
     }
 
+    /**
+     * Simulates one round of Conway's Game of Life.
+     */
+    public void update() {
+        int[][] counts = countNeighbors();
+        updateGrid(counts);
+    }
+
     /**
      * Creates and runs the simulation.
      * 
diff --git a/ch15/GridCanvas.java b/ch15/GridCanvas.java
@@ -61,7 +61,7 @@ public Cell getCell(int r, int c) {
      * @param r row index
      * @param c column index
      */
-    public void turnCellOn(int r, int c) {
+    public void turnOn(int r, int c) {
         array[r][c].turnOn();
     }
 
diff --git a/ch15/Langton.java b/ch15/Langton.java
@@ -21,10 +21,9 @@ public Langton(int rows, int cols) {
     }
 
     /**
-     * Simulates one round of Langton's Ant.
+     * Flip the color of the current cell.
      */
-    public void update() {
-
+    private void flipCell() {
         Cell cell = grid.getCell(xpos, ypos);
         if (cell.isOff()) {
             // at a white square; turn right and flip color
@@ -35,8 +34,12 @@ public void update() {
             head = (head + 3) % 4;
             cell.turnOff();
         }
+    }
 
-        // move forward one unit
+    /**
+     * Move the ant forward one unit.
+     */
+    private void moveAnt() {
         if (head == 0) {
             ypos -= 1;
         } else if (head == 1) {
@@ -46,8 +49,14 @@ public void update() {
         } else {
             xpos -= 1;
         }
+    }
 
-        // TODO: draw a triangle to show the ant
+    /**
+     * Simulates one round of Langton's Ant.
+     */
+    public void update() {
+        flipCell();
+        moveAnt();
     }
 
     /**

Original file line number	Diff line number	Diff line change
`@@ -61,7 +61,7 @@ public Cell getCell(int r, int c) {`
`61`	`61`	`* @param r row index`
`62`	`62`	`* @param c column index`
`63`	`63`	`*/`
`64`		`- public void turnCellOn(int r, int c) {`
	`64`	`+ public void turnOn(int r, int c) {`
`65`	`65`	`array[r][c].turnOn();`
`66`	`66`	`}`
`67`	`67`