Suggesting changes

AllenDowney · AllenDowney · commit dbcdbc82f3ba · 2019-09-14T15:12:30.000-04:00
diff --git a/ch16/BlinkingPolygon.java b/ch16/BlinkingPolygon.java
@@ -1,11 +1,12 @@
 import java.awt.Color;
+import java.awt.Graphics;
 
 /**
  * A polygon that periodically changes colors on/off.
  */
 public class BlinkingPolygon extends RegularPolygon {
 
-    private Color onColor;
+    private boolean drawFlag;
     private int count;
 
     /**
@@ -17,23 +18,24 @@ public class BlinkingPolygon extends RegularPolygon {
      */
     public BlinkingPolygon(int nsides, int radius, Color color) {
         super(nsides, radius, color);
-        onColor = color;
+        drawFlag = true;
         count = 0;
     }
-
+    
     @Override
     public void step() {
-        // count to ten first
+        // every 10 steps toggle drawFlag
         count++;
-        if (count >= 10) {
+        if (count == 10) {
             count = 0;
-            // toggle the color
-            if (color != onColor) {
-                color = onColor;
-            } else {
-                color = Color.WHITE;
-            }
+            drawFlag = !drawFlag;
         }
     }
-
+    
+    @Override
+    public void draw(Graphics g) {
+    	if (drawFlag) {
+    		super.draw(g);
+    	}
+    }
 }
diff --git a/ch16/MovingPolygon.java b/ch16/MovingPolygon.java
@@ -52,5 +52,4 @@ public void step() {
         // move one step
         translate(dx, dy);
     }
-
 }
diff --git a/ch16/RegularPolygon.java b/ch16/RegularPolygon.java
@@ -20,7 +20,7 @@ public class RegularPolygon extends Polygon implements Actor {
      * @param nsides the number of sides
      */
     public RegularPolygon(int nsides) {
-        this(nsides, 100);
+        this(nsides, 6);
     }
 
     /**
@@ -47,7 +47,7 @@ public RegularPolygon(int nsides, int radius, Color color) {
         if (nsides < 3) {
             throw new IllegalArgumentException("invalid nsides");
         }
-        if (radius < 1) {
+        if (radius <= 0) {
             throw new IllegalArgumentException("invalid radius");
         }
         if (color == null) {
@@ -68,10 +68,10 @@ public RegularPolygon(int nsides, int radius, Color color) {
 
         // compute x and y coordinates, centered around the origin
         for (int i = 0; i < nsides; i++) {
-            xpoints[i] = (int) Math.round(
-                    radius * Math.cos(i * angle + rotate));
-            ypoints[i] = (int) Math.round(
-                    radius * Math.sin(i * angle + rotate));
+            double x = radius * Math.cos(i * angle + rotate);
+			xpoints[i] = (int) Math.round(x);
+            double y = radius * Math.sin(i * angle + rotate);
+			ypoints[i] = (int) Math.round(y);
         }
     }
 
@@ -110,5 +110,4 @@ public String toString() {
         str.append(']');
         return str.toString();
     }
-
 }
diff --git a/ch16/Sim1.java b/ch16/Sim1.java
@@ -37,5 +37,4 @@ public static void main(String[] args) {
         frame.pack();
         frame.setVisible(true);
     }
-
 }
diff --git a/ch16/Sim2.java b/ch16/Sim2.java
@@ -54,5 +54,4 @@ public static void main(String[] args) {
             }
         }
     }
-
 }
diff --git a/ch16/Sim3.java b/ch16/Sim3.java
@@ -43,6 +43,12 @@ public Sim3() {
         toolkit = frame.getToolkit();
     }
 
+    @Override
+    public void actionPerformed(ActionEvent e) {
+        toolkit.sync();
+        drawing.step();
+    }
+    
     /**
      * Create and start the timer.
      *
@@ -53,11 +59,4 @@ public static void main(String[] args) {
         Timer timer = new Timer(1000 / 30, sim);
         timer.start();
     }
-
-    @Override
-    public void actionPerformed(ActionEvent e) {
-        toolkit.sync();
-        drawing.step();
-    }
-
 }
diff --git a/ch16/WhackAMole.java b/ch16/WhackAMole.java
@@ -5,7 +5,7 @@
 import javax.swing.Timer;
 
 /**
- * Simulates the arcade game of Whack-A-Mole.
+ * Simulates the arcade game Whack-A-Mole.
  * https://en.wikipedia.org/wiki/Whac-A-Mole
  */
 public class WhackAMole implements ActionListener {
@@ -37,21 +37,22 @@ public WhackAMole() {
         toolkit = frame.getToolkit();
     }
 
+    @Override
+    public void actionPerformed(ActionEvent e) {
+        toolkit.sync();
+        drawing.step();
+    }
+    
     /**
      * Create and start the timer.
      *
      * @param args command-line arguments
      */
     public static void main(String[] args) {
         WhackAMole sim = new WhackAMole();
+        
+        // TODO: Can we explain the 1000 / 30 or write it so it's obvious?
         Timer timer = new Timer(1000 / 30, sim);
         timer.start();
     }
-
-    @Override
-    public void actionPerformed(ActionEvent e) {
-        toolkit.sync();
-        drawing.step();
-    }
-
 }

Original file line number	Diff line number	Diff line change
`@@ -52,5 +52,4 @@ public void step() {`
`52`	`52`	`// move one step`
`53`	`53`	`translate(dx, dy);`
`54`	`54`	`}`
`55`		`-`
`56`	`55`	`}`
Original file line number	Diff line number	Diff line change
`@@ -20,7 +20,7 @@ public class RegularPolygon extends Polygon implements Actor {`
`20`	`20`	`* @param nsides the number of sides`
`21`	`21`	`*/`
`22`	`22`	`public RegularPolygon(int nsides) {`
`23`		`- this(nsides, 100);`
	`23`	`+ this(nsides, 6);`
`24`	`24`	`}`
`25`	`25`
`26`	`26`	`/**`
`@@ -47,7 +47,7 @@ public RegularPolygon(int nsides, int radius, Color color) {`
`47`	`47`	`if (nsides < 3) {`
`48`	`48`	`throw new IllegalArgumentException("invalid nsides");`
`49`	`49`	`}`
`50`		`- if (radius < 1) {`
	`50`	`+ if (radius <= 0) {`
`51`	`51`	`throw new IllegalArgumentException("invalid radius");`
`52`	`52`	`}`
`53`	`53`	`if (color == null) {`
`@@ -68,10 +68,10 @@ public RegularPolygon(int nsides, int radius, Color color) {`
`68`	`68`
`69`	`69`	`// compute x and y coordinates, centered around the origin`
`70`	`70`	`for (int i = 0; i < nsides; i++) {`
`71`		`- xpoints[i] = (int) Math.round(`
`72`		`- radius * Math.cos(i * angle + rotate));`
`73`		`- ypoints[i] = (int) Math.round(`
`74`		`- radius * Math.sin(i * angle + rotate));`
	`71`	`+ double x = radius * Math.cos(i * angle + rotate);`
	`72`	`+ xpoints[i] = (int) Math.round(x);`
	`73`	`+ double y = radius * Math.sin(i * angle + rotate);`
	`74`	`+ ypoints[i] = (int) Math.round(y);`
`75`	`75`	`}`
`76`	`76`	`}`
`77`	`77`
`@@ -110,5 +110,4 @@ public String toString() {`
`110`	`110`	`str.append(']');`
`111`	`111`	`return str.toString();`
`112`	`112`	`}`
`113`		`-`
`114`	`113`	`}`
Original file line number	Diff line number	Diff line change
`@@ -37,5 +37,4 @@ public static void main(String[] args) {`
`37`	`37`	`frame.pack();`
`38`	`38`	`frame.setVisible(true);`
`39`	`39`	`}`
`40`		`-`
`41`	`40`	`}`
Original file line number	Diff line number	Diff line change
`@@ -54,5 +54,4 @@ public static void main(String[] args) {`
`54`	`54`	`}`
`55`	`55`	`}`
`56`	`56`	`}`
`57`		`-`
`58`	`57`	`}`
Original file line number	Diff line number	Diff line change
`@@ -43,6 +43,12 @@ public Sim3() {`
`43`	`43`	`toolkit = frame.getToolkit();`
`44`	`44`	`}`
`45`	`45`
	`46`	`+ @Override`
	`47`	`+ public void actionPerformed(ActionEvent e) {`
	`48`	`+ toolkit.sync();`
	`49`	`+ drawing.step();`
	`50`	`+ }`
	`51`	`+`
`46`	`52`	`/**`
`47`	`53`	`* Create and start the timer.`
`48`	`54`	`*`
`@@ -53,11 +59,4 @@ public static void main(String[] args) {`
`53`	`59`	`Timer timer = new Timer(1000 / 30, sim);`
`54`	`60`	`timer.start();`
`55`	`61`	`}`
`56`		`-`
`57`		`- @Override`
`58`		`- public void actionPerformed(ActionEvent e) {`
`59`		`- toolkit.sync();`
`60`		`- drawing.step();`
`61`		`- }`
`62`		`-`
`63`	`62`	`}`