added RegularPolygon

ChrisMayfield · ChrisMayfield · commit 40f4366be047 · 2019-08-31T16:33:50.000-04:00
diff --git a/ch15/Actor.java b/ch15/Actor.java
@@ -11,7 +11,7 @@ public interface Actor {
     void act();
 
     /**
-     * Paints the simulation element in the context.
+     * Draws the simulation element in the context.
      * 
      * @param g graphics context
      */
diff --git a/ch15/RegularPolygon.java b/ch15/RegularPolygon.java
@@ -0,0 +1,80 @@
+import java.awt.Graphics;
+import java.awt.Polygon;
+
+/**
+ * A polygon that is equiangular (all angles are equal in measure) and
+ * equilateral (all sides have the same length).
+ */
+public class RegularPolygon extends Polygon implements Actor {
+
+    public static final String[] NAMES = {null, null, null,
+            "Triangle", "Square", "Pentagon", "Hexagon",
+            "Heptagon", "Octagon", "Nonagon", "Decagon"};
+
+    /**
+     * Constructs a regular polygon.
+     * 
+     * @param nsides the number of sides
+     * @param length length of each side
+     */
+    public RegularPolygon(int nsides, int length) {
+
+        // validate and store arguments
+        if (nsides < 3 || nsides >= NAMES.length) {
+            throw new IllegalArgumentException("invalid nsides");
+        }
+        if (length < 1) {
+            throw new IllegalArgumentException("invalid length");
+        }
+
+        // initialize Polygon attributes
+        npoints = nsides;
+        xpoints = new int[nsides];
+        ypoints = new int[nsides];
+
+        // compute the radius, angle between vertexes, and rotation
+        double radius = length / (2.0 * Math.sin(Math.PI / nsides));
+        double angle = 2.0 * Math.PI / nsides;
+        double rotate = Math.PI / nsides + Math.PI / 2.0;
+
+        // 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));
+        }
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder str = new StringBuilder();
+        str.append(NAMES[npoints]);
+        str.append('[');
+        for (int i = 0; i < npoints; i++) {
+            if (i > 0) {
+                str.append(", ");
+            }
+            // append the next (x, y) point
+            str.append('(');
+            str.append(xpoints[i]);
+            str.append(", ");
+            str.append(ypoints[i]);
+            str.append(')');
+        }
+        str.append(']');
+        return str.toString();
+    }
+
+    @Override
+    public void act() {
+        // nothing to do
+    }
+
+    @Override
+    public void draw(Graphics g) {
+        System.out.println(this);
+        g.drawPolygon(this);
+    }
+
+}
diff --git a/ch15/Sim1.java b/ch15/Sim1.java
@@ -0,0 +1,39 @@
+import javax.swing.JFrame;
+
+/**
+ * Example simulation of stationary objects.
+ */
+public class Sim1 {
+
+    /**
+     * Test program that draws a few polygons.
+     * 
+     * @param args command-line arguments
+     */
+    public static void main(String[] args) {
+
+        // create some regular polygons
+        RegularPolygon p3 = new RegularPolygon(3, 100);
+        RegularPolygon p4 = new RegularPolygon(4, 100);
+        RegularPolygon p5 = new RegularPolygon(5, 100);
+
+        // move them out of the corner
+        p3.translate(100, 100);
+        p4.translate(250, 250);
+        p5.translate(400, 400);
+
+        // add polygons to a drawing
+        Drawing drawing = new Drawing(800, 600);
+        drawing.add(p3);
+        drawing.add(p4);
+        drawing.add(p5);
+
+        // set up the window frame
+        JFrame frame = new JFrame("Drawing");
+        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        frame.add(drawing);
+        frame.pack();
+        frame.setVisible(true);
+    }
+
+}
diff --git a/ch15/Sim2.java b/ch15/Sim2.java
@@ -1,9 +1,9 @@
 import javax.swing.JFrame;
 
 /**
- * Example simulation of moving objects.
+ * Example simulation of rotating objects.
  */
-public class Main {
+public class Sim2 {
 
     /**
      * Sets up the drawing, creates the actors, and runs the simulation.

Original file line number	Diff line number	Diff line change
`@@ -11,7 +11,7 @@ public interface Actor {`
`11`	`11`	`void act();`
`12`	`12`
`13`	`13`	`/**`
`14`		`- * Paints the simulation element in the context.`
	`14`	`+ * Draws the simulation element in the context.`
`15`	`15`	`*`
`16`	`16`	`* @param g graphics context`
`17`	`17`	`*/`