1    /* 
2    This program displays a circle of dots 
3     */
4    package npw;
5    
6    import painter.SPainter;
7    import shapes.SCircle;
8    import shapes.SSquare;
9    
10   import javax.swing.*;
11   import java.awt.*;
12   import java.util.Random;
13   import java.util.Scanner;
14   
15   public class HirstDots{
16   
17       private void paintTheImage(){
18           // Get the input information
19           int radius = getNumber("circle radius");
20           int radius1 = getNumber("dot radius length");
21   
22           // Establish the painter
23           SPainter painter = new SPainter("HirstDots", radius*2+50, radius*2+50);
24           painter.setBrushWidth(3);
25           SCircle circle = new SCircle(radius);
26           SCircle dot = new SCircle(radius1);
27   
28           // Paint the squares
29           paintCircleOfDots(painter, circle, dot);
30       }
31   
32       private void paintCircleOfDots(SPainter painter, SCircle circle, SCircle dot){
33           // Position the painter to begin drawing the rows
34           painter.mfd(circle.radius());
35           painter.tr();
36   
37   
38           // Paint the circle of dots
39           double moved = 0;
40           while (moved < circle.diameter()) {
41               double chord = chordLength(circle.radius() - moved, circle);
42               int dots = DotsOnLineCount(chord, dot.diameter());
43               paintRow(painter, dot, dots);
44               nextRow(painter, dot.diameter());
45               moved = moved + dot.diameter();
46           }
47           // Make the method invariant with respect to painter position
48           painter.tl();
49           painter.mfd(circle.radius());
50   
51       }
52   
53       // Move to the next row
54       private void nextRow(SPainter painter, double rowHeight){
55           painter.tr();
56           painter.mfd(rowHeight);
57           painter.tl();
58   
59   
60       }
61   
62       // Assumes the painter is at the center of the row to paint, facing right.
63       private void paintRow(SPainter painter, SCircle dot, int DotsToPaint){
64           // Move backward 1/2 of the length we're painting to get ready to paint the row.
65           double centerOffset = ( (DotsToPaint * dot.diameter()) / 2) - dot.diameter()/2;
66           painter.mbk(centerOffset);
67   
68   
69           // Paint the row of dots
70           int painted = 0;
71           while (painted < DotsToPaint){
72               paintOneCircle(painter, dot);
73               painter.mfd(dot.diameter());
74               painted = painted + 1;
75   
76           }
77   
78           // Make the method invariant with respect to painter position.
79           painter.mbk(centerOffset + dot.diameter());
80       }
81   
82       private void paintOneCircle(SPainter painter, SCircle dot){
83           dot.shrink(dot.radius() * 0.50);
84           painter.setColor(randomColor());
85           painter.paint(dot);
86           dot.expand(dot.radius()); ///Needed for invariance
87       }
88   
89       private static int DotsOnLineCount(double lineLength, double dotDiameter){
90           int dot = ( (int)Math.ceil( ( lineLength - dotDiameter ) / dotDiameter ) + 1);
91           return dot;
92       }
93   
94       private double chordLength(double yOffset, SCircle circle){
95           double xLength = Math.sqrt(Math.pow(circle.radius(), 2) - Math.pow(yOffset, 2));
96           double chordLength = xLength * 2;
97           return chordLength;
98       }
99   
100      private static int getNumber(String prompt) {
101          String nss = JOptionPane.showInputDialog(null,prompt+"?");
102          Scanner scanner = new Scanner(nss);
103          return scanner.nextInt();
104      }
105  
106      private static Color randomColor() {
107          Random rgen = new Random();
108          int r = rgen.nextInt(256);
109          int g = rgen.nextInt(256);
110          int b = rgen.nextInt(256);
111          return new Color(r,g,b);
112      }
113  
114      public HirstDots() {
115          paintTheImage();
116      }
117  
118      public static void main(String[] args) {
119          SwingUtilities.invokeLater(new Runnable() {
120              public void run() {
121                  new HirstDots();
122              }
123          });
124      }
125  }
126