CS1 Standard Demo Page

/*
 *A program to paint, centered on the canvas, a circle of randomly colored, spaced, dots.
 */
package npw;
import painter.SPainter;
import shapes.SCircle;
import javax.swing.*;
import java.awt.*;
import java.util.Random;
import java.util.Scanner;


public class SimpleDots {
    private void paintTheImage() {
        //Get the input information
        int radius = getNumber("circle radius");
        int smallRadius = getNumber("small circle radius");
        String color = JOptionPane.showInputDialog("color");

        //Establish the painter
        SPainter painter = new SPainter("Simple Dots", radius*2 + 50, radius*2 + 50);
        painter.setBrushWidth(3);
        SCircle circle = new SCircle(radius);
        SCircle dot  = new SCircle(smallRadius);

        if (color.equalsIgnoreCase("red")){
            painter.setColor(Color.red);
        } else if (color.equalsIgnoreCase("green")){
            painter.setColor(Color.green);
        }else if (color.equalsIgnoreCase("blue")){
            painter.setColor(Color.blue);
        }else if (color.equalsIgnoreCase("random")){
            painter.setColor(Color.BLACK);
        }
        //Paint the squares
        paintSimpleDots(painter, circle, dot);
    }

    private void paintSimpleDots(SPainter painter, SCircle circle, SCircle dot) {
        //Position the painter to begin drawing the rows
        painter.mfd(circle.radius());
        painter.tr();
        //Paint the circle of squares
        double moved = 0;
        while (moved < circle.diameter()) {
            double chord = chordLength(circle.radius() - moved, circle);
            int dots = dotsOnLineCount(chord, dot.diameter());
            paintRow(painter, dot, dots);
            nextRow(painter, dot.diameter());
            moved = moved + dot.diameter();
        }
        //Make the method invariant with respect to painter position
        painter.tl();
        painter.mfd(circle.radius());
    }
    //Move to the next row
    private void nextRow(SPainter painter, double rowHeight){
        painter.tr();
        painter.mfd(rowHeight);
        painter.tl();
    }
    //Assumes the painter is at the center of the row to paint, facing right.
    private void paintRow(SPainter painter, SCircle dot, int dotsToPaint){
        //Move backward 1/2 of the length we're painting to get ready to paint the row
        double centerOffset = ((dotsToPaint * dot.diameter()) / 2) - dot.diameter()/2;
        painter.mbk(centerOffset);

        //Paint the row of squares.
        int painted = 0;
        while ( painted < dotsToPaint){
            paintOneSquare(painter, dot);
            painter.mfd(dot.diameter());
            painted = painted + 1;
        }
        //Make the method invariant with respect to painter position.
        painter.mbk(centerOffset + dot.diameter());
    }

    private void paintOneSquare(SPainter painter, SCircle dot) {
        dot.s2();
        painter.paint(dot);
        dot.x2();
    }
    private static int dotsOnLineCount(double lineLength, double sideLength){
        int dots = ((int)Math.ceil((lineLength - sideLength) / sideLength) + 1);
        return dots;
    }
    private double chordLength(double yOffset, SCircle circle){
        double xLength = Math.sqrt(Math.pow(circle.radius(), 2) - Math.pow(yOffset, 2));
        double chordLength = xLength * 2;
        return chordLength;
    }
    private static int getNumber(String prompt) {
        String nss = JOptionPane.showInputDialog(null, prompt+"?");
        Scanner scanner = new Scanner(nss);
        return scanner.nextInt();
    }
    private static Color randomColor() {
        Random rgen = new Random();
        int r = rgen.nextInt(256);
        int g = rgen.nextInt(256);
        int b = rgen.nextInt(256);
        return new Color(r,g,b);
    }
    public SimpleDots(){
        paintTheImage();
    }
    public static void main(String[] args){
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new SimpleDots();
            }
        });
    }

}