Question

In Java: How to Program book

a. Draw a square-shaped spiral , centered on the panel, using method drawLine . One technique is to use a loop that increases the line length after drawing every second line. The direction in which to draw the next line should follow a distinct pattern, such as down, left, up, right.

b.Draw a circular spiral using method drawArc to draw one semicircle at a time. Each successive semicircle should have a larger radius (as specified by the bounding rectangle's width) and should continue drawing where the previous semicircle finished.

Answer 1

The answer is in the explanation section below. I hope i have been able to help.

Step-by-step explanation:

package net.eonz.stackoverflow.spiral;

import java.awt.BorderLayout;

import java.awt.Canvas;

import java.awt.Color;

import java.awt.Dimension;

import java.awt.Graphics;

import java.awt.event.MouseEvent;

import java.awt.event.MouseListener;

import java.awt.image.BufferStrategy;

import javax.swing.JFrame;

public class Game extends Canvas implements Runnable, MouseListener

{

private static final long serialVersionUID = 1L;

public static final String NAME = "untitled";

public static final int HEIGHT = 600;

public static final int WIDTH = 600;

public static final int SCALE = 1;

private boolean running = false;

public void start() {

running = true;

new Thread(this).start();

this.addMouseListener(this);

}

public void stop() {

running = false;

}

public void run() {

long last = System.currentTimeMillis();

while (running) {

long now = System.currentTimeMillis();

double dt = (now - last) / 1000.0;

last = now;

update(dt);

render();

}

}

double t = 0;

public void update(double dt) {

t += dt / 16;

if (t > 1)

t = 1;

}

public void render() {

BufferStrategy bs = getBufferStrategy();

if (bs == null) {

createBufferStrategy(3);

return;

}

Graphics g = bs.getDrawGraphics();

g.setColor(Color.white);

g.fillRect(0, 0, this.getWidth(), this.getHeight());

/* SPIRAL MATH IS HERE */

double startingRadius = this.getHeight() * 0.40;

double rotations = 10;

double x = getArmX(startingRadius * (1 - t), t * rotations * Math.PI

* 2);

double y = getArmY(startingRadius * (1 - t), t * rotations * Math.PI

* 2);

g.setColor(Color.black);

g.fillRect((int) (x - 8) + this.getWidth() / 2,

(int) (y - 8) + this.getHeight() / 2, 16, 16);

/* END SPIRAL MATH */

g.dispose();

bs.show();

}

public static double getArmX(double length, double angle) {

return Math.cos(angle) * length;

}

public static double getArmY(double length, double angle) {

return Math.sin(angle) * length;

}

@Override

public void mouseClicked(MouseEvent e) {

this.t = 0;

}

@Override

public void mousePressed(MouseEvent e) {

}

@Override

public void mouseReleased(MouseEvent e) {

}

@Override

public void mouseEntered(MouseEvent e) {

}

@Override

public void mouseExited(MouseEvent e) {

}

public static void main(String[] args) {

Game game = new Game();

game.setMinimumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));

game.setMaximumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));

game.setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));

JFrame frame = new JFrame(Game.NAME);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.setLayout(new BorderLayout());

frame.add(game, BorderLayout.CENTER);

frame.pack();

frame.setLocationRelativeTo(null);

frame.setResizable(false);

frame.setVisible(true);

game.start();

}

}