Develop Reference

Did I correctly translate this pseudocode into Java?

I asked this question on Math.se a few days ago, and got the following answer in pseudocode:
Function RandomCircleInside(centerX, centerY, radius):
Let newRadius = radius * Random()
Let radians = 2.0 * 3.14159265358979323846 * Random()
Let deviation = (radius - newRadius) * Sqrt(Random())
Let newX = centerX + deviation * Cos(radians)
Let newY = centerY + deviation * Sin(radians)
Return (newX, newY, newRadius)
End Function
I changed the pseudocode to Java and added my own changes to fit my needs. The new code looks like this:
Circle createNewCircle(int centerX, int centerY, int radius, int newR, Color newColor) {
int newRadius = radius * Random();
double radians = 2.0 * 3.141592653589793 * Random();
double deviation = (radius - newRadius) * Math.sqrt(Random());
System.out.println(radius + " - " + newRadius + " * sqrt(0 or 1) = " + (radius-newRadius) + " * (0 or 1) = " + deviation);
double newX = centerX + deviation * Math.cos(radians);
System.out.println(centerX + " + " + deviation + " * cos(" + radians + ") = " + (centerX + deviation) + " * " + Math.cos(radians));
double newY = centerY + deviation * Math.sin(radians);
int newCirX = (int) newX;
int newCirY = (int) newY;
Circle newCir = new Circle(newCirX, newCirY, newR*2, newR*2, newR, newColor, true);
return newCir;
}
The code itself is supposed to create a new Circle inside of a preexisting one. I created a circle class that looks like this:
import java.awt.Color;
import java.awt.Graphics;
public class Circle {
public int X, Y, Width, Height, radius;
public Color color;
public boolean toFill;
public Circle(int x, int y, int width, int height, int radius, Color color, boolean fill) {
X = x;
Y = y;
Width = width;
Height = height;
this.radius = radius;
this.color = color;
toFill = fill;
}
public void render(Graphics g) {
g.setColor(color);
for(int i=-5; i<5; i++) {
if(toFill) {
g.fillOval(X+i, Y+i, Width-i, Height-i);
} else {
g.drawOval(X+i, Y+i, Width-i, Height-i);
}
}
}
public boolean contains(Circle pBound) {
int pBoundCenterX = pBound.X+pBound.radius;
int cirCenterX = X+radius;
int diffBetweenCentersX = Math.abs(pBoundCenterX-cirCenterX);
int pBoundCenterY = pBound.Y+pBound.radius;
int cirCenterY = Y+radius;
int diffBetweenCentersY = Math.abs(pBoundCenterY-cirCenterY);
if(diffBetweenCentersX<= (pBound.radius+radius) && diffBetweenCentersX>=Math.abs(pBound.radius-radius)) { // X
if(diffBetweenCentersY>=Math.abs(pBound.radius-radius)) { // Y
return true;
}
}
return false;
}
public int getX() {
return X;
}
public int getWidth() {
return Width;
}
public int getRadius() {
return radius;
}
public void setWidth(int width) {
Width = width;
}
public int getHeight() {
return Height;
}
public void setHeight(int height) {
Height = height;
}
public void setX(int x) {
X = x;
}
public int getY() {
return Y;
}
public void setY(int y) {
Y = y;
}
}
My way of creating the new circle is this:
if(secInGame==timesForCircle[X] && !hasChanged) { // circle 2
Circle cir1 = cir;
cir = createNewCircle(cir1.X+(cir1.Width/2), cir1.Y+(cir1.Height/2), cir1.getRadius(), 135, Color.cyan);
hasChanged = true;
circleOn++;
circ++;
}
Where cir1 is the preexisting Circle and cir is the new circle.
Is there anything I didn't code correctly? I've tried a few different variations, but they all give the same result.
Before I implemented the pseudocode, my circles looked like this:
but now it looks like this:
All of my code can be found on github at: link

I think there are several issues in your code.
1. First of all it is not clear why your Circle has radius, Width and Height. For a circle all 3 things should be the same. Also your render in case toFill is true looks strange. Here is a simplified version (note: I didn't compile it so there might be some bugs):
public class Circle {
public int X, Y, radius;
public Color color;
public boolean toFill;
public Circle(int x, int y, int radius, Color color, boolean fill) {
X = x;
Y = y;
this.radius = radius;
this.color = color;
toFill = fill;
}
public void render(Graphics g) {
g.setColor(color);
final int r2 = 2*radius;
if(toFill) {
g.fillOval(X, Y, r2, r2);
}
else {
for(int i=-5; i<5; i++) {
g.drawOval(X+i, Y+i, r2-i, r2-i);
}
}
}
public boolean contains(Circle pBound) {
int pBoundCenterX = pBound.X+pBound.radius;
int cirCenterX = X+radius;
int diffBetweenCentersX = Math.abs(pBoundCenterX-cirCenterX);
int pBoundCenterY = pBound.Y+pBound.radius;
int cirCenterY = Y+radius;
int diffBetweenCentersY = Math.abs(pBoundCenterY-cirCenterY);
if(diffBetweenCentersX<= (pBound.radius+radius) && diffBetweenCentersX>=Math.abs(pBound.radius-radius)) { // X
if(diffBetweenCentersY>=Math.abs(pBound.radius-radius)) { // Y
return true;
}
}
return false;
}
public int getX() {
return X;
}
public int getRadius() {
return radius;
}
public void setX(int x) {
X = x;
}
public int getY() {
return Y;
}
public void setY(int y) {
Y = y;
}
}
I didn't check your code, but I'd consider as a good practice:
renaming x and y into leftX and topY to avoid confusion with centerX/centerY meaning. Or change meaning to more typical center one.
declaring all your fields as private (see encapsulation);
declaring all your fields as final and remove all the setXyz methods (see immutability)
2. I don't understand why your createNewCircle has newR parameter and at the same time you generate a random newRadius in the first line. One of these definitely should be removed. Given that the parameter is always a constant 135 I think it should be removed.
3. Now I believe the main bug in your translation is in the lines
int newCirX = (int) newX;
int newCirY = (int) newY;
It probably should be something like
int newCirX = (int) newX - newRadius;
int newCirY = (int) newY - newRadius;
It looks like you messed with center vs top-left. Actually I think the fact that you made such a bug is an argument that supports renaming x and y I suggested in item #1.

Java paint program double buffering

So I'm working on a paint program in school and now I have to double buffer it. After a week of searching and using tutorials online I am still unable to double buffer my program properly... I have written a double buffer function but then you can't paint anything... When i disable the double buffer you can paint fine but the screen flickers. Please help
(Yes I am aware that some of my code is deprecated and I should fix that)
Code:
import java.applet.*;
import java.awt.*;
public class PaintRun extends Applet
{
static int posx = 0;
static int posy = 0;
static int posxOld = 0;
static int posyOld = 0;
static int size = 20;
static int toolNum = 0;
static boolean ready = false;
static Color col = new Color(120,120,120);
static Button clear = new Button(0,0,20,'C');
static Button sizeInc = new Button(20,0,20,'+');
static Button sizeDec = new Button(40,0,20,'-');
static Tools tool = new Tools(posx,posy);
public void paint(Graphics g)
{
drawButtons(g);
detectButtons(g);
}
private static void detectButtons(Graphics g)
{
if (clear.detect(posx,posy) == true)
{
g.setColor(Color.WHITE);
g.fillRect(0, 0, 800000, 800000);
drawButtons(g);
}
else if (sizeInc.detect(posx, posy))
{
size+=2;
drawButtons(g);
}
else if (sizeDec.detect(posx, posy))
{
size-=2;
if (size <= 2)
size = 2;
drawButtons(g);
}
else
{
if (ready == true)
{
g.setColor(Color.BLACK);
g.drawLine(posxOld, posyOld, posx, posy);
drawButtons(g);
}
}
}
private static void drawButtons(Graphics g)
{
clear.setColor(col, Color.BLACK);
sizeInc.setColor(col, Color.BLACK);
sizeDec.setColor(col, Color.BLACK);
clear.drawButton(g);
sizeInc.drawButton(g);
sizeDec.drawButton(g);
}
public boolean mouseDown(Event e, int x, int y)
{
posx = x;
posy = y;
posxOld = x;
posyOld = y;
ready = true;
repaint();
return true;
}
public boolean mouseDrag(Event e, int x, int y)
{
posxOld = posx;
posyOld = posy;
posx = x;
posy = y;
repaint();
return true;
}
// Normal Update function
public void update(Graphics g)
{
paint(g);
}
// Double buffered Update function
/*public void update(Graphics g)
{
Graphics offgc;
Image offscreen = null;
Dimension d = size();
offscreen = createImage(d.width, d.height);
offgc = offscreen.getGraphics();
offgc.setColor(getBackground());
offgc.fillRect(0, 0, d.width, d.height);
offgc.setColor(getForeground());
paint(offgc);
g.drawImage(offscreen, 0, 0, this);
}
*/
}
class Button extends Applet
{
int minX; // X coord where the button is drawn
int minY; // Y coord where the button is drawn
int maxX; // X size
int maxY; // Y size
char letter;
Color back;
Color line;
// Constructor block
public Button(char desc)
{
minX = 0;
minY = 0;
maxX = 40;
maxY = 40;
back = new Color(255,255,255);
line = new Color(0,0,0);
letter = desc;
}
public Button(int x, int y, char desc)
{
minX = x;
minY = y;
maxX = 40;
maxY = 40;
back = new Color(255,255,255);
line = new Color(0,0,0);
letter = desc;
}
public Button(int x, int y, int size, char desc)
{
minX = x;
minY = y;
maxX = size;
maxY = size;
back = new Color(255,255,255);
line = new Color(0,0,0);
letter = desc;
}
public Button(int x, int y, int sizeX, int sizeY, char desc)
{
minX = x;
minY = y;
maxX = sizeX;
maxY = sizeY;
back = new Color(255,255,255);
line = new Color(0,0,0);
letter = desc;
}
// Draws the button
public void drawButton(Graphics g)
{
g.setColor(back);
g.fillRect(minX, minY, maxX, maxY);
g.setColor(line);
g.drawRect(minX, minY, maxX, maxY);
g.drawString(Character.toString(letter), (minX+maxX/2)-4, (minY+maxY/2)+4);
}
// Sets the button colors
public void setColor(Color b, Color l)
{
back = b;
line = l;
}
// Detects if those coordinates are in the button location or not
public boolean detect(int x, int y)
{
boolean flag = false;
if (x > minX && x < (minX + maxX) && y > minY && y < (minY + maxY))
flag = true;
else
flag = false;
return flag;
}
}

Draw lines between points, each moving in random direction

I'm working on a Java Game using LWJGL. I made a particle system and would like to obtain same result as found on this website: http://play.cubedpixels.de
This is what I got so far:
I tried my best and the problem is it's stopping and they are only moving in one direction. Also the lines are not like on this website. On the website it's smoother and better. They are using OpenGL too.
How to solve these problems and make my implementation better, more like it is one the website?
The code below shows two classes: ParticleGalaxy and Particle. Latter one is inner class of the former, but for clarity I've split them into separate snippets.
ParticleGalaxy:
public class ParticleGalaxy
{
private int count;
private int width;
private int height;
private int mousex;
private int mousey;
public ArrayList<Particle> particles = new ArrayList();
private Random random = new Random();
private TimerUtil timer = new TimerUtil();
int state = 0;
int a = 255;
int r = 255;
int g = 0;
int b = 0;
public ParticleGalaxy(int count, int width, int height)
{
this.count = count;
this.width = width;
this.height = height;
for(int i = 0; i < count; i++)
{
this.particles.add(
new Particle(this.random.nextInt(width),
this.random.nextInt(height)));
}
}
public void drawParticles(int mousex, int mousey)
{
this.mousex = mousex;
this.mousey = mousey;
for(Particle p : this.particles)
{
if(p.reset)
{
p.resetPosSize();
p.reset = false;
}
int x = Math.abs(p.getX() - mousex);
int y = Math.abs(p.getY() - mousey);
if((x < 40 && x > -40) && (y<35 && y>-40))
{
p.setConnect(true);
}
else
{
p.setConnect(false);
}
p.draw();
}
}
}
Particle:
public class Particle
{
private int x;
private int y;
private int k;
private int movey;
private int movex;
private int starty;
private int startx;
private int locationy;
private int locationx;
private float size;
private boolean reset;
private boolean connect;
private Random random = new Random();
private TimerUtil timer = new TimerUtil();
private boolean moving = false;
private boolean start = false;
public Particle(int x, int y)
{
this.x = x;
this.y = y;
this.startx = x;
this.starty = y;
this.size = genRandom(0.57F, 0.71F);
}
public void setConnect(boolean bool)
{
connect = bool;
}
public int getX()
{
return x;
}
public int getY()
{
return y;
}
private void drawLine(int xto, int yto, int xfrom, int yfrom)
{
GL11.glLineWidth(1.2f);
GL11.glColor3f(1.0f, 1.0f, 1.0f);
GL11.glBegin(GL11.GL_LINE_STRIP);
GL11.glVertex2d(xto, yto);
GL11.glVertex2d(xfrom, yfrom);
GL11.glEnd();
}
public void draw()
{
if(!start)
{
start = true;
movex = height - random.nextInt(height);
movey = width - random.nextInt(width);
move(startx, starty, movex, movey);
}
float speed = 1;
float elapsed = 0.01f;
// On starting movement
float distance = (float)Math.sqrt(Math.pow(movex - startx, 2) +
Math.pow(movey - starty, 2));
float directionX = (movex - startx) / distance;
float directionY = (movey - starty) / distance;
if(moving == true)
{
x += directionX * speed * elapsed;
y += directionY * speed * elapsed;
if(Math.sqrt(Math.pow(x - startx, 2) + Math.pow(y - starty, 2)) >= distance)
{
x = (int)movex;
y = (int)movey;
resetPosSize();
this.reset = true;
moving = false;
}
}
this.k += 1;
int xx = 0;
int yy = 0;
this.locationx = this.x + xx;
this.locationy = this.y + yy;
if(locationx < 0 || locationy < 0)
this.reset = true;
if(locationx > width || locationy > height)
this.reset = true;
GuiUtils.drawCircle(this.x + xx, this.y + yy, this.size, -1);
if(connect)
{
for(Particle p : particles)
{
if(p.connect)
drawLine(locationx, locationy, p.locationx, p.locationy);
}
}
}
public void move(int startX, int startY, int endX, int endY)
{
x = (int)startX;
y = (int)startY;
moving = true;
}
public void resetPosSize()
{
this.x = this.random.nextInt(ParticleGalaxy.this.width);
this.y = this.random.nextInt(ParticleGalaxy.this.height);
startx = x;
starty = y;
movex = height - random.nextInt(height);
movey = width - random.nextInt(width);
move(startx, starty, movex, movey);
}
public float genRandom(float min, float max)
{
return (float)(min + Math.random() * (max - min + 1.0F));
}
}

Bullets are not showing up across network client screen in game

Hi all so I a tank war game thats ran over a network and is multiplayer, however whenever I fire a bullet it shows on my screen but not the other player's screen. Can you help, here's a snippet of code form where i think the problem is coming from:
class Tank implements Ball {
double locX, locY, radius, angle;
int self; // index of this tank in WarPanel.tanks
public boolean turnL, turnR, forth, back, fire;
boolean prevtL, prevtR, prevfo;
Color color;
Image image;
public static final double twoPi = Math.PI * 2.0;
public static final double turnRate = Math.PI / 8;
public static final double speed = 4.0;
public static final int RELOAD = 8; // delay between bullets
int count; // timer for reloading
public static final int MAXBULLETS = 7; // max simultaneous shots
Bullet bullets[] = new Bullet[MAXBULLETS];
AffineTransform saveAT; // place to hold current affine transform
public Tank(double x, double y, double a, int index, Image im){
locX = x;
locY = y;
angle = a;
self = index;
image = im;
radius = 22;
// create bullets for this tank
for (int i = 0; i < bullets.length; i++)
bullets[i] = new Bullet(self);
}
public double getX() { return locX; }
public double getY() { return locY; }
public double getRadius() { return radius; }
public boolean isAlive() { return true; }
void update(Boolean local) {
if (turnL)
turnLeft(turnRate);
if (turnR)
turnRight(turnRate);
if (forth){
moveForward();
// Check for rocks
if (WarPanel.hitAnItem(this, WarPanel.rocks) >= 0)
backUp();
}
if (local){
if (turnL != prevtL){
WarPanel.send("turnL "+turnL+" "+locX+" "+locY+" "+angle);
prevtL = turnL;
}
if (turnR != prevtR){
WarPanel.send("turnR "+turnR+" "+locX+" "+locY+" "+angle);
prevtR = turnR;
}
if (forth != prevfo){
WarPanel.send("forth "+forth+" "+locX+" "+locY+" "+angle);
prevfo = forth;
}
}
if (fire){
fireBullet();
}
// Update all of our bullets
for (Bullet b: bullets)
b.update();
}
public void processMove(String s){
// Update movement parameters based on s
Scanner sc = new Scanner(s);
// Get the flag change
String command = sc.next();
boolean value = sc.nextBoolean();
if (command.equals("turnL"))
turnL = value;
else if (command.equals("turnR"))
turnR = value;
else if (command.equals("forth"))
forth = value;
else
System.out.println("Unexpected move: "+command);
// then unpack position update
locX = sc.nextDouble();
locY = sc.nextDouble();
angle = sc.nextDouble();
}
void paint(Graphics g){
// Use the affine transform feature in Graphics2D
// to easily rotate the tank's image.
Graphics2D g2 = (Graphics2D)g;
saveAT = g2.getTransform();
g2.translate(locX, locY);
g2.rotate(angle);
g2.drawImage(image, (int)(-radius), (int)(-radius), null);
// Reset the transform (this is important)
g2.setTransform(saveAT);
// Then draw bullets
for (Bullet b: bullets)
b.paint(g2);
}
void fireBullet(){
// If it has been long enough since the last shot...
count--;
if (count > 0) return;
// ...and if all the bullets aren't currently in use...
int slot = getAvailableBullet();
if (slot < 0)
return;
// ...then launch a new bullet
bullets[slot].setLocation(locX, locY);
bullets[slot].setDirection(angle);
bullets[slot].reset();
// Reset the timer
count = RELOAD;
}
int getAvailableBullet(){
for (int i = 0; i < bullets.length; i++)
if (!bullets[i].isAlive())
return i;
return -1;
}
void turnRight(double a){
angle += a;
if (angle > twoPi)
angle -= twoPi;
}
void turnLeft(double a){
angle -= a;
if (angle < 0.0)
angle += twoPi;
}
void moveForward(){
locX += speed*Math.cos(angle);
locY += speed*Math.sin(angle);
}
void backUp(){
locX -= speed*Math.cos(angle);
locY -= speed*Math.sin(angle);
}
}

How to make a collision detection in java?

I have a two image that moves in a random direction. Now, if that images would bump each other I want it to disappear and that is my problem about making a collision detection. Could someone help me about this problem?
Here is the code:
public class HumanBeing extends Sprite implements ImageObserver
{
private java.awt.Image humanImage;
private final World world;
private double x;
private double y;
private double speed;
private double direction = 1;
private java.util.List<Sprite> objects = new ArrayList<Sprite>();
private double angle;
public HumanBeing(World world, double x, double y, double speed)
{
this.world =world;
this.x = x;
this.y = y;
this.speed = convertToMeterPerSecond(speed);
URL iU = this.getClass().getResource("human.jpg");
ImageIcon icon = new ImageIcon(iU);
humanImage = icon.getImage();
objects.add(this);
}
public Image getImage()
{
return humanImage;
}
#Override
public void move(long dt)
{
double dt_s = dt / 1e9;
double dx_m = speed * dt_s * Math.sin(angle);
double dy_m = speed * dt_s * Math.cos(angle);
final double right_wall = world.x1_world;
final double up_wall = world.y1_world;
final double down_wall = 0.0;
final double left_wall = 0.0;
x += dx_m;
y += dy_m;
if (x >= right_wall)
{
setRandomDirection();
}
if (y > up_wall)
{
setRandomDirection();
}
if (x <= left_wall)
{
setRandomDirection();
}
if (y < down_wall)
{
setRandomDirection();
}
}
public void setRandomDirection()
{
HumanBeing humanbeing = this;
humanbeing.setAngle(Math.PI * 2 * Math.random());
}
#Override
public void render(Graphics2D g2d)
{
AffineTransform t = g2d.getTransform();
final double humanHeight = 1.6;// meter
final double humanWidth = 1.8; //meter
final double foot_position_y = humanHeight;
final double foot_position_x = humanWidth / 2;
int xx = world.convertToPixelX(x - foot_position_x); // to find the upper-left corner
int yy = world.convertToPixelY(y + foot_position_y); // to find the upper-left corner
g2d.translate(xx, yy);
// ratio for actual Image size
double x_expected_pixels = humanHeight * board.meter;
double y_expected_pixels = humanWidth * board.meter;
double w = ((ToolkitImage) humanImage).getWidth();
double h = ((ToolkitImage) humanImage).getHeight();
double x_s = x_expected_pixels / w;
double y_s = y_expected_pixels / h;
g2d.scale(x_s, y_s);
g2d.drawImage(getImage(), 0, 0, this); // upper left corner
g2d.setColor(Color.BLACK);
g2d.setTransform(t);
}
#Override
public void moveAt(double distance_x, double distance_y)
{
this.x = distance_x;
this.y = distance_y;
}
#Override
public boolean imageUpdate(Image img, int infoflags, int x, int y, int width, int height)
{
return false;
}
public void setAngle(double angle)
{
this.angle = angle;
}
}
this is my HumanBeing class
public class Chicken extends Sprite implements ImageObserver
{
private java.awt.Image chickenImage;
private final World world;
private double x;
private double y;
private double speed;
private double angle;
public Chicken(World world, double x, double y, double speed)
{
this.world = world;
this.x = x;
this.y = y;
this.speed = convertToMeterPerSecond(speed);
URL iU = this.getClass().getResource("chicken.gif");
ImageIcon icon = new ImageIcon(iU);
chickenImage = icon.getImage();
}
public Image getImage()
{
return chickenImage;
}
public void move(long dt)
{
double dt_s = dt / 1e9;
double dx_m = speed * dt_s * Math.sin(angle);
double dy_m = speed * dt_s * Math.cos(angle);
final double right_wall = world.x1_world;
final double up_wall = world.y1_world;
final double down_wall = 0.0;
final double left_wall = 0.0;
x += dx_m;
y += dy_m;
if (x >= right_wall)
{
x = right_wall;
setRandomDirection();
}
if (y > up_wall)
{
y = up_wall;
setRandomDirection();
}
if (x <= left_wall)
{
x = left_wall;
setRandomDirection();
}
if (y < down_wall)
{
y = down_wall;
setRandomDirection();
}
}
public void setRandomDirection()
{
Chicken chicken = this;
chicken.setAngle(Math.PI * 2 * Math.random());
}
#Override
public void render(Graphics2D g2d)
{
AffineTransform t = g2d.getTransform();
double height = 0.3; //meter
double width = 0.3; //meter
double chicken_footy = height;
double chicken_footx = width/2;
int xx = world.convertToPixelX(x - chicken_footx);
int yy = world.convertToPixelY(y + chicken_footy);
g2d.translate(xx, yy);
double x_expected_pixels = width * board.meter;
double y_expected_pixels = height * board.meter;
double x_s = x_expected_pixels / ((ToolkitImage) chickenImage).getWidth();
double y_s = y_expected_pixels / ((ToolkitImage) chickenImage).getHeight();
g2d.scale(x_s, y_s);
g2d.drawImage(getImage(), 0, 0, this);
g2d.setColor(Color.BLACK);
g2d.setTransform(t);
}
public void moveAt(double distance_x, double distance_y)
{
this.x = (int) distance_x;
this.y = (int) distance_y;
}
#Override
public boolean imageUpdate(Image img, int infoflags, int x, int y, int width, int height)
{
return true;
}
public void setAngle(double angle)
{
this.angle = angle;
}
}
this is my chicken class

Draw invisible Rectangle around your sprites as like Box's and than use below method to check whether they are intersecting or not :)
http://download.oracle.com/javase/1.4.2/docs/api/java/awt/Rectangle.html#intersects(java.awt.Rectangle)
if(rect.intersect(anotherRect))
{
disappear();
}
Good luck