Develop Reference

Better way to repaint the jframe

I'm building a project for college and I have several shapes in my frame and I need to do some operations with those objects. for example:
Figure fig = figs.get(figs.size() -1);
fig.mov(dx,dy);
figs.set(figs.size() -1, fig);
repaint();
I have a array of figures and every time I drag/move 1 figure, I have to update that array and also do repaint() and this is going to happen when one of the keyboard arrows get pressed.
My problem here is that despite the repaint() function being fast, when I make several moves of 1 object, the screen goes white several times, making it difficult to see. I don't know a lot of java and I don't have any ideas of how to solve this. I was wondering if anyone has any ideas to help me out, please.
Example:
figurestest/Figure.java
package figurestest;
import java.awt.Graphics;
public abstract class Figure {
public int x, y;
public int w, h;
public Figure (int x, int y, int w, int h) {
this.x = x;
this.y = y;
this.w = w;
this.h = h;
}
public abstract void paint (Graphics g);
public abstract void mov (int dx, int dy);
}
figurestest/rect.java
package figurestest;
import java.awt.*;
public class Rect extends Figure {
public Rect (int x, int y, int w, int h) {
super(x, y, w, h);
}
public void paint (Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.fillRect(this.x, this.y, this.w, this.h);
g2d.drawRect(this.x,this.y, this.w,this.h);
}
public void mov (int dx, int dy){
this.x += dx;
this.y += dy;
}
}
testapp.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.ArrayList;
import java.util.Random;
import figurestest.*;
class TestApp {
public static void main (String[] args) {
ListFrame frame = new ListFrame();
frame.setVisible(true);
}
}
class ListFrame extends JFrame {
ArrayList<Figure> figs = new ArrayList<Figure>();
Random rand = new Random();
ListFrame () {
this.addWindowListener (
new WindowAdapter() {
public void windowClosing (WindowEvent e) {
System.exit(0);
}
}
);
this.addKeyListener (
new KeyAdapter() {
public void keyPressed (KeyEvent evt) {
Dimension size = getContentPane().getSize();
int x = rand.nextInt(size.width);
int y = rand.nextInt(size.height);
int w = 5+ rand.nextInt(50);
int h = 5+ rand.nextInt(50);
if (evt.getKeyChar() == 'r') {
figs.add(new Rect(x,y, w,h));
}
else if (evt.getKeyCode() == KeyEvent.VK_DOWN || evt.getKeyCode() == KeyEvent.VK_LEFT || evt.getKeyCode() == KeyEvent.VK_RIGHT || evt.getKeyCode() == KeyEvent.VK_UP ) {
if (figs.size() > 0){
int dx = 0;
int dy = 0;
if(evt.getKeyCode() == KeyEvent.VK_DOWN) dy = 2;
else if (evt.getKeyCode() == KeyEvent.VK_UP){ dy = -2;}
else if (evt.getKeyCode() == KeyEvent.VK_RIGHT) dx = 2;
else if (evt.getKeyCode() == KeyEvent.VK_LEFT) dx = -2;
Figure fig = figs.get(figs.size() -1);
fig.mov(dx,dy);
figs.set(figs.size() -1, fig);
}
}
repaint();
}
}
);
this.setTitle("Figures");
this.setSize(350, 350);
}
public void paint (Graphics g) {
super.paint(g);
for (Figure fig: this.figs) {
fig.paint(g);
}
}
}

You're making some strange mistakes. Don't extend JFrame it is pointless in this case.
Here is a start. You should probably use something other than a key listener, and make an action instead for the input map instead.
class ListFrame {
ArrayList<Figure> figs = new ArrayList<Figure>();
Random rand = new Random();
ListFrame () {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
JPanel custom = new JPanel(){
#Override
public void paintComponent(Graphics g) {
super.paint(g);
for (Figure fig: figs) {
fig.paint(g);
}
}
#Override
public Dimension getPreferredSize(){
//you custom component should know it's preferred size.
return new Dimension(350, 350);
}
};
frame.addKeyListener (
new KeyAdapter() {
public void keyPressed (KeyEvent evt) {
Dimension size = custom.getSize();
int x = rand.nextInt(size.width);
int y = rand.nextInt(size.height);
int w = 5+ rand.nextInt(50);
int h = 5+ rand.nextInt(50);
if (evt.getKeyChar() == 'r') {
figs.add(new Rect(x,y, w,h));
}
else if (evt.getKeyCode() == KeyEvent.VK_DOWN || evt.getKeyCode() == KeyEvent.VK_LEFT || evt.getKeyCode() == KeyEvent.VK_RIGHT || evt.getKeyCode() == KeyEvent.VK_UP ) {
if (figs.size() > 0){
int dx = 0;
int dy = 0;
if(evt.getKeyCode() == KeyEvent.VK_DOWN) dy = 2;
else if (evt.getKeyCode() == KeyEvent.VK_UP){ dy = -2;}
else if (evt.getKeyCode() == KeyEvent.VK_RIGHT) dx = 2;
else if (evt.getKeyCode() == KeyEvent.VK_LEFT) dx = -2;
Figure fig = figs.get(figs.size() -1);
fig.mov(dx,dy);
//You don't need to set the value. You modified it.
//figs.set(figs.size() -1, fig);
}
}
custom.repaint();
}
}
);
frame.setContentPane(custom);
frame.pack();
frame.setTitle("Figures");
frame.setVisible(true);
}
}

creating many objects with collision properties. JAVA

I have a simple program with three rectangles: one that can move with the push of the arrow keys, and two that are already moving back and forth on their own.
When the 'player' rectangle and top red collide, the player driven rectangle gets put back to (0,0). When I try to collide the player rectangle with the bottom red rectangle, it does not have those collision properties and I have no idea why.
What am I missing?
import java.awt.*;//needed for graphics
import javax.swing.*;//needed for JFrame window
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
public class javaapplication23 extends JFrame implements KeyListener, ActionListener {
public static int x = 0;
public static int y = 0;
public static int x2 = 100;
public static int y2 = 100;
public javaapplication23() {//constructor for JPanel
add(new JP());
}//close Jpanel Contructor
public static void main(String[] args) {
javaapplication23 w = new javaapplication23();
w.setTitle("MIKE IS AWESOME");
w.setSize(Toolkit.getDefaultToolkit().getScreenSize());
w.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
w.setVisible(true);
w.addKeyListener(w);
}
public class JP extends JPanel {//start JPanel CLass
public JP() {
Container c = getContentPane();
c.setBackground(Color.white);//backgraund color can be changed
}
public void paint(Graphics g) {//opens paint method
super.paint(g);
player(g, x, y);
g.setColor(Color.RED);
enemylevel1(g, x2, y2);
Rectangle enemyblocks = new Rectangle(x2, y2, 25, 25);
Rectangle player = new Rectangle(x, y, 25, 25);
enemyblocks.contains(x2, y2);
player.contains(x, y);
if (player.getBounds().intersects(enemyblocks.getBounds())) {
x = 0;
y = 0;
}
pause(1);
repaint();
}//close paint method
}//close JPanel Class
public static void pause(int time) {
try //opens an exception handling statement
{
Thread.sleep(time);
} catch (InterruptedException e) {
} //captures the exception
}
public void actionPerformed(ActionEvent e) {
}
public void keyTyped(KeyEvent e) {
}
public void keyReleased(KeyEvent e) {
}
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == e.VK_RIGHT) {
x += 20;//global variable controlling right movement
repaint();
}
if (e.getKeyCode() == e.VK_LEFT) {
x -= 20;//global variable controlling left movement
repaint();
}
if (e.getKeyCode() == e.VK_UP) {
y -= 20;//global variable controlling up movement
repaint();
}
if (e.getKeyCode() == e.VK_DOWN) {
y += 20;//global variable controlling down movement
repaint();
}
}
public void player(Graphics g, int x, int y) {
g.fillRect(x, y, 30, 30);
}
public void enemylevel1(Graphics g, int x, int y) {
g.fillRect(x2, y2, 25, 25);
g.fillRect(x2, y2 + 100, 25, 25);
if (x2 < 200 && y2 == 100) {
x2 += 1;
}
if (x2 == 200 && y2 >= 100) {
y2 += 1;
}
if (x2 <= 200 && y2 >= 101) {
x2 -= 1;
}
if (x2 == 100 && y2 <= 101) {
y2 -= 1;
}
pause(10);
repaint();
}
}

Start by having a look at Working with Geometry, this will allow you to reduce much of the code complexity.
Basically, a enemy is just a Rectangle, Graphics2D can paint these without to much of an issue. What you need to do is create an instance which can also update it's position based on your needs
public class Enemy extends Rectangle {
private int xDelta;
public Enemy(int x, int y) {
super(x, y, 20, 20);
if (x == 0) {
xDelta = 1;
} else {
xDelta = -1;
}
}
public void update(Rectangle bounds) {
x += xDelta;
if (x < bounds.x) {
x = bounds.x;
xDelta *= -1;
} else if (x > bounds.x + bounds.width - width) {
x = bounds.x + bounds.width - width;
xDelta *= -1;
}
}
}
So, this creates a single unit of work, which is isolated from everything else and carries it's own logic with it. This makes updating it, painting and generally working with much simpler.
Next, you need to create a List of these
public class Bounce extends JPanel implements KeyListener, ActionListener {
private List<Enemy> enemies;
//...
public Bounce() {
enemies = new ArrayList<>(5);
int y = 100;
for (int index = 0; index < 5; index++) {
int x = (index % 2 == 0) ? 0 : 200;
Enemy enemy = new Enemy(x, y);
enemies.add(enemy);
y += 60;
}
This creates a List of Enemys which are distributed evenly within the container.
Now, we need to paint them....
#Override
protected void paintComponent(Graphics g) {//opens paint method
super.paintComponent(g);
Graphics2D g2d = (Graphics2D)g.create();
g2d.setColor(Color.RED);
for (Enemy enemy : enemies) {
g2d.fill(enemy);
}
}//close paint method
nb: General convention suggests that you should override paintComponent when you want to perform custom painting
But they don't move, that kind of sucks. So we need a way to, on a regular bases, update the position of the enemies...
First, we create a simple method which we can call to update the enemies, remember, they are capable of updating themselves, we just need to tell them when
public void updateState() {
Rectangle bounds = new Rectangle(20, 20, 200, 200);
for (Enemy enemy : enemies) {
enemy.update(bounds);
}
}
Remember, the Enemy is self contained, it knows how to update itself based on the constraints you have provided.
And now, we need to call this method on a regular bases...
javax.swing.Timer timer = new javax.swing.Timer(40, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
updateState();
repaint();
}
});
timer.start();
Okay, this will schedule a callback every 40 milliseconds which will allow us to call the updateState method and repaint the component. This is neat because it won't block the Event Dispatching Thread (making our program look like it's hung) but which notifies us within the context of the EDT, making it safe to update the UI from within - WIN/WIN :)
Take a look at Concurrency in Swing and How to use Swing Timers for more details.
Okay, but that doesn't solve the collision...
The player is also a Rectangle, so why not use the same concept we have with the enemies...
public class Bounce extends JPanel implements KeyListener, ActionListener {
private List<Enemy> enemies;
private Rectangle player;
//...
public Bounce() {
player = new Rectangle(0, 0, 30, 30);
enemies = new ArrayList<>(5);
//...
}
#Override
protected void paintComponent(Graphics g) {//opens paint method
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
drawPlayer(g2d);
g2d.setColor(Color.RED);
for (Enemy enemy : enemies) {
g2d.fill(enemy);
if (player.intersects(enemy)) {
player.x = 0;
player.y = 0;
}
}
}//close paint method
public void drawPlayer(Graphics2D g) {
g.fill(player);
}
Which ends up with something like...
This allows you to add/remove enemies as you want and also change the way in which the enemies move, simply and easily
An my "awesome" test code...
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Bounce extends JPanel implements KeyListener, ActionListener {
private List<Enemy> enemies;
private Rectangle player;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new Bounce());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public Bounce() {
player = new Rectangle(0, 0, 30, 30);
enemies = new ArrayList<>(5);
int y = 100;
for (int index = 0; index < 5; index++) {
int x = (index % 2 == 0) ? 0 : 200;
Enemy enemy = new Enemy(x, y);
enemies.add(enemy);
y += 60;
}
setBackground(Color.white);//backgraund color can be changed
Timer timer = new Timer(40, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
updateState();
repaint();
}
});
timer.start();
setFocusable(true);
requestFocusInWindow();
addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
requestFocusInWindow();
}
});
addKeyListener(this);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(240, 400);
}
#Override
protected void paintComponent(Graphics g) {//opens paint method
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
drawPlayer(g2d);
g2d.setColor(Color.RED);
for (Enemy enemy : enemies) {
g2d.fill(enemy);
if (player.intersects(enemy)) {
player.x = 0;
player.y = 0;
}
}
}//close paint method
public void actionPerformed(ActionEvent e) {
}
public void keyTyped(KeyEvent e) {
}
public void keyReleased(KeyEvent e) {
}
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == e.VK_RIGHT) {
player.x += 20;//global variable controlling right movement
}
if (e.getKeyCode() == e.VK_LEFT) {
player.x -= 20;//global variable controlling left movement
}
if (e.getKeyCode() == e.VK_UP) {
player.y -= 20;//global variable controlling up movement
}
if (e.getKeyCode() == e.VK_DOWN) {
player.y += 20;//global variable controlling down movement
}
}
public void drawPlayer(Graphics2D g) {
g.fill(player);
}
public void updateState() {
Rectangle bounds = new Rectangle(20, 20, 200, 200);
for (Enemy enemy : enemies) {
enemy.update(bounds);
}
}
public class Enemy extends Rectangle {
private int xDelta;
public Enemy(int x, int y) {
super(x, y, 20, 20);
if (x == 0) {
xDelta = 1;
} else {
xDelta = -1;
}
}
public void update(Rectangle bounds) {
x += xDelta;
if (x < bounds.x) {
x = bounds.x;
xDelta *= -1;
} else if (x > bounds.x + bounds.width - width) {
x = bounds.x + bounds.width - width;
xDelta *= -1;
}
}
}
}

Java NullPointerException in call to paint()

My program is throwing a NullPointerException error upon trying to call the paint method of a ship.
import java.awt.*;
import java.awt.event.*;
public class Ship extends Polygon implements ActionListener, KeyListener {
final static Point[] shape = new Point[4];
final static Point START_POSITION = new Point(400, 300);
private int windowX;
private int windowY;
Point pull;
public Ship(int maxX, int maxY) {
super(shape, START_POSITION, 0);
windowX = maxX;
windowY = maxY;
shipInit();
init(shape);
Point[] pointArray = getPoints();
pull = new Point(0, 0);
}
public void shipInit() {
shape[0] = new Point(0, 0);
shape[1] = new Point(30, 10);
shape[2] = new Point(0, 20);
shape[3] = new Point(10, 10);
}
public void paint(Graphics brush) {
brush.setColor(Color.white);
Point[] points = getPoints();
if (position.x > windowX) {
position.x -= windowX;
} else if (position.x < 0) {
position.x += windowX;
} else if (position.y > windowY) {
position.y -= windowY;
} else if (position.y < 0) {
position.x += windowY;
}
for (int i = 0; i < points.length; i++) {
int x1;
int y1;
int x2;
int y2;
if (i == points.length - 1) {
x1 = (int) points[i].x;
y1 = (int) points[i].y;
x2 = (int) points[0].x;
y2 = (int) points[0].y;
} else {
x1 = (int) points[i].x;
y1 = (int) points[i].y;
x2 = (int) points[i + 1].x;
y2 = (int) points[i + 1].y;
}
brush.drawLine(x1, y1, x2, y2);
}
}
public void move() {
position.x += 2;
position.y += 5;
// position.y += 1;
}
public void accelerate(double acceleration) {
pull.x += (acceleration * Math.cos(Math.toRadians(rotation)));
pull.y += (acceleration * Math.sin(Math.toRadians(rotation)));
}
public void keyPressed(KeyEvent e) {
int keyPressed = e.getKeyCode();
if (keyPressed == KeyEvent.VK_W)
System.out.println("Hi");
if (keyPressed == KeyEvent.VK_UP) {
accelerate(5);
position.x += pull.x;
position.y += pull.y;
}
if (keyPressed == KeyEvent.VK_RIGHT) {
rotation += 5;
}
if (keyPressed == KeyEvent.VK_LEFT) {
rotation -= 5;
}
}
public void keyReleased(KeyEvent e) {
}
public void keyTyped(KeyEvent e) {
}
#Override
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
}
}
And the class the calls the paint
import java.awt.*;
import java.awt.event.*;
class Asteroids extends Game {
private static int frameWidth = 800;
private static int frameHeight = 600;
Ship player;
public Asteroids() {
super("Asteroids!", frameWidth, frameHeight);
init();
}
public void init() {
player = new Ship(800, 600);
this.addKeyListener(player);
repaint();
}
public void paint(Graphics brush) {
brush.setColor(Color.black);
brush.fillRect(0, 0, width,height);
brush.setColor(Color.white);
String hi = "hi";
brush.drawString(hi, 299, 399);
player.paint(brush);
}
public static void main (String[] args) {
new Asteroids();
}
}
The error says that the error is thrown when calling player.paint(brush). Can anyone figure out why?

I have never coded in this before, but a quick trip to the universe of google explained to me that paint() and init() runs on 2 different threads.
That said, your paint() method gets called BEFORE the init() method.
A quick way to fix this would be to have a boolean that gets set inside init()
Like this:
import java.awt.*;
import java.awt.event.*;
class Asteroids extends Game {
private static int frameWidth = 800;
private static int frameHeight = 600;
Ship player;
private boolean hasInitialized; // Initialization check
public Asteroids() {
super("Asteroids!", frameWidth, frameHeight);
init();
}
public void init() {
player = new Ship(800, 600);
this.addKeyListener(player);
hasInitialized = true; // We set the boolean to true to indicate that we have initialized.
repaint();
}
public void paint(Graphics brush) {
if (!hasInitialized) return; // Nope, not ready yet, we'll stop here.
brush.setColor(Color.black);
brush.fillRect(0, 0, width,height);
brush.setColor(Color.white);
String hi = "hi";
brush.drawString(hi, 299, 399);
player.paint(brush);
}
public static void main (String[] args) {
new Asteroids();
}
}
I'm not 100% certain this will fix it, considering you already have init() inside the constructor.
But it's worth a try!
Source: Java, applet: How to block the activation of paint() before init() finishes it's work

how to space out random circles across a JPanel when using an array

I am trying to draw 7 random circles across a JPanel using an array. I managed to get the array to work but now I am having trouble spacing out the circles. When i run the program i see multiple circles being drawn but they are all on the same spot. All the circles are of different size and color. The other problem i have is making the circles move towards the bottom of the screen.
public class keyExample extends JPanel implements ActionListener, KeyListener{
private Circle[] circles = new Circle[7];
Timer t = new Timer(5,this);
//current x and y
double x = 150, y = 200;
double changeX = 0, changeY = 0;
private int circlex = 0,circley = 0; // makes initial starting point of circles 0
private javax.swing.Timer timer2;
public keyExample(){
t.start();
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
NewCircle();
timer2 = new javax.swing.Timer(33,new MoveListener());
timer2.start();
}
public void NewCircle(){
Random colors = new Random();
Color color = new Color(colors.nextInt(256),colors.nextInt(256),colors.nextInt(256));
Random num= new Random();
int radius = num.nextInt(45);
for (int i = 0; i < circles.length; i++)
circles[i] = new Circle(circlex,circley,radius,color);
}
}
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLUE);
g2.fill(new Rectangle2D.Double(x,y,40,40));
for (int i = 0; i < circles.length; i++)
circles[i].fill(g);
}
public void actionPerformed(ActionEvent e){
repaint();
x += changeX;
y += changeY;
changeX = 0;
changeY = 0;
}
public void up() {
if (y != 0){
changeY = -3.5;
changeX = 0;
}
}
public void down() {
if (y <= 350){
changeY = 3.5;
changeX = 0;
}
}
public void left() {
if (x >= 0) {
changeX = -3.5;
changeY = 0;
}
}
public void right() {
if (x <= 550) {
changeX = 3.5;
changeY = 0;
}
}
private class MoveListener implements ActionListener{
public void actionPerformed(ActionEvent e){
repaint();
Random speed = new Random();
int s = speed.nextInt(8);
}
}
public void keyPressed(KeyEvent e){
int code = e.getKeyCode();
if (code == KeyEvent.VK_UP){
up();
}
if (code == KeyEvent.VK_DOWN){
down();
}
if (code == KeyEvent.VK_RIGHT){
right();
}
if (code == KeyEvent.VK_LEFT){
left();
}
}
public void keyTyped(KeyEvent e) { }
public void keyReleased(KeyEvent e) { }
}
Circle class
import java.awt.*;
public class Circle{
private int centerX, centerY, radius, coord;
private Color color;
public Circle(int x, int y, int r, Color c){
centerX = x;
centerY = y;
radius = r;
color = c;
}
public void draw(Graphics g){
Color oldColor = g.getColor();
g.setColor(color);
g.drawOval(centerX - radius, centerY - radius, radius * 2, radius * 2);
g.setColor(oldColor);
}
public void fill(Graphics g){
Color oldColor = g.getColor();
g.setColor(color);
g.fillOval(centerX - radius, centerY - radius, radius *2, radius * 2);
g.setColor(oldColor);
}
public boolean containsPoint(int x, int y){
int xSquared = (x - centerX) * (x - centerX);
int ySquared = (y - centerY) * (y - centerY);
int RadiusSquared = radius * radius;
return xSquared + ySquared - RadiusSquared <=0;
}
public void move(int xAmount, int yAmount){
centerX = centerX + xAmount;
centerY = centerY + yAmount;
}
}

This is one of the problems with relying on borrowed code that you don't understand...
Basically, all you need to do is change the creation of the circles, for example...
for (int i = 0; i < circles.length; i++) {
circles[i] = new Circle(circlex, circley, radius, color);
circlex += radius;
}
You may wish to re-consider the use of KeyListener, in favour of Key Bindings before you discover that KeyListener doesn't work the way you expect it to...
For some strange reason, you're calling NewCirlces from within the MoveListener's actionPerfomed method, meaning that the circles are simply being re-created on each trigger of the Timer...instead, call it first in the constructor
You're also calling within your paintComponent method...this should mean that the circles never move and instead, random change size...
Updated with runnable example...
I modified your paint code NewCircle and the MoveListener a little...
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Rectangle2D;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class CircleExample extends JPanel implements ActionListener, KeyListener {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new CircleExample());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
private Circle[] circles = new Circle[7];
Timer t = new Timer(5, this);
//current x and y
double x = 150, y = 200;
double changeX = 0, changeY = 0;
private int circlex = 0, circley = 0; // makes initial starting point of circles 0
private javax.swing.Timer timer2;
public CircleExample() {
NewCircle();
t.start();
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
timer2 = new javax.swing.Timer(33, new MoveListener());
timer2.start();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
public void NewCircle() {
for (int i = 0; i < circles.length; i++) {
Random colors = new Random();
Color color = new Color(colors.nextInt(256), colors.nextInt(256), colors.nextInt(256));
Random num = new Random();
int radius = num.nextInt(90);
circles[i] = new Circle(circlex, circley, radius, color);
circlex += radius;
}
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLUE);
g2.fill(new Rectangle2D.Double(x, y, 40, 40));
for (int i = 0; i < circles.length; i++) {
circles[i].fill(g);
}
}
#Override
public void actionPerformed(ActionEvent e) {
repaint();
x += changeX;
y += changeY;
changeX = 0;
changeY = 0;
}
public void up() {
if (y != 0) {
changeY = -3.5;
changeX = 0;
}
}
public void down() {
if (y <= 350) {
changeY = 3.5;
changeX = 0;
}
}
public void left() {
if (x >= 0) {
changeX = -3.5;
changeY = 0;
}
}
public void right() {
if (x <= 550) {
changeX = 3.5;
changeY = 0;
}
}
private class MoveListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
Random speed = new Random();
for (Circle circle : circles) {
int s = speed.nextInt(8);
circle.move(0, s);
}
repaint();
}
}
public void keyPressed(KeyEvent e) {
int code = e.getKeyCode();
if (code == KeyEvent.VK_UP) {
up();
}
if (code == KeyEvent.VK_DOWN) {
down();
}
if (code == KeyEvent.VK_RIGHT) {
right();
}
if (code == KeyEvent.VK_LEFT) {
left();
}
}
public void keyTyped(KeyEvent e) {
}
public void keyReleased(KeyEvent e) {
}
public class Circle {
private int centerX, centerY, radius, coord;
private Color color;
public Circle(int x, int y, int r, Color c) {
centerX = x;
centerY = y;
radius = r;
color = c;
}
public void draw(Graphics g) {
Color oldColor = g.getColor();
g.setColor(color);
g.drawOval(centerX, centerY, radius, radius);
g.setColor(oldColor);
}
public void fill(Graphics g) {
Color oldColor = g.getColor();
g.setColor(color);
g.fillOval(centerX, centerY, radius, radius);
g.setColor(oldColor);
}
public boolean containsPoint(int x, int y) {
int xSquared = (x - centerX) * (x - centerX);
int ySquared = (y - centerY) * (y - centerY);
int RadiusSquared = radius * radius;
return xSquared + ySquared - RadiusSquared <= 0;
}
public void move(int xAmount, int yAmount) {
centerX = centerX + xAmount;
centerY = centerY + yAmount;
}
}
}

Why does the height of the rectangles jump vary?

Why does the height of the rectangle's jump vary? It seems to go in a cycle. First it jumps low then it doesn't jump at all then it jumps high then it doesn't jump at all. i can't figure out why as the same code is used and it is triggered by the same event.
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.KeyEvent;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
#SuppressWarnings("serial")
class Game extends JPanel{
Square square = new Square(this);
Ground ground = new Ground (this);
public Game() {
addKeyListener(new KeyListener() {
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyReleased(KeyEvent e) {
square.keyReleased(e);
}
#Override
public void keyPressed(KeyEvent e) {
square.keyPressed(e);
}
});
setFocusable(true);
}
public static void main(String[] args) throws InterruptedException {
JFrame frame = new JFrame("My Mario");
Game game = new Game();
frame.add(game);
frame.setSize(600, 700);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
while (true) {
game.move();
game.repaint();
Thread.sleep(30);
}
}
private void move() {
square.move();
}
#Override
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
square.paint(g2d);
ground.paint(g2d);
}
}
public class Square {
Square square;
int x,xa;
static int y;
int ya;
private Game game;
public static int fistX,fistY;
static int d = 60;
int wide;
boolean onGround;
public Square(Game game) {
this.game = game;
x = 100;
y = 631;
xa = 0;
ya = 0;
onGround = false;
wide = game.getWidth();
}
public void move() {
if (x + xa > 0 && x + xa < game.getWidth()-30)
x = x + xa;
if (y + ya > 0 && y + ya < game.getHeight()-60){
for(int i=12; i< 0; i--);
ya+=10;
y = y + ya;
}
if ( collision() ) {
y-=10;
onGround = true;
}
Square.y+=10;
}
public void paint(Graphics2D g) {
g.setColor(Color.RED);
g.fillRoundRect(x, y-d, 30, d, 10, 10);
}
private boolean collision() {
return game.ground.getBounds().intersects(getBounds());
}
public Rectangle getBounds() {
return new Rectangle(x, y, 30, 60);
}
public void keyReleased(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_LEFT)
xa=0;
if (e.getKeyCode() == KeyEvent.VK_RIGHT)
xa=0;
if(e.getKeyCode() == KeyEvent.VK_DOWN)
d = 60;
if(e.getKeyCode() == KeyEvent.VK_UP);
}
public void keyPressed(KeyEvent e) {
// TODO Auto-generated method stub
if (e.getKeyCode() == KeyEvent.VK_LEFT)
xa = xa -3;
if (e.getKeyCode() == KeyEvent.VK_RIGHT)
xa = xa + 3;
if(e.getKeyCode() == KeyEvent.VK_DOWN)
d = 30;
if(e.getKeyCode() == KeyEvent.VK_UP)
ya -= 60;
}
}
class Ground {
int y,x,h,w;
public Ground(Game game){
x = 0;
y = game.getHeight()-30;
w = game.getWidth();
h = 30;
}
public void paint(Graphics2D g){
g.setColor(Color.BLACK);
g.fillRect(0, 700, 99999999, 30);
}
public Rectangle getBounds() {
return new Rectangle(0, 700, 99999999, 30);
}
}

Don't block the EDT (Event Dispatch Thread) - the GUI will 'freeze' when that happens. Instead of calling Thread.sleep(n) implement a Swing Timer for repeated tasks like animation. See Concurrency in Swing for more details.
frame.setSize(600, 700); I recommend instead setting a preferred size for the content and packing the frame around it. This suggests a constant size for the game on different PLAFs or OS'.
For Swing components other than top-level containers (e.g JFrame or JWindow), override paintComponent(Graphics) rather than paint(Graphics).
Look into key bindings instead of key listeners for Swing.
The first 3 are implemented, the last one (and other one commented in the code) is TODO - BNI.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class SuperMarioGame extends JPanel {
private static final long serialVersionUID = 1L;
Square square = new Square(this);
Ground ground = new Ground (this);
public SuperMarioGame() {
// TODO Update to Key Bindings
addKeyListener(new KeyListener() {
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyReleased(KeyEvent e) {
square.keyReleased(e);
}
#Override
public void keyPressed(KeyEvent e) {
square.keyPressed(e);
}
});
setFocusable(true);
// Use a listener/timer combo.
ActionListener gameAnimation = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
move();
repaint();
}
};
Timer timer = new Timer(30,gameAnimation);
timer.start();
// Set a preferred size for the panel.
Dimension preferred = new Dimension(600,700);
this.setPreferredSize(preferred);
}
public static void main(String[] args) throws InterruptedException {
JFrame frame = new JFrame("My Mario");
SuperMarioGame game = new SuperMarioGame();
frame.add(game);
// Pack the frame to the preferred size.
frame.pack();
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
private void move() {
square.move();
}
#Override
// for Swing components, generally override
// paintComponent rather than paint
//public void paint(Graphics g) {
public void paintComponent(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
square.paint(g2d);
ground.paint(g2d);
}
}
class Square {
Square square;
int x,xa;
static int y;
int ya;
private SuperMarioGame game;
public static int fistX,fistY;
static int d = 60;
int wide;
boolean onGround;
public Square(SuperMarioGame game) {
this.game = game;
x = 100;
y = 631;
xa = 0;
ya = 0;
onGround = false;
wide = game.getWidth();
}
public void move() {
if (x + xa > 0 && x + xa < game.getWidth()-30)
x = x + xa;
if (y + ya > 0 && y + ya < game.getHeight()-60){
for(int i=12; i< 0; i--);
ya+=10;
y = y + ya;
}
if ( collision() ) {
y-=10;
onGround = true;
}
Square.y+=10;
}
public void paint(Graphics2D g) {
g.setColor(Color.RED);
g.fillRoundRect(x, y-d, 30, d, 10, 10);
}
private boolean collision() {
return game.ground.getBounds().intersects(getBounds());
}
public Rectangle getBounds() {
return new Rectangle(x, y, 30, 60);
}
public void keyReleased(KeyEvent e) {
// TODO Else-if would be better here..
if (e.getKeyCode() == KeyEvent.VK_LEFT)
xa=0;
if (e.getKeyCode() == KeyEvent.VK_RIGHT)
xa=0;
if(e.getKeyCode() == KeyEvent.VK_DOWN)
d = 60;
if(e.getKeyCode() == KeyEvent.VK_UP);
}
public void keyPressed(KeyEvent e) {
// TODO Else-if would be better here..
if (e.getKeyCode() == KeyEvent.VK_LEFT)
xa = xa -3;
if (e.getKeyCode() == KeyEvent.VK_RIGHT)
xa = xa + 3;
if(e.getKeyCode() == KeyEvent.VK_DOWN)
d = 30;
if(e.getKeyCode() == KeyEvent.VK_UP)
ya -= 60;
}
}
class Ground {
int y,x,h,w;
public Ground(SuperMarioGame game){
x = 0;
y = game.getHeight()-30;
w = game.getWidth();
h = 30;
}
public void paint(Graphics2D g){
g.setColor(Color.BLACK);
g.fillRect(0, 700, 99999999, 30);
}
public Rectangle getBounds() {
return new Rectangle(0, 700, 99999999, 30);
}
}

Don't block the Event Dispatching Thread any way, it will prevent the EDT from processing repaint requests (and other events) which will make it look like your program has crashed. Have a read of Concurrency in Swing for more information.
Only modify the UI from the EDT, NEVER from any other thread, this includes creating UI elements
Favor key bindings over KeyListeners, they are more capable of resolving focus issues amongst other things. Have a read of How to Use Key Bindings for more details
Favor overriding paintComponent rather then paint. Paint does a lot of important work which you should avoid messing with if you can. Apart from any thing else paintComponent is going to be included in the double buffering of the component where as paint isn't (as super.paint sets it up)
Avoid using static state variables where possible
I don't know if this was deliberate or not, but, for (int i = 12; i < 0; i--); isn't going to achive anything, as the semi colen at the end means, do nothing for a count of 1
Personally, try not to use absolute values for things like width and height, which is actually reliant on parent container. You should also, where possible, provide sizing hints to allow the parent container to make better decisions on how much space it actually needs
UPDATED
Fixed bug in my movement code :P
I had a look at your collision detection code (in move) and, frankly, couldn't make heads or tails of it. I corrected it as well as changed in the way the paint method works so that x,y is always the top, left corner
public class TestGame {
public static void main(String[] args) throws InterruptedException {
new TestGame();
}
public TestGame() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
} catch (InstantiationException ex) {
} catch (IllegalAccessException ex) {
} catch (UnsupportedLookAndFeelException ex) {
}
Game game = new Game();
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(game);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class GameThread extends Thread {
private Game game;
public GameThread(Game game) {
setDaemon(false);
this.game = game;
}
#Override
public void run() {
while (true) {
game.move();
try {
long startedAt = System.currentTimeMillis();
SwingUtilities.invokeAndWait(new Runnable() {
#Override
public void run() {
game.repaint();
}
});
long completedAt = System.currentTimeMillis();
long sleepFor = 30 - (completedAt - startedAt);
if (sleepFor < 0) {
sleepFor = 30;
}
Thread.sleep(sleepFor);
} catch (Exception exp) {
exp.printStackTrace();
}
}
}
}
public class Game extends JPanel {
Square square = new Square(this);
Ground ground = new Ground(this);
public Game() {
// addKeyListener(new KeyListener() {
// #Override
// public void keyTyped(KeyEvent e) {
// }
//
// #Override
// public void keyReleased(KeyEvent e) {
// square.keyReleased(e);
// }
//
// #Override
// public void keyPressed(KeyEvent e) {
// square.keyPressed(e);
// }
// });
setFocusable(true);
InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, false), "press-left");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, false), "press-right");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, false), "press-down");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, false), "press-up");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, true), "release-left");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, true), "release-right");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, true), "release-down");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, true), "release-up");
am.put("press-left", new PressLeftAction(square));
am.put("press-right", new PressRightAction(square));
am.put("press-down", new PressDownAction(square));
am.put("press-up", new PressUpAction(square));
am.put("release-left", new ReleaseLeftAction(square));
am.put("release-right", new ReleaseRightAction(square));
am.put("release-down", new ReleaseDownAction(square));
am.put("release-up", new ReleaseUpAction(square));
new GameThread(this).start();
// public void keyReleased(KeyEvent e) {
//
//
//
// if (e.getKeyCode() == KeyEvent.VK_LEFT) {
// xa = 0;
// }
//
// if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
// xa = 0;
// }
// if (e.getKeyCode() == KeyEvent.VK_DOWN) {
// d = 60;
// }
//
// if (e.getKeyCode() == KeyEvent.VK_UP);
// }
//
// public void keyPressed(KeyEvent e) {
//// TODO Auto-generated method stub
// if (e.getKeyCode() == KeyEvent.VK_LEFT) {
// xa = xa - 3;
// }
//
// if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
// xa = xa + 3;
// }
//
// if (e.getKeyCode() == KeyEvent.VK_DOWN) {
// d = 30;
// }
//
// if (e.getKeyCode() == KeyEvent.VK_UP) {
// ya -= 60;
// }
//
//
//
//
//
// }
}
public void move() {
square.move();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
// Don't override paint, use paintComponent instead
// #Override
// public void paint(Graphics g) {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
square.paint(g2d);
ground.paint(g2d);
g2d.dispose();
}
}
public class Square {
Square square;
private int x, xa;
// static int y;
private int y;
private int ya;
private Game game;
// public static int fistX, fistY;
private int fistX, fistY;
// static int d = 60;
private int d = 60;
private int wide;
private boolean onGround;
public Square(Game game) {
this.game = game;
x = 100;
y = 100;
xa = 0;
ya = 0;
onGround = false;
wide = game.getWidth();
}
public void move() {
y += ya;
x += xa;
if (x < 0) {
x = 0;
} else if (x + 30 > game.getWidth()) {
x = game.getWidth() - 30;
}
if (y < 0) {
y = 0;
} else if (collision()) {
onGround = true;
y = game.ground.getBounds().y - d;
}
// if (x + xa > 0 && x + xa < game.getWidth() - 30) {
// x = x + xa;
// }
//
// if (y + ya > 0 && y + ya < game.getHeight() - 60) {
// // This was never going to do anything, look at the
// // end of the line...the `;` is going to prevent the
// // statemt ya += 10 from begin called within the loop
//// for (int i = 12; i < 0; i--);
// for (int i = 12; i < 0; i--) {
// ya += 10;
// }
// y = y + ya;
// }
// if (collision()) {
// y -= 10;
// onGround = true;
//
// }
//
// y += 10;
}
public void paint(Graphics2D g) {
g.setColor(Color.RED);
System.out.println(x + "x" + (y - d));
g.fillRoundRect(x, y, 30, d, 10, 10);
}
private boolean collision() {
return game.ground.getBounds().intersects(getBounds());
}
public Rectangle getBounds() {
return new Rectangle(x, y, 30, 60);
}
}
public class Ground {
private Game game;
public Ground(Game game) {
this.game = game;
}
public void paint(Graphics2D g) {
g.setColor(Color.BLACK);
g.fillRect(0, game.getHeight() - 30, game.getWidth(), 30);
}
public Rectangle getBounds() {
return new Rectangle(0, game.getHeight() - 30, game.getWidth(), 30);
}
}
public abstract class AbstractSquareAction extends AbstractAction {
private Square square;
public AbstractSquareAction(Square square) {
this.square = square;
}
public Square getSquare() {
return square;
}
}
public class PressLeftAction extends AbstractSquareAction {
public PressLeftAction(Square square) {
super(square);
}
#Override
public void actionPerformed(ActionEvent e) {
getSquare().xa = -3;
System.out.println("pressLeft");
}
}
public class PressRightAction extends AbstractSquareAction {
public PressRightAction(Square square) {
super(square);
}
#Override
public void actionPerformed(ActionEvent e) {
getSquare().xa = 3;
}
}
public class PressDownAction extends AbstractSquareAction {
public PressDownAction(Square square) {
super(square);
}
#Override
public void actionPerformed(ActionEvent e) {
getSquare().ya = 30;
}
}
public class PressUpAction extends AbstractSquareAction {
public PressUpAction(Square square) {
super(square);
}
#Override
public void actionPerformed(ActionEvent e) {
getSquare().ya -= 30;
}
}
public class ReleaseLeftAction extends AbstractSquareAction {
public ReleaseLeftAction(Square square) {
super(square);
}
#Override
public void actionPerformed(ActionEvent e) {
getSquare().xa = 0;
}
}
public class ReleaseRightAction extends AbstractSquareAction {
public ReleaseRightAction(Square square) {
super(square);
}
#Override
public void actionPerformed(ActionEvent e) {
getSquare().xa = 0;
}
}
public class ReleaseDownAction extends AbstractSquareAction {
public ReleaseDownAction(Square square) {
super(square);
}
#Override
public void actionPerformed(ActionEvent e) {
getSquare().ya = 0;
}
}
public class ReleaseUpAction extends AbstractSquareAction {
public ReleaseUpAction(Square square) {
super(square);
}
#Override
public void actionPerformed(ActionEvent e) {
getSquare().ya = 0;
}
}
}