Avoid iterating through everything

Question

Hello all,
Hope you guys can help me with this problem. I have a program that draws anywhere from 1-300,000 letters on a canvas. Each letter is created from a class called StringState which extends Rectangle. What I would like to do is have each letter respond when the user moves the mouse over the letter by growing bigger. I figured I can just see if the letters bounds contains the point where the mouse moved to and if it does change the letters size and repaint around that letter to update the display. This works great from 1-5000 letters but getting up to 10,000 or even higher creates a very visible lag while the program is iterating through the letters to check if the mouse location intersects the letters bounds. What I was wondering is there a way to get this result without iterating through the entire collection of letters to see if it contains the mouse location? Like can I attach some kind of mouse listener to each letter or something like that? The following program just demonstrates how I create and display the letters I haven't really had a chance to create a demonstration of how they would grow when hovered over. The program i'm working on that actually demonstrates this is very large and hard to trim down to show an example so the following code is actually from a previous question I asked and was provided by Aephyr. Thanks in advance for your guys help :)
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.util.List;
public class PaintSurface implements Runnable, ActionListener {
     public static void main(String[] args) {
          SwingUtilities.invokeLater(new PaintSurface());
     Tableaux tableaux;
     Random random = new Random();
//        Point mouselocation = new Point(0,0);
     static final int WIDTH = 1000;
     static final int HEIGHT = 1000;
        JFrame frame = new JFrame();
     public void run() {
          tableaux = new Tableaux();
          for (int i=15000; --i>=0;)
               addRandom();
          frame.add(tableaux, BorderLayout.CENTER);
          JButton add = new JButton("Add");
          add.addActionListener(this);
          frame.add(add, BorderLayout.SOUTH);
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          frame.setSize(WIDTH, HEIGHT);
          frame.setLocationRelativeTo(null);
//                frame.addMouseMotionListener(new MouseListener());
          frame.setVisible(true);
     public void actionPerformed(ActionEvent e) {
          addRandom();
     void addRandom() {
          tableaux.add(
                    Character.toString((char)('a'+random.nextInt(26))),
                    UIManager.getFont("Button.font"),
                    random.nextInt(WIDTH), random.nextInt(HEIGHT));
//        class MouseListener extends MouseAdapter {
//            public void mouseMoved(MouseEvent e) {
//                mouselocation = new Point(e.getX(),e.getY());
//                frame.repaint();
        class StringState extends Rectangle {
                StringState(String str, Font font, int x, int y, int w, int h) {
                        super(x, y, w, h);
                        string = str;
                        this.font = font;
                String string;
                Font font;
        class Tableaux extends JComponent {
             Tableaux() {
                  this.enableEvents(MouseEvent.MOUSE_MOTION_EVENT_MASK);
                  lagState = createState("Lag", new Font("Arial",Font.BOLD,20), 0, 0);
             protected void processMouseMotionEvent(MouseEvent e) {
                  repaint(lagState);
                  lagState.setLocation(e.getX(), e.getY());
                  repaint(lagState);
                  super.processMouseMotionEvent(e);
             StringState lagState;
                List<StringState> states = new ArrayList<StringState>();
                StringState createState(String str, Font font, int x, int y) {
                    FontMetrics metrics = getFontMetrics(font);
                    int w = metrics.stringWidth(str);
                    int h = metrics.getHeight();
                    return new StringState(str, font, x, y-metrics.getAscent(), w, h);
                public void add(String str, Font font, int x, int y) {
                     StringState state = createState(str, font, x, y);
                        states.add(state);
                        repaint(state);
                protected void paintComponent(Graphics g) {
                        Rectangle clip = g.getClipBounds();
                        FontMetrics metrics = g.getFontMetrics();
                        for (StringState state : states) {
                                if (state.intersects(clip)) {
                                        if (!state.font.equals(g.getFont())) {
                                                g.setFont(state.font);
                                                metrics = g.getFontMetrics();
                                        g.drawString(state.string, state.x, state.y+metrics.getAscent());
                        if (lagState.intersects(clip)) {
                        g.setColor(Color.red);
                        if (!lagState.font.equals(g.getFont())) {
                            g.setFont(lagState.font);
                            metrics = g.getFontMetrics();
                        g.drawString("Lag", lagState.x, lagState.y+metrics.getAscent());
}Here is the code that iterates through the letters to see if a letter contains the mouse location:
            if(e.getSource()==canvas&&edit) {
                for(Letter l : letters) {
                    Rectangle rec = new Rectangle(l.x+l.xoffset,l.y+l.yoffset,l.width,l.height);
                    if(rec.contains(new Point(e.getX(),e.getY()))&&l.resizing==false&&l.defaultSize==l.font.getSize()) {
                        l.resizing = true;
                        new Thread(new ExpandLetter(l)).start();
                    else if(!rec.contains(new Point(e.getX(),e.getY()))&&l.resizing==false){
                        l.font = new Font(l.font.getName(),l.font.getStyle(),l.defaultSize);
                        l.resizeLetter(l.text);
            }However I just learned that this loop itself is taking up a huge amount of memory by saying
l.font = new Font(l.font.getName(),l.font.getStyle(),l.defaultSize); When I take that line out the lag is reduced by a lot. Also I think that it isn't forgetting the "old" letters font that it is replacing by saying new Font() and after running this loop once my program runs slow and laggy as if it doesn't have enough memory to run fast anymore. Is there something I am doing wrong by initiating a new Font. I would have thought that it wouldn't take up anymore memory because it replaces the old font the the letter "l" has. The loop seems to have some kind of memory leak if someone could point it out to me that would be great. Thanks :)
Edited by: neptune692 on Feb 16, 2010 8:18 PM

Answer 1

neptune692 wrote:
can I attach some kind of mouse listener to each letterTry this:
import java.awt.*;
import java.awt.event.*;
import java.awt.font.*;
import java.awt.geom.*;
import javax.swing.*;
import java.util.*;
import javax.swing.event.*;
public class SimplePaintSurface implements Runnable, ActionListener {
    private static final int WIDTH = 1250;
    private static final int HEIGHT = 800;
    private Random random = new Random();
    private JFrame frame = new JFrame("SimplePaintSurface");
    private JPanel tableaux;
    public void run() {
        tableaux = new JPanel(null);
        for (int i = 15000; --i >= 0;) {
            addRandom();
        frame.add(tableaux, BorderLayout.CENTER);
        JButton add = new JButton("Add");
        add.addActionListener(this);
        frame.add(add, BorderLayout.SOUTH);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(WIDTH, HEIGHT);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
        tableaux.requestFocusInWindow();
    public void actionPerformed(final ActionEvent e) {
        addRandom();
        tableaux.repaint();
    void addRandom() {
        Letter letter = new Letter(Character.toString((char) ('a' + random.nextInt(26))));
        letter.setBounds(random.nextInt(WIDTH), random.nextInt(HEIGHT), 16, 16);
        tableaux.add(letter);
    public static void main(final String[] args) {
        SwingUtilities.invokeLater(new SimplePaintSurface());
class Letter extends JLabel {
    Font font1;
    Font font2;
    private final FontRenderContext fontRenderContext1;
    private final FontRenderContext fontRenderContext2;
    public Letter(final String letter) {
        super(letter);
        setFocusable(true);
        setBackground(Color.RED);
        font1 = getFont();
        font2 = font1.deriveFont(48f);
        fontRenderContext1 = getFontMetrics(font1).getFontRenderContext();
        fontRenderContext2 = getFontMetrics(font2).getFontRenderContext();
        MouseInputAdapter mouseHandler = new MouseInputAdapter() {
            @Override
            public void mouseEntered(final MouseEvent e) {
                Letter.this.setOpaque(true);
                setFont(font2);
                Rectangle bounds = getBounds();
                Rectangle2D stringBounds = font2.getStringBounds(getText(), fontRenderContext2);
                bounds.width = (int) stringBounds.getWidth();
                bounds.height = (int) stringBounds.getHeight();
                setBounds(bounds);
            @Override
            public void mouseExited(final MouseEvent e) {
                Letter.this.setOpaque(false);
                setFont(font1);
                Rectangle bounds = getBounds();
                Rectangle2D stringBounds = font1.getStringBounds(getText(), fontRenderContext1);
                bounds.width = (int) stringBounds.getWidth();
                bounds.height = (int) stringBounds.getHeight();
                setBounds(bounds);
        addMouseListener(mouseHandler);
}