i found this code for pacman i want some one to explain me how it works i am new to java game programming so my doubts might be silly for few of u
i just understood the array part of creating the maze i have written all my doubts
thank u very much in advance for helping me out
my doubts are
1.what is pacanimcount,pacanimdelay,pacanimdir,pacmananimpos used for exactlyis it like dir for direction and pos for position?
2.dx,dy?
3.what is DoAnim method actually doing?

4.in showintroscreen method y is this guy making it complicated by keeping "g2d.setColor(new Color(0, 32, 48));"is there any reason behind it?
5.y is he using "g2d.fillRect(50, scrsize / 2 - 30, scrsize - 100, 50);"cant we just give normal coordinates instead of scrsize/2-30
6.movement of ghosts what is goin on in this part of the code ??

7.in movement of pacman method plz do explain what actually the code is doing
8.LevelInit method what is leveldat?
9.plz explain LevelContinue method
10.in checkmaze method y did he do

package pactut;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Event;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

import javax.swing.ImageIcon;
import javax.swing.JPanel;
import javax.swing.Timer;



public class Board extends JPanel implements ActionListener  {
    Dimension d;
    Font smallfont = new Font("Helvetica", Font.BOLD, 14);

    FontMetrics fmsmall, fmlarge;
    Image ii;
    Color dotcolor = new Color(192, 192, 0);
    Color mazecolor;

    boolean ingame = false;
    boolean dying = false;

    final int blocksize = 24;
    final int nrofblocks = 15;
    final int scrsize = nrofblocks * blocksize;
    final int pacanimdelay = 2;
    final int pacmananimcount = 4;
    final int maxghosts = 12;
    final int pacmanspeed = 6;

    int pacanimcount = pacanimdelay;
    int pacanimdir = 1;
    int pacmananimpos = 0;
    int nrofghosts = 6;
    int pacsleft, score;
    int deathcounter;
    int[] dx, dy;
    int[] ghostx, ghosty, ghostdx, ghostdy, ghostspeed;

    Image ghost;
    Image pacman1, pacman2up, pacman2left, pacman2right, pacman2down;
    Image pacman3up, pacman3down, pacman3left, pacman3right;
    Image pacman4up, pacman4down, pacman4left, pacman4right;

    int pacmanx, pacmany, pacmandx, pacmandy;
    int reqdx, reqdy, viewdx, viewdy;

    final short leveldata[] =
    { 19, 26, 26, 26, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 22,
      21, 0,  0,  0,  17, 16, 16, 16, 16, 16, 16, 16, 16, 16, 20,
      21, 0,  0,  0,  17, 16, 16, 16, 16, 16, 16, 16, 16, 16, 20, 
      21, 0,  0,  0,  17, 16, 16, 24, 16, 16, 16, 16, 16, 16, 20, 
      17, 18, 18, 18, 16, 16, 20, 0,  17, 16, 16, 16, 16, 16, 20,
      17, 16, 16, 16, 16, 16, 20, 0,  17, 16, 16, 16, 16, 24, 20, 
      25, 16, 16, 16, 24, 24, 28, 0,  25, 24, 24, 16, 20, 0,  21, 
      1,  17, 16, 20, 0,  0,  0,  0,  0,  0,  0,  17, 20, 0,  21,
      1,  17, 16, 16, 18, 18, 22, 0,  19, 18, 18, 16, 20, 0,  21,
      1,  17, 16, 16, 16, 16, 20, 0,  17, 16, 16, 16, 20, 0,  21, 
      1,  17, 16, 16, 16, 16, 20, 0,  17, 16, 16, 16, 20, 0,  21,
      1,  17, 16, 16, 16, 16, 16, 18, 16, 16, 16, 16, 20, 0,  21,
      1,  17, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 20, 0,  21,
      1,  25, 24, 24, 24, 24, 24, 24, 24, 24, 16, 16, 16, 18, 20,
      9,  8,  8,  8,  8,  8,  8,  8,  8,  8,  25, 24, 24, 24, 28 };

    final int validspeeds[] = { 1, 2, 3, 4, 6, 8 };
    final int maxspeed = 6;

    int currentspeed = 3;
    short[] screendata;
    Timer timer;


    public Board() {

        GetImages();

        addKeyListener(new TAdapter());

        screendata = new short[nrofblocks * nrofblocks];
        mazecolor = new Color(5, 100, 5);
        setFocusable(true);

        d = new Dimension(400, 400);

        setBackground(Color.black);
        setDoubleBuffered(true);

        ghostx = new int[maxghosts];
        ghostdx = new int[maxghosts];
        ghosty = new int[maxghosts];
        ghostdy = new int[maxghosts];
        ghostspeed = new int[maxghosts];
        dx = new int[4];
        dy = new int[4];
        timer = new Timer(40, this);
        timer.start();
    }

    public void addNotify() {
        super.addNotify();
        GameInit();
    }


    public void DoAnim() {
        pacanimcount--;
        if (pacanimcount <= 0) {
            pacanimcount = pacanimdelay;
            pacmananimpos = pacmananimpos + pacanimdir;
            if (pacmananimpos == (pacmananimcount - 1) || pacmananimpos == 0)
                pacanimdir = -pacanimdir;
        }
    }


    public void PlayGame(Graphics2D g2d) {
        if (dying) {
            Death();
        } else {
            MovePacMan();
            DrawPacMan(g2d);
            moveGhosts(g2d);
            CheckMaze();
        }
    }


    public void ShowIntroScreen(Graphics2D g2d) {

        g2d.setColor(new Color(0, 32, 48));
        g2d.fillRect(50, scrsize / 2 - 30, scrsize - 100, 50);
        g2d.setColor(Color.white);
        g2d.drawRect(50, scrsize / 2 - 30, scrsize - 100, 50);

        String s = "Press s to start.";
        Font small = new Font("Helvetica", Font.BOLD, 14);
        FontMetrics metr = this.getFontMetrics(small);

        g2d.setColor(Color.white);
        g2d.setFont(small);
        g2d.drawString(s, (scrsize - metr.stringWidth(s)) / 2, scrsize / 2);
    }


    public void DrawScore(Graphics2D g) {
        int i;
        String s;

        g.setFont(smallfont);
        g.setColor(new Color(96, 128, 255));
        s = "Score: " + score;
        g.drawString(s, scrsize / 2 + 96, scrsize + 16);
        for (i = 0; i < pacsleft; i++) {
            g.drawImage(pacman3left, i * 28 + 8, scrsize + 1, this);
        }
    }


    public void CheckMaze() {
        short i = 0;
        boolean finished = true;

        while (i < nrofblocks * nrofblocks && finished) {
            if ((screendata[i] & 48) != 0)
                finished = false;
            i++;
        }

        if (finished) {
            score += 50;

            if (nrofghosts < maxghosts)
                nrofghosts++;
            if (currentspeed < maxspeed)
                currentspeed++;
            LevelInit();
        }
    }

    public void Death() {

        pacsleft--;
        if (pacsleft == 0)
            ingame = false;
        LevelContinue();
    }


    public void moveGhosts(Graphics2D g2d) {
        short i;
        int pos;
        int count;

        for (i = 0; i < nrofghosts; i++) {
            if (ghostx[i] % blocksize == 0 && ghosty[i] % blocksize == 0) {
                pos = ghostx[i] / blocksize + nrofblocks * (int)(ghosty[i] / blocksize);

                count = 0;
                if ((screendata[pos] & 1) == 0 && ghostdx[i] != 1) {
                    dx[count] = -1;
                    dy[count] = 0;
                    count++;
                }
                if ((screendata[pos] & 2) == 0 && ghostdy[i] != 1) {
                    dx[count] = 0;
                    dy[count] = -1;
                    count++;
                }
                if ((screendata[pos] & 4) == 0 && ghostdx[i] != -1) {
                    dx[count] = 1;
                    dy[count] = 0;
                    count++;
                }
                if ((screendata[pos] & 8) == 0 && ghostdy[i] != -1) {
                    dx[count] = 0;
                    dy[count] = 1;
                    count++;
                }

                if (count == 0) {
                    if ((screendata[pos] & 15) == 15) {
                        ghostdx[i] = 0;
                        ghostdy[i] = 0;
                    } else {
                        ghostdx[i] = -ghostdx[i];
                        ghostdy[i] = -ghostdy[i];
                    }
                } else {
                    count = (int)(Math.random() * count);
                    if (count > 3)
                        count = 3;
                    ghostdx[i] = dx[count];
                    ghostdy[i] = dy[count];
                }

            }
            ghostx[i] = ghostx[i] + (ghostdx[i] * ghostspeed[i]);
            ghosty[i] = ghosty[i] + (ghostdy[i] * ghostspeed[i]);
            DrawGhost(g2d, ghostx[i] + 1, ghosty[i] + 1);

            if (pacmanx > (ghostx[i] - 12) && pacmanx < (ghostx[i] + 12) &&
                pacmany > (ghosty[i] - 12) && pacmany < (ghosty[i] + 12) &&
                ingame) {

                dying = true;
                deathcounter = 64;

            }
        }
    }


    public void DrawGhost(Graphics2D g2d, int x, int y) {
        g2d.drawImage(ghost, x, y, this);
    }


    public void MovePacMan() {
        int pos;
        short ch;

        if (reqdx == -pacmandx && reqdy == -pacmandy) {
            pacmandx = reqdx;
            pacmandy = reqdy;
            viewdx = pacmandx;
            viewdy = pacmandy;
        }
        if (pacmanx % blocksize == 0 && pacmany % blocksize == 0) {
            pos =
 pacmanx / blocksize + nrofblocks * (int)(pacmany / blocksize);
            ch = screendata[pos];

            if ((ch & 16) != 0) {
                screendata[pos] = (short)(ch & 15);
                score++;
            }

            if (reqdx != 0 || reqdy != 0) {
                if (!((reqdx == -1 && reqdy == 0 && (ch & 1) != 0) ||
                      (reqdx == 1 && reqdy == 0 && (ch & 4) != 0) ||
                      (reqdx == 0 && reqdy == -1 && (ch & 2) != 0) ||
                      (reqdx == 0 && reqdy == 1 && (ch & 8) != 0))) {
                    pacmandx = reqdx;
                    pacmandy = reqdy;
                    viewdx = pacmandx;
                    viewdy = pacmandy;
                }
            }

            // Check for standstill
            if ((pacmandx == -1 && pacmandy == 0 && (ch & 1) != 0) ||
                (pacmandx == 1 && pacmandy == 0 && (ch & 4) != 0) ||
                (pacmandx == 0 && pacmandy == -1 && (ch & 2) != 0) ||
                (pacmandx == 0 && pacmandy == 1 && (ch & 8) != 0)) {
                pacmandx = 0;
                pacmandy = 0;
            }
        }
        pacmanx = pacmanx + pacmanspeed * pacmandx;
        pacmany = pacmany + pacmanspeed * pacmandy;
    }


    public void DrawPacMan(Graphics2D g2d) {
        if (viewdx == -1)
            DrawPacManLeft(g2d);
        else if (viewdx == 1)
            DrawPacManRight(g2d);
        else if (viewdy == -1)
            DrawPacManUp(g2d);
        else
            DrawPacManDown(g2d);
    }

    public void DrawPacManUp(Graphics2D g2d) {
        switch (pacmananimpos) {
        case 1:
            g2d.drawImage(pacman2up, pacmanx + 1, pacmany + 1, this);
            break;
        case 2:
            g2d.drawImage(pacman3up, pacmanx + 1, pacmany + 1, this);
            break;
        case 3:
            g2d.drawImage(pacman4up, pacmanx + 1, pacmany + 1, this);
            break;
        default:
            g2d.drawImage(pacman1, pacmanx + 1, pacmany + 1, this);
            break;
        }
    }


    public void DrawPacManDown(Graphics2D g2d) {
        switch (pacmananimpos) {
        case 1:
            g2d.drawImage(pacman2down, pacmanx + 1, pacmany + 1, this);
            break;
        case 2:
            g2d.drawImage(pacman3down, pacmanx + 1, pacmany + 1, this);
            break;
        case 3:
            g2d.drawImage(pacman4down, pacmanx + 1, pacmany + 1, this);
            break;
        default:
            g2d.drawImage(pacman1, pacmanx + 1, pacmany + 1, this);
            break;
        }
    }


    public void DrawPacManLeft(Graphics2D g2d) {
        switch (pacmananimpos) {
        case 1:
            g2d.drawImage(pacman2left, pacmanx + 1, pacmany + 1, this);
            break;
        case 2:
            g2d.drawImage(pacman3left, pacmanx + 1, pacmany + 1, this);
            break;
        case 3:
            g2d.drawImage(pacman4left, pacmanx + 1, pacmany + 1, this);
            break;
        default:
            g2d.drawImage(pacman1, pacmanx + 1, pacmany + 1, this);
            break;
        }
    }


    public void DrawPacManRight(Graphics2D g2d) {
        switch (pacmananimpos) {
        case 1:
            g2d.drawImage(pacman2right, pacmanx + 1, pacmany + 1, this);
            break;
        case 2:
            g2d.drawImage(pacman3right, pacmanx + 1, pacmany + 1, this);
            break;
        case 3:
            g2d.drawImage(pacman4right, pacmanx + 1, pacmany + 1, this);
            break;
        default:
            g2d.drawImage(pacman1, pacmanx + 1, pacmany + 1, this);
            break;
        }
    }


    public void DrawMaze(Graphics2D g2d) {
        short i = 0;
        int x, y;

        for (y = 0; y < scrsize; y += blocksize) {
            for (x = 0; x < scrsize; x += blocksize) {
                g2d.setColor(mazecolor);
                g2d.setStroke(new BasicStroke(2));

                if ((screendata[i] & 1) != 0) // draws left
                {
                    g2d.drawLine(x, y, x, y + blocksize - 1);
                }
                if ((screendata[i] & 2) != 0) // draws top
                {
                    g2d.drawLine(x, y, x + blocksize - 1, y);
                }
                if ((screendata[i] & 4) != 0) // draws right
                {
                    g2d.drawLine(x + blocksize - 1, y, x + blocksize - 1,
                                 y + blocksize - 1);
                }
                if ((screendata[i] & 8) != 0) // draws bottom
                {
                    g2d.drawLine(x, y + blocksize - 1, x + blocksize - 1,
                                 y + blocksize - 1);
                }
                if ((screendata[i] & 16) != 0) // draws point
                {
                    g2d.setColor(dotcolor);
                    g2d.fillRect(x + 11, y + 11, 2, 2);
                }
                i++;
            }
        }
    }

    public void GameInit() {
        pacsleft = 3;
        score = 0;
        LevelInit();
        nrofghosts = 6;
        currentspeed = 3;
    }


    public void LevelInit() {
        int i;
        for (i = 0; i < nrofblocks * nrofblocks; i++)
            screendata[i] = leveldata[i];

        LevelContinue();
    }


    public void LevelContinue() {
        short i;
        int dx = 1;
        int random;

        for (i = 0; i < nrofghosts; i++) {
            ghosty[i] = 4 * blocksize;
            ghostx[i] = 4 * blocksize;
            ghostdy[i] = 0;
            ghostdx[i] = dx;
            dx = -dx;
            random = (int)(Math.random() * (currentspeed + 1));
            if (random > currentspeed)
                random = currentspeed;
            ghostspeed[i] = validspeeds[random];
        }

        pacmanx = 7 * blocksize;
        pacmany = 11 * blocksize;
        pacmandx = 0;
        pacmandy = 0;
        reqdx = 0;
        reqdy = 0;
        viewdx = -1;
        viewdy = 0;
        dying = false;
    }

    public void GetImages()
    {

      ghost = new ImageIcon("ghost.png").getImage();
      pacman1 = new ImageIcon("pacman.png").getImage();
      pacman2up = new ImageIcon("up1.png").getImage();
      pacman3up = new ImageIcon("up2.png").getImage();
      pacman4up = new ImageIcon("up3.png").getImage();
      pacman2down = new ImageIcon("down1.png").getImage();
      pacman3down = new ImageIcon("down2.png").getImage(); 
      pacman4down = new ImageIcon("down3.png").getImage();
      pacman2left = new ImageIcon("left1.png").getImage();
      pacman3left = new ImageIcon("left2.png").getImage();
      pacman4left = new ImageIcon("left3.png").getImage();
      pacman2right = new ImageIcon("right1.png").getImage();
      pacman3right = new ImageIcon("right2.png").getImage();
      pacman4right = new ImageIcon("right3.png").getImage();

    }

    public void paint(Graphics g)
    {
      super.paint(g);

      Graphics2D g2d = (Graphics2D) g;

      g2d.setColor(Color.black);
      g2d.fillRect(0, 0, d.width, d.height);

      DrawMaze(g2d);
      DrawScore(g2d);
      DoAnim();
      if (ingame)
        PlayGame(g2d);
      else
        ShowIntroScreen(g2d);

      g.drawImage(ii, 5, 5, this);
      Toolkit.getDefaultToolkit().sync();
      g.dispose();
    }

    class TAdapter extends KeyAdapter {
        public void keyPressed(KeyEvent e) {

          int key = e.getKeyCode();

          if (ingame)
          {
            if (key == KeyEvent.VK_LEFT)
            {
              reqdx=-1;
              reqdy=0;
            }
            else if (key == KeyEvent.VK_RIGHT)
            {
              reqdx=1;
              reqdy=0;
            }
            else if (key == KeyEvent.VK_UP)
            {
              reqdx=0;
              reqdy=-1;
            }
            else if (key == KeyEvent.VK_DOWN)
            {
              reqdx=0;
              reqdy=1;
            }
            else if (key == KeyEvent.VK_ESCAPE && timer.isRunning())
            {
              ingame=false;
            }
            else if (key == KeyEvent.VK_PAUSE) {
                if (timer.isRunning())
                    timer.stop();
                else timer.start();
            }
          }
          else
          {
            if (key == 's' || key == 'S')
          {
              ingame=true;
              GameInit();
            }
          }
      }

          public void keyReleased(KeyEvent e) {
              int key = e.getKeyCode();

              if (key == Event.LEFT || key == Event.RIGHT || 
                 key == Event.UP ||  key == Event.DOWN)
              {
                reqdx=0;
                reqdy=0;
              }
          }
      }

    public void actionPerformed(ActionEvent e) {
        repaint();  
    }


}

you don't need to know Java Game Programming in order to understand what variables do. are you familiar with Java programming?

first learn the basics. and trust me, you won't learn anything by copy-pasting some code and looking at it. start at the beginning, and just work your way up to more advanced stuff.

can u explain this part y r we performing bit and operation with 48

while (i < nrofblocks * nrofblocks && finished) {
            if ((screendata[i] & 48) != 0)
                finished = false;
            i++;
        }

tarareddy: Many of our members have English as their second or third language, hence the DaniWeb Community Rules:

Do post in full-sentence English
Do not write in all uppercase or use "leet", "txt" or "chatroom" speak

... so less of the text speak please.

Anyway, the code you are trying to learn from is a very poor example. It's badly designed and badly coded. Probably it's an early attempt by someone who was just starting to learn Java.
Stultuske is exactly right. All you will learn from studing this program is how to code like a beginner. Throw it away, and use the excellent tutorials on Oracle's web site to learn some proper Java.

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