Random Obstacle Avoidance Example

From the book ai for game developers. Random Obstacle Avoidance. The white block moves through the map and avoids the green trees. Below the code that shows how it is done.

 

import java.awt.*;
import java.applet.*;
public class RandomObstacleAvoidanceExample001 extends Applet implements Runnable{
 Graphics bufferGraphics;
    Image offscreen;
 int sx , sy , ex , ey; // start and end position
 int px , py; // player position
 long delay;
 private int map[][] =  new int[][]{
 {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
 {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
 {0,0,1,0,0,1,0,0,0,0,0,0,1,0,0,0,1,0,0,0},
 {0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0},
 {0,0,0,0,0,1,0,0,0,1,0,0,0,0,0,0,0,0,0,0},
 {0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,1,0,0,0},
 {0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0},
 {0,0,0,0,0,1,0,1,0,0,0,0,0,0,0,1,0,0,0,0},
 {0,0,0,1,0,0,0,0,0,0,0,1,0,1,0,0,0,1,0,0},
 {0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0},
 {0,0,1,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0},
 {0,0,0,0,0,0,0,0,0,0,1,0,0,0,1,0,0,1,0,0},
 {0,0,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0},
 {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
 {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
 };
 public void init(){
  setBackground( Color.black );
     offscreen = createImage(getSize().width,getSize().height);
     bufferGraphics = offscreen.getGraphics();
  setstartposition();
  setendposition();
  px = sx;
  py = sy;
  new Thread(this).start();
 }
    public void run() {
     for(;;) { // animation loop never ends
         moveplayer();
         repaint();
         try {
             Thread.sleep(16);
            }
             catch (InterruptedException e) {
             }
     }
    }
 public void update (Graphics g)
  {
  bufferGraphics.clearRect( 0 , 0 , getSize().width , getSize().height );
     bufferGraphics.setColor ( Color.white );
     bufferGraphics.drawString( "Random Obstacle Avoidance." , 10 , 10 );
  bufferGraphics.setColor( Color.green );
  // draw map
  for ( int y = 0 ; y < 15 ; y++ ){
   for ( int x = 0 ; x < 20 ; x++ ){
    if ( map[ y ][ x ] == 1 ){
     bufferGraphics.fillOval( x * 16 , y * 16 , 16 , 16 );
    }
   }
  }
  // draw end and start position
  bufferGraphics.setColor( Color.red );
  bufferGraphics.fillRect( sx * 16 , sy * 16 , 16 , 16 );
  bufferGraphics.setColor( Color.yellow );
  bufferGraphics.fillRect( ex * 16 , ey * 16 , 16 , 16 );
  // draw player
  bufferGraphics.setColor( Color.white );
  bufferGraphics.fillRect( px * 16 , py * 16 , 16 , 16 );

     g.drawImage(offscreen,0,0,this);

  }
  public void moveplayer(){
   if ( delay < System.currentTimeMillis() ){
    int newx = px;
    int newy = py;
    if ( px < ex ){
     newx++;
    }
    if ( px > ex ){
     newx--;
    }
    if ( py < ey ){
     newy++;
    }
    if ( py > ey ){
     newy--;
    }
    if ( map[ newy ][ newx ] == 1 ){
     boolean newposfound = false;
     newx = px;
     newy = py;
     while ( newposfound == false ){
      if ( (int)(Math.random() * 2 ) == 0 ){
       newx--;
      }else{
       newx++;
      }
      if ( (int)(Math.random() * 2 ) == 0 ){
       newy--;
      }else{
       newy++;
      }
      if ( map[ newy ][ newx ] == 0 ){
       newposfound = true;
      }
     }
    }
    px = newx;
    py = newy;
    if ( px == ex && py == ey ){
    setstartposition();
    setendposition();
    px = sx;
    py = sy;
    }
    delay = System.currentTimeMillis() + 200;
   }
  }
 public void setstartposition(){
  if (  (int)( Math.random() * 2 ) == 0 ){
   sx = ( int )( Math.random() * 6 );
   sy = 0;
  }else{
   sx = 0;
   sy = ( int )( Math.random() * 6 );
  }
 }
 public void setendposition(){
  if (  (int)( Math.random() * 2 ) == 0 ){
   ex = 20 - ( int )( Math.random() * 6 );
   ey = 14;
  }else{
   ex = 19;
   ey = 14 - ( int )( Math.random() * 6 );
  }

 }
}