Sokoban project in Java

[chira.laura.9]

Hi everyone. I have to do a simple Sokoban game, but I am new in Java and I really don't know how to begin. If you can help me with some advices or tutorials I'll be very thankful.

[mvmalderen]

Where do you have problems with in specific?
I'd suggest you to perform a Google search on 'Sokoban', look at existing implementations, play a couple of them and see how it works.
Familiarize yourself with the rules of the game. Start coding, and when you encounter problems come back and ask for help.

[chira.laura.9]

Ok. Thank you:)

[bguild]

Of course what you really want is a 2D array to store the current state of the game, an x and y variable to store the current location of your little warehouse manager guy, a list of (x,y) target points for the boxes, a javax.swing.JPanel to draw everything, and a java.awt.event.KeyListener on that JPanel to allow the keyboard to control the warehouse worker. Once you have that, you are practically done except for the frills.

[chira.laura.9]

Here is a code for the Sobokan Board. I took it from http://zetcode.com/tutorials/javagamestutorial/sokoban/, and I made some changes.
I get an error:Exception in thread "main" java.lang.NullPointerException

package sokoban;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.util.ArrayList;

import javax.swing.JPanel;

@SuppressWarnings("serial")
public class Board extends JPanel
{

    private final int DISTANCE_BORDER_GAMEGRAPHICS = 30;
    private final int SPACE = 20;
    private final int LEFT_COLLISION = 1;
    private final int RIGHT_COLLISION = 2;
    private final int UP_COLLISION = 3;
    private final int DOWN_COLLISION = 4;

    private  ArrayList<Wall> Walls;
    private  ArrayList<Objective> Objectives;
    private  ArrayList<Box> Boxes;

     private Player soko;
     private int width = 0;
     private int height = 0;
     private boolean completed = false;

     private String level =
             "    ######\n"
           + "    ##** #\n"
           + "    ##$  #\n"
           + "  #### @ $##\n"
           + "  #########\n";


     public Board() {

            addKeyListener(new SokoAdapter());
            setFocusable(true);
            initiateGame();
        }

     public int getBoardWidth() {
            return this.width;
        }

     public int getBoardHeight() {
            return this.height;
        }

     public final void initiateGame() {

            int x = DISTANCE_BORDER_GAMEGRAPHICS;
            int y = DISTANCE_BORDER_GAMEGRAPHICS;

            Wall wall;
            Box box;
            Objective objective;


            for (int i = 0; i < level.length(); i++) {

                char item = level.charAt(i);

                if (item == '\n') {
                    y += SPACE;
                    if (this.width < x) {
                        this.width = x;
                    }
                    x = DISTANCE_BORDER_GAMEGRAPHICS;
                } else if (item == '#') {
                    wall = new Wall(x, y);
                    Walls.add(wall);
                    x += SPACE;
                } else if (item == '$') {
                    box = new Box(x, y);
                    Boxes.add(box);
                    x += SPACE;
                } else if (item == '*') {
                    objective = new Objective(x, y);
                    Objectives.add(objective);
                    x += SPACE;
                } else if (item == '@') {
                    soko = new Player(x, y);
                    x += SPACE;
                } else if (item == ' ') {
                    x += SPACE;
                }

                height = y;
            }
        }

     public void buildGame(Graphics g) {

            g.setColor(new Color(250, 240, 170));
            g.fillRect(0, 0, this.getWidth(), this.getHeight());

            ArrayList world = new ArrayList();
            world.addAll(Walls);
            world.addAll(Objectives);
            world.addAll(Boxes);
            world.add(soko);

            for (int i = 0; i < world.size(); i++) {

                Actor item = (Actor) world.get(i);

                if ((item instanceof Player)
                        || (item instanceof Box)) {
                    g.drawImage(item.getImage(), item.x() + 2, item.y() + 2, this);
                } else {
                    g.drawImage(item.getImage(), item.x(), item.y(), this);
                }

                if (completed) {
                    g.setColor(new Color(0, 0, 0));
                    g.drawString("Completed", 25, 20);
                }

            }
        }

     @Override
        public void paint(Graphics g) {
            super.paint(g);
            buildGame(g);
        }

        class SokoAdapter extends KeyAdapter {

            @Override
            public void keyPressed(KeyEvent e) {

                if (completed) {
                    return;
                }


                int key = e.getKeyCode();


                if (key == KeyEvent.VK_LEFT) {
                    if (checkWallCollision(soko, LEFT_COLLISION)) {
                        return;
                    }

                    if (checkBoxCollision(LEFT_COLLISION)) {
                        return;
                    }

                    soko.move(-SPACE, 0);

                } else if (key == KeyEvent.VK_RIGHT) {

                    if (checkWallCollision(soko,
                            RIGHT_COLLISION)) {
                        return;
                    }

                    if (checkBoxCollision(RIGHT_COLLISION)) {
                        return;
                    }

                    soko.move(SPACE, 0);

                } else if (key == KeyEvent.VK_UP) {

                    if (checkWallCollision(soko,
                            UP_COLLISION)) {
                        return;
                    }

                    if (checkBoxCollision(UP_COLLISION)) {
                        return;
                    }

                    soko.move(0, -SPACE);

                } else if (key == KeyEvent.VK_DOWN) {

                    if (checkWallCollision(soko,
                            DOWN_COLLISION)) {
                        return;
                    }

                    if (checkBoxCollision(DOWN_COLLISION)) {
                        return;
                    }

                    soko.move(0, SPACE);

                } else if (key == KeyEvent.VK_R) {
                    restartLevel();
                }

                repaint();
            }
        }

        private boolean checkWallCollision(Actor actor, int type) {

            if (type == LEFT_COLLISION) {

                for (int i = 0; i < Walls.size(); i++) {
                    Wall wall = (Wall) Walls.get(i);
                    if (actor.isLeftCollision(wall)) {
                        return true;
                    }
                }
                return false;

            } else if (type == RIGHT_COLLISION) {

                for (int i = 0; i < Walls.size(); i++) {
                    Wall wall = (Wall) Walls.get(i);
                    if (actor.isRightCollision(wall)) {
                        return true;
                    }
                }
                return false;

            } else if (type == UP_COLLISION) {

                for (int i = 0; i < Walls.size(); i++) {
                    Wall wall = (Wall) Walls.get(i);
                    if (actor.isTopCollision(wall)) {
                        return true;
                    }
                }
                return false;

            } else if (type == DOWN_COLLISION) {

                for (int i = 0; i < Walls.size(); i++) {
                    Wall wall = (Wall) Walls.get(i);
                    if (actor.isBottomCollision(wall)) {
                        return true;
                    }
                }
                return false;
            }
            return false;
        }

        private boolean checkBoxCollision(int type) {

            if (type == LEFT_COLLISION) {

                for (int i = 0; i < Boxes.size(); i++) {

                    Box box = (Box) Boxes.get(i);
                    if (soko.isLeftCollision(box)) {

                        for (int j=0; j < Boxes.size(); j++) {
                            Box item = (Box) Boxes.get(j);
                            if (!box.equals(item)) {
                                if (box.isLeftCollision(item)) {
                                    return true;
                                }
                            }
                            if (checkWallCollision(box,
                                    LEFT_COLLISION)) {
                                return true;
                            }
                        }
                        box.move(-SPACE, 0);
                        isCompleted();
                    }
                }
                return false;

            } else if (type == RIGHT_COLLISION) {

                for (int i = 0; i < Boxes.size(); i++) {

                    Box box = (Box) Boxes.get(i);
                    if (soko.isRightCollision(box)) {
                        for (int j=0; j < Boxes.size(); j++) {

                            Box item = (Box) Boxes.get(j);
                            if (!box.equals(item)) {
                                if (box.isRightCollision(item)) {
                                    return true;
                                }
                            }
                            if (checkWallCollision(box,
                                    RIGHT_COLLISION)) {
                                return true;
                            }
                        }
                        box.move(SPACE, 0);
                        isCompleted();                   
                    }
                }
                return false;

            } else if (type == UP_COLLISION) {

                for (int i = 0; i < Boxes.size(); i++) {

                    Box box = (Box) Boxes.get(i);
                    if (soko.isTopCollision(box)) {
                        for (int j = 0; j < Boxes.size(); j++) {

                            Box item = (Box) Boxes.get(j);
                            if (!box.equals(item)) {
                                if (box.isTopCollision(item)) {
                                    return true;
                                }
                            }
                            if (checkWallCollision(box,
                                    UP_COLLISION)) {
                                return true;
                            }
                        }
                        box.move(0, -SPACE);
                        isCompleted();
                    }
                }

                return false;

            } else if (type == DOWN_COLLISION) {

                for (int i = 0; i < Boxes.size(); i++) {

                    Box box = (Box) Boxes.get(i);
                    if (soko.isBottomCollision(box)) {
                        for (int j = 0; j < Boxes.size(); j++) {

                            Box item = (Box) Boxes.get(j);
                            if (!box.equals(item)) {
                                if (box.isBottomCollision(item)) {
                                    return true;
                                }
                            }
                            if (checkWallCollision(box,
                                    DOWN_COLLISION)) {
                                return true;
                            }
                        }
                        box.move(0, SPACE);
                        isCompleted();
                    }
                }
            }

            return false;
        }

        public void isCompleted() {

            int num = Boxes.size();
            int compl = 0;

            for (int i = 0; i < num; i++) {
                Box box = (Box) Boxes.get(i);
                for (int j = 0; j < num; j++) {
                    Objective Objective = (Objective) Objectives.get(j);
                    if (box.x() == Objective.x()
                            && box.y() == Objective.y()) {
                        compl += 1;
                    }
                }
            }

            if (compl == num) {
                completed = true;
                repaint();
            }
        }

        public void restartLevel() {

            Objectives.clear();
            Boxes.clear();
            Walls.clear();
            initiateGame();
            if (completed) {
                completed = false;
            }
        }
    } 

[bguild]

I suggest that you make one yourself from scratch. It's really a nice simple game that can be made from scratch without excessive effort. The way it is done above is certainly using excessive effort. Instead of using a 2D array to represent the board, it is using sprites and collision detection for no apparent reason. I would abandon that whole implementation of Sokoban and make something simpler if I were you.