Null Pointer Exception

[Martin vanPutten]

I have a nullpointerexception runtime error I can't figure out why. I have two classes... one with the print method... and the other thatpulls that method into a textarea... does anybody see any problem with this:

  public String printWelcome()
    {
        return "Welcome to the World of Zuul!";}  

  textArea.append(game.printWelcome());  

For further reference... heres the entire two classes:

  import java.util.*;
 
/**
 * Class Game - The game.
 * 
 * @author  Martin vanPutten
 * @version 2007.08.05
 */
 
public class Game 
{    
  public static void main(String args[])
{
Game game = new Game();
ViewManager frame = new ViewManager();

game.play();
}
  
    private Parser parser;
    private Player player;
    private People person;
    private Room currentRoom, prevRoom, outside, construction, chargeRoom, fireRoom;
    public String playerName;
    private Scanner reader = new Scanner(System.in);
    
    public Game() 
    {
        createRooms();
        parser = new Parser();
        prevRoom = currentRoom;
        chargeRoom = currentRoom;
        player = new Player(playerName, currentRoom, 40, 0);
        person = currentRoom.getPeople();
    }
 
    private void createRooms()
    {
        Room theatre, pub, lab, office, mainEntrance, hallway1, hallway2, hallway3, library;
      
        outside = new Room("outside the main entrance of the university", false);
        theatre = new Room("in a lecture theatre", false);
        pub = new Room("in the campus pub", false);
        lab = new Room("in a computing lab", false);
        office = new Room("in the computing admin office", false);
        mainEntrance = new Room("in the main entrance of university", false);
        hallway1 = new Room("in a hallway from office to theater", false);
        hallway2 = new Room("in a hallway outside pub", false);
        hallway3 = new Room("in a hallway outside lab", false);
        library = new Room("in the library", false);
        construction = new Room("in construction... turn around. There is a chute. Type 'fall' to fall down the chute. \nYou cannot use the beamer here. There is no return to this room. \nThis room has an aurora around it. You don't worry about it right now", true);
                
        currentRoom = outside; 
        
        outside.setExit("east", theatre);
        outside.setExit("south", lab);
        outside.setExit("west", pub); 
        outside.setExit("north", mainEntrance); 
        mainEntrance.setExit("south", outside);
        mainEntrance.setExit("west", hallway1); 
        mainEntrance.setExit("northeast", hallway2);
        theatre.setExit("west", outside);
        theatre.setExit("south", office);
        theatre.setExit("southwest", lab);
        theatre.setExit("northwest", hallway2);
        pub.setExit("east", outside);
        pub.setExit("southeast", lab);
        pub.setExit("south", library);
        pub.setExit("northeast", hallway1);
        hallway1.setExit("southwest", pub);
        hallway1.setExit("east", mainEntrance);
        hallway1.setExit("northwest", hallway3);
        hallway2.setExit("southwest", mainEntrance);
        hallway2.setExit("southeast", theatre);
        hallway3.setExit("southeast", hallway1);
        hallway3.setExit("northwest", construction);
        construction.setExit("southeast", hallway3);
        library.setExit("north", pub);
        library.setExit("east", lab);
        lab.setExit("north", outside);
        lab.setExit("east", office);
        lab.setExit("northeast", theatre);
        lab.setExit("northwest", pub);
        lab.setExit("west", library);
        office.setExit("west", lab);
        office.setExit("north", theatre);
        
        Item computer, flag, printer, book, ration, mouse, speakers, game, monitor, ring, key;
                
        computer = new Item(20, "Computer", "Alienware ALX Computer.");
        flag = new Item(5, "Flag", "Canada Flag.");
        printer = new Item(15, "Printer", "Canon Inkjet 530.");
        book = new Item(2, "Book", "The Lord Of The Rings.");
        ration = new Item(2, "Ration", "Hamburger.");
        mouse = new Item(1, "Mouse", "Logitech G7 Mouse.");
        speakers = new Item(4, "Speakers", "Logitech x540.");
        game = new Item(1, "PC Game", "Prince Of Persia game.");
        monitor = new Item(15, "Monitor", "Viewsonic Monitor");
        ring = new Item(1, "Ring", "Woodstock High School Graduate Ring.");
        key = new Item(1, "Key", "This key opens a locked door.");
        
        lab.setItem("computer", computer);
        lab.setItem("printer", printer);
        lab.setItem("mouse", mouse);
        lab.setItem("speakers", speakers);
        lab.setItem("game", game);
        lab.setItem("monitor", monitor);
        outside.setItem("flag", flag);
        library.setItem("book", book);
        pub.setItem("ration", ration);
        theatre.setItem("ring", ring);
        office.setItem("key", key);      
        
        outside.setPeople("Pookie", "I am hungry.", "ration");
        lab.setPeople("Long Don Silver", "It is better to fade out than to fade away.", "ring");
        construction.setPeople("Guy", "You almost beat the game...", "key");
    }
    
    public void play() 
    {            
        printWelcome();
     
        boolean finished = false;
        while(! finished) 
        {
            Command command = parser.getCommand();
            finished = processCommand(command);
        }
        
        System.out.println("Thank you for playing. Good bye.");
    }
 
    public String printWelcome()
    {
        return "Welcome to the World of Zuul!";
        //System.out.println("World of Zuul is a new, incredible adventure game.");
        //System.out.println();
        //System.out.println("Type 'help' if you need help.");
        //System.out.println("You have a beamer to transport to rooms. \nType 'charge' to charge the beamer and 'fire' to transport.");
        //System.out.println("You can only lift a total of 40 pounds. You will have to drop items to pick others up.");
        //System.out.println();
        //return printDetails();
    }
    
    public void printDetails()
    {
    System.out.println(currentRoom.getLongDescription());
        System.out.println(currentRoom.getItemDescription());
        System.out.println(currentRoom.getPeopleDescription());
    }
 
    private boolean processCommand(Command command) 
    {
        boolean wantToQuit = false;
 
        if(command.isUnknown()) 
        {
            System.out.println("I don't know what you mean...");
            return false;
        }
 
        String commandWord = command.getCommandWord();
        if(commandWord.equals("help")) 
            printHelp();
        else if(commandWord.equals("go")) 
            goRoom(command);
        else if(commandWord.equals("take")) 
            takeItem(command);
        else if(commandWord.equals("drop")) 
            dropItem(command);
        else if(commandWord.equals("give"))
        giveItem(command);
        else if(commandWord.equals("items"))
        getItems(command);
        else if(commandWord.equals("back"))
        back(command);
        else if(commandWord.equals("fall"))
        fall(command);
        else if(commandWord.equals("charge"))
        chargeBeamer(command);
        else if(commandWord.equals("fire"))
       fireBeamer(command);
               
        return wantToQuit;
    }
 
    private void printHelp() 
    {
        System.out.println("You are lost. You are alone. You wander around at the university.");
        System.out.println();
        System.out.println("Your command words are:");
        parser.showCommands();
    }
 
    private void goRoom(Command command) 
    {
        if(!command.hasSecondWord()) 
            System.out.println("Go where?");
 
        String direction = command.getSecondWord();
 
        Room nextRoom = currentRoom.getExit(direction);
 
        if(nextRoom == null)
            System.out.println("There is no door!");
        else 
        {
        if(nextRoom.isLocked() == true)
        {
        if(player.hasKey() == true)
        {
prevRoom = currentRoom;
    currentRoom = nextRoom;
    person = currentRoom.getPeople();
        printDetails();
        }
        else
        System.out.println("You need a key to enter this room.");
        }
        else
        {
prevRoom = currentRoom;
    currentRoom = nextRoom;
    person = currentRoom.getPeople();
        printDetails();
        }
        }
    }
    
    public void back(Command command)
    {
    if(command.hasSecondWord())
        System.out.println("Please type 'back' to go back.");
    else
        goBack();
    }
    
    public void getItems(Command command)
    {
    if(command.hasSecondWord())
        System.out.println("Please type 'items' to access your inventory.");
        else
        System.out.println(player.playersInventory(command.getSecondWord()));
    }
    
    public void takeItem(Command command) 
    {    
        if(!command.hasSecondWord()) 
            System.out.println("Take what?");
 
        String itemName = command.getSecondWord();
 
        Item items = currentRoom.getItem(itemName);
        
        if(items == null) 
            System.out.println("You do not have that item!");
        else
        {  
        if(player.getCurrentWeight() >= player.getMaxWeight())
        System.out.println("You cannot pick up any more items. Drop some first.");
        else if((player.getCurrentWeight() + items.getWeight()) <= player.getMaxWeight())
        {
        player.putItem(itemName, items);
        System.out.println("You picked up a " + itemName);
        
        player.setCurrentWeight(player.getCurrentWeight() + items.getWeight());
        
        currentRoom.removeItem(itemName);
        }
        else
        System.out.println("You cannot pick up any more items. Drop some first.");
        }
    }
    
    public void giveItem(Command command)
    {
    if(!command.hasSecondWord())
    System.out.println("Give what?");
    
    String itemName = command.getSecondWord();
    
        Item items = player.getItem(itemName); 
    
    if(items == null)
System.out.println("You do not have that item.");
else if(itemName.equals(person.getItem()))
{
        System.out.println("You have givin a " + itemName + " to " + person.getName());
        player.setCurrentWeight(player.getCurrentWeight() - items.getWeight());
        player.removeItem(itemName);
        
        peopleTalk();
}
else
System.out.println("You cannot give this item to this person.");
    }
    
    public void dropItem(Command command) 
    {    
        if(!command.hasSecondWord())
            System.out.println("Drop what?");
 
        String itemName = command.getSecondWord();
 
        Item items = player.getItem(itemName); 
        
        if(items == null)
        System.out.println("You have no items!");
        else
        {
        currentRoom.putItem(itemName, items);
        System.out.println("You have dropped a " + itemName);
        
        player.setCurrentWeight(player.getCurrentWeight() - items.getWeight());
        player.removeItem(itemName);
        }
    }
    
    public void fall(Command command)
    {
    if(currentRoom == construction)
        {
        if(command.hasSecondWord())
        System.out.println("Please type 'fall'. Should you really do this?");
        else
        fallDownChute();
        }
        else
        System.out.println("What are you talking about?");
    }
    
    public void chargeBeamer(Command command)
    {
    if(command.hasSecondWord())
        System.out.println("You only have to type 'charge' to charge the beamer.");
    else
    {
        chargeRoom = currentRoom;
        System.out.println("The beamer has been charged.");
    }       
    }
    
    public void fireBeamer(Command command)
    {
    if(command.hasSecondWord())
        System.out.println("You only have to type 'fire' to fire the beamer.");
    else if(!prevRoom.equals(currentRoom))
    {
    currentRoom = chargeRoom;
    printDetails();
    }
    }
    
    private void goBack()
    {
    if(!prevRoom.equals(currentRoom))
    {
    currentRoom = prevRoom;
    person = currentRoom.getPeople();
    printDetails();
    }
    else
    System.out.println("You cannot go back any farther.");
    }
    
    private void fallDownChute()
    {
    currentRoom = outside;
    prevRoom = currentRoom;
    person = currentRoom.getPeople();
        printDetails();
    }
    
    private void peopleTalk()
    {
    if(person.getName() == "Pookie")
        System.out.println("I dropped a key somewhere. But I can't remember where? By the way, this food is good.");
        if(person.getName() == "Long Don Silver")
        System.out.println("I saw something shiny but I had to use the washroom! Couldn't pick it up! Arrghh. Thanks for the ring though!");
        if(person.getName() == "Guy")
        System.out.println("Congratulations, you have won the game! Please continue to explore Zuul!");
    }
}
 
  

  import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
 
/**
 * Class ViewPanel - Manages the panels in the frame.
 * 
 * @author  Martin vanPutten
 * @version 2007.04.05
 */
 
public class ViewPanel extends JPanel
{
private Game game;
 
public ViewPanel(Container pane)
{
pane.setLayout(null);

JLabel titleLabel = new JLabel("ZUUL");
titleLabel.setFont(new Font("Comic Sans", Font.BOLD, 70));
JLabel authorLabel = new JLabel("By: Martin vanPutten");
authorLabel.setFont(new Font("Comic Sans", Font.PLAIN, 24));
JLabel goLabel = new JLabel("...Go...");
goLabel.setFont(new Font("Comic Sans", Font.PLAIN, 18));

JButton northButton = new JButton("North");
JButton eastButton = new JButton("East");
JButton southButton = new JButton("South");
JButton westButton = new JButton("West");
JButton northeastButton = new JButton("Northeast");
JButton northwestButton = new JButton("Northwest");
JButton southeastButton = new JButton("Southeast");
JButton southwestButton = new JButton("Southwest");
JButton takeButton = new JButton("Take");
JButton dropButton = new JButton("Drop");
JButton giveButton = new JButton("Give");
JButton backButton = new JButton("Back");
JButton chargeButton = new JButton("Charge");
JButton fireButton = new JButton("Fire");
JButton itemsButton = new JButton("Items");
JButton helpButton = new JButton("Help");
JButton fallButton = new JButton("Fall");
JButton quitButton = new JButton("Quit");

ImageIcon picture = new ImageIcon("images/outside.jpg");
JLabel map = new JLabel(picture, JLabel.CENTER);

JTextArea textArea = new JTextArea();
textArea.setEditable(false);
        textArea.setRows(17);
        textArea.setColumns(29);
        textArea.setLineWrap(true);
    textArea.setWrapStyleWord(true);
        
pane.add(titleLabel);
pane.add(authorLabel);
pane.add(goLabel);
pane.add(northButton);
pane.add(eastButton);
pane.add(southButton);
pane.add(westButton);
pane.add(northeastButton);
pane.add(northwestButton);
pane.add(southeastButton);
pane.add(southwestButton);
pane.add(map);
pane.add(textArea);
pane.add(takeButton);
pane.add(dropButton);
pane.add(giveButton);
pane.add(backButton);
pane.add(chargeButton);
pane.add(fireButton);
pane.add(itemsButton);
pane.add(helpButton);
pane.add(fallButton);
pane.add(quitButton);

Insets insets = pane.getInsets();
Dimension size;

size = titleLabel.getPreferredSize();
titleLabel.setBounds(45 + insets.left, 7 + insets.top, size.width, size.height);
size = authorLabel.getPreferredSize();
authorLabel.setBounds(75 + insets.left, 90 + insets.top, size.width, size.height);
size = goLabel.getPreferredSize();
goLabel.setBounds(523 + insets.left, 85 + insets.top, size.width, size.height);
size = northButton.getPreferredSize();
northButton.setBounds(500 + insets.left, 50 + insets.top, 100, size.height);
size = eastButton.getPreferredSize();
eastButton.setBounds(610 + insets.left, 85 + insets.top, 100, size.height);
size = southButton.getPreferredSize();
southButton.setBounds(500 + insets.left, 120 + insets.top, 100, size.height);
size = westButton.getPreferredSize();
westButton.setBounds(390 + insets.left, 85 + insets.top, 100, size.height);
size = northeastButton.getPreferredSize();
northeastButton.setBounds(610 + insets.left, 50 + insets.top, 100, size.height);
size = northwestButton.getPreferredSize();
northwestButton.setBounds(390 + insets.left, 50 + insets.top, 100, size.height);
size = southeastButton.getPreferredSize();
southeastButton.setBounds(610 + insets.left, 120 + insets.top, 100, size.height);
size = southwestButton.getPreferredSize();
southwestButton.setBounds(390 + insets.left, 120 + insets.top, 100, size.height);
map.setBounds(75 + insets.left, 170 + insets.top, 275, 272);
size = textArea.getPreferredSize();
textArea.setBounds(390 + insets.left, 170 + insets.top, size.width, size.height);
size = takeButton.getPreferredSize();
takeButton.setBounds(120 + insets.left, 465 + insets.top, 100, size.height);
size = dropButton.getPreferredSize();
dropButton.setBounds(120 + insets.left, 500 + insets.top, 100, size.height);
size = giveButton.getPreferredSize();
giveButton.setBounds(230 + insets.left, 465 + insets.top, 100, size.height);
size = backButton.getPreferredSize();
backButton.setBounds(230 + insets.left, 500 + insets.top, 100, size.height);
size = chargeButton.getPreferredSize();
chargeButton.setBounds(340 + insets.left, 465 + insets.top, 100, size.height);
size = fireButton.getPreferredSize();
fireButton.setBounds(340 + insets.left, 500 + insets.top, 100, size.height);
size = itemsButton.getPreferredSize();
itemsButton.setBounds(450 + insets.left, 465 + insets.top, 100, size.height);
size = helpButton.getPreferredSize();
helpButton.setBounds(450 + insets.left, 500 + insets.top, 100, size.height);
size = fallButton.getPreferredSize();
fallButton.setBounds(560 + insets.left, 465 + insets.top, 100, size.height);
size = quitButton.getPreferredSize();
quitButton.setBounds(560 + insets.left, 500 + insets.top, 100, size.height);

textArea.append(game.printWelcome());

quitButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
System.exit(0);
} 
}
);
}
}  

[Michael Dunn]

    
public class ViewPanel extends JPanel
{
private Game game;//<-----------------------

[Martin vanPutten]

Don't I have to call the Game class in order to get the printWelcome method?

[Michael Dunn]

yes, but nowhere in ViewPanel do you create an instance of 'Game'.

you probably want to pass a reference to the game object you create in main(),
via ViewPanel's constructor

[Martin vanPutten]

I can't believe I forgot to do that... its always the little things! Thanks!