Who uses Java BlueJ here? :)

[zak]

Has anyone read the book "objects first with Java; A practical introduction using blueJ"?

I am currently stuck on exercise 7.30 in the book. If anyone can help me out, then you will be handsomely rewarded.

[landshark]

Has anyone read the book "objects first with Java; A practical introduction using blueJ"?

I am currently stuck on exercise 7.30 in the book. If anyone can help me out, then you will be handsomely rewarded.

post the problem.

[zak]

sorry about that


Exercise 7.31 Implement an extension that allows a player to pick up one single item. This includes implementing two new commands: take and drop.

Exercise 7.31 Extend your implementation to allow the player to carry any numberof items.

Exercise 7.32 Add a restriction that allows the player to carry items only up to aspecified maximum weight. The maximum weight a player can carry is an attribute ofthe player.

Exercise 7.33 Implement an items command that prints out all items currently car-ried and their total weight.

Exercise 7.34 Add a magic cookie item to a room. Add an eat cookie command.If a player finds and eats the magic cookie, it increases the weight that the player cancarry. (You might like to modify this slightly to better fit into your own game scenario.)

[zak]

here is the project window:

[zak]

game class:



public class Game
{
private Parser parser;
private Room currentRoom;

/**
* Create the game and initialise its internal map.
*/
public Game()
{
createRooms();
parser = new Parser();
}

/**
* Create all the rooms and link their exits together.
*/
private void createRooms()
{
Room outside, theatre, pub, lab, office;

// create the rooms
outside = new Room("outside the main entrance of the university");
theatre = new Room("in a lecture theatre");
pub = new Room("in the campus pub");
lab = new Room("in a computing lab");
office = new Room("in the computing admin office");

// initialise room exits
outside.setExit("east", theatre);
outside.setExit("south", lab);
outside.setExit("west", pub);

theatre.setExit("west", outside);

pub.setExit("east", outside);

lab.setExit("north", outside);
lab.setExit("east", office);

office.setExit("west", lab);

currentRoom = outside; // start game outside
}

/**
* Main play routine. Loops until end of play.
*/
public void play()
{
printWelcome();

// Enter the main command loop. Here we repeatedly read commands and
// execute them until the game is over.

boolean finished = false;
while (! finished) {
Command command = parser.getCommand();
finished = processCommand(command);
}
System.out.println("Thank you for playing. Good bye.");
}

/**
* Print out the opening message for the player.
*/
private void printWelcome()
{
System.out.println();
System.out.println("Welcome to the World of Zuul!");
System.out.println("World of Zuul is a new, incredibly boring adventure game.");
System.out.println("Type 'help' if you need help.");
System.out.println();
System.out.println(currentRoom.getLongDescription());
}

/**
* Given a command, process (that is: execute) the command.
* If this command ends the game, true is returned, otherwise false is
* returned.
*/
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("quit")) {
wantToQuit = quit(command);
}
return wantToQuit;
}

// implementations of user commands:

/**
* Print out some help information.
* Here we print some stupid, cryptic message and a list of the
* command words.
*/
private void printHelp()
{
System.out.println("You are lost. You are alone. You wander");
System.out.println("around at the university.");
System.out.println();
System.out.println("Your command words are:");
parser.showCommands();
}

/**
* Try to go to one direction. If there is an exit, enter the new
* room, otherwise print an error message.
*/
private void goRoom(Command command)
{
if(!command.hasSecondWord()) {
// if there is no second word, we don't know where to go...
System.out.println("Go where?");
return;
}

String direction = command.getSecondWord();

// Try to leave current room.
Room nextRoom = currentRoom.getExit(direction);

if (nextRoom == null)
System.out.println("There is no door!");
else {
currentRoom = nextRoom;
System.out.println(currentRoom.getLongDescription());
}
}

/**
* "Quit" was entered. Check the rest of the command to see
* whether we really quit the game. Return true, if this command
* quits the game, false otherwise.
*/
private boolean quit(Command command)
{
if(command.hasSecondWord()) {
System.out.println("Quit what?");
return false;
}
else
return true; // signal that we want to quit
}
}

[zak]

Room class:



public class Room
{
private String description;
private HashMap exits; // stores exits of this room.

/**
* Create a room described "description". Initially, it has no exits.
* "description" is something like "in a kitchen" or "in an open court
* yard".
*/
public Room(String description)
{
this.description = description;
exits = new HashMap();
}

/**
* Define an exit from this room.
*/
public void setExit(String direction, Room neighbor)
{
exits.put(direction, neighbor);
}

/**
* Return the description of the room (the one that was defined in the
* constructor).
*/
public String getShortDescription()
{
return description;
}

/**
* Return a long description of this room, in the form:
* You are in the kitchen.
* Exits: north west
*/
public String getLongDescription()
{
return "You are " + description + ".\n" + getExitString();
}

/**
* Return a string describing the room's exits, for example
* "Exits: north west".
*/
private String getExitString()
{
String returnString = "Exits:";
Set keys = exits.keySet();
for(Iterator iter = keys.iterator(); iter.hasNext(); )
returnString += " " + iter.next();
return returnString;
}

/**
* Return the room that is reached if we go from this room in direction
* "direction". If there is no room in that direction, return null.
*/
public Room getExit(String direction)
{
return (Room)exits.get(direction);
}
}

[zak]

Command class:



public class Command
{
private String commandWord;
private String secondWord;

/**
* Create a command object. First and second word must be supplied, but
* either one (or both) can be null. The command word should be null to
* indicate that this was a command that is not recognised by this game.
*/
public Command(String firstWord, String secondWord)
{
commandWord = firstWord;
this.secondWord = secondWord;
}

/**
* Return the command word (the first word) of this command. If the
* command was not understood, the result is null.
*/
public String getCommandWord()
{
return commandWord;
}

/**
* Return the second word of this command. Returns null if there was no
* second word.
*/
public String getSecondWord()
{
return secondWord;
}

/**
* Return true if this command was not understood.
*/
public boolean isUnknown()
{
return (commandWord == null);
}

/**
* Return true if the command has a second word.
*/
public boolean hasSecondWord()
{
return (secondWord != null);
}
}

[zak]

Parser class:



import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.StringTokenizer;



public class Parser
{

private CommandWords commands; // holds all valid command words

public Parser()
{
commands = new CommandWords();
}

public Command getCommand()
{
String inputLine = ""; // will hold the full input line
String word1;
String word2;

System.out.print("> "); // print prompt

BufferedReader reader =
new BufferedReader(new InputStreamReader(System.in));
try {
inputLine = reader.readLine();
}
catch(java.io.IOException exc) {
System.out.println ("There was an error during reading: "
+ exc.getMessage());
}

StringTokenizer tokenizer = new StringTokenizer(inputLine);

if(tokenizer.hasMoreTokens())
word1 = tokenizer.nextToken(); // get first word
else
word1 = null;
if(tokenizer.hasMoreTokens())
word2 = tokenizer.nextToken(); // get second word
else
word2 = null;

// note: we just ignore the rest of the input line.

// Now check whether this word is known. If so, create a command
// with it. If not, create a "null" command (for unknown command).

if(commands.isCommand(word1))
return new Command(word1, word2);
else
return new Command(null, word2);
}

/**
* Print out a list of valid command words.
*/
public void showCommands()
{
commands.showAll();
}
}

[zak]

command words class:




public class CommandWords
{
// a constant array that holds all valid command words
private static final String[] validCommands = {
"go", "quit", "help"
};

/**
* Constructor - initialise the command words.
*/
public CommandWords()
{
// nothing to do at the moment...
}

/**
* Check whether a given String is a valid command word.
* Return true if it is, false if it isn't.
*/
public boolean isCommand(String aString)
{
for(int i = 0; i < validCommands.length; i++) {
if(validCommands.equals(aString))
return true;
}
// if we get here, the string was not found in the commands
return false;
}

/*
* Print all valid commands to System.out.
*/
public void showAll()
{
for(int i = 0; i < validCommands.length; i++) {
System.out.print(validCommands + " ");
}
System.out.println();
}
}

[zak]

anyone?

[kemical]

I'm not sure what kind of answer you're wanting

I don't use java at all, but from these exercises it looks like you need functions and variables that can handle the following:

-being able to store item names or id's in some type of list or array, for what items are current "held" by the player.
-add a weight property to all items, ex: 20.0, 15.5, 5.0, etc.. the player would then have their own property "maxWeight = 100.0" or something.. and each time you try to add a new item to the array/list it checks to see if the total weight is greater than the max weight, if it is, you can't carry it.
-the item list command would just be a way to list objects in an array/list.. using a for loop or something, for i=0; i<%totalItems; i++ etc..
-the magic cookie would just change the maxWeight property, set it to 10000 or something, then have a timer which resets it back after a while.

[zak]

I'm not sure what kind of answer you're wanting

I don't use java at all, but from these exercises it looks like you need functions and variables that can handle the following:

-being able to store item names or id's in some type of list or array, for what items are current "held" by the player.
-add a weight property to all items, ex: 20.0, 15.5, 5.0, etc.. the player would then have their own property "maxWeight = 100.0" or something.. and each time you try to add a new item to the array/list it checks to see if the total weight is greater than the max weight, if it is, you can't carry it.
-the item list command would just be a way to list objects in an array/list.. using a for loop or something, for i=0; i<%totalItems; i++ etc..
-the magic cookie would just change the maxWeight property, set it to 10000 or something, then have a timer which resets it back after a while.

Thanks Kemical!