Chapter06 designing class-zuul bad

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zuul-bad
/**
* This class is the main class of the "World of Zuul"
application.
* "World of Zuul" is a very simple, text based
adventure game.
*
* This class holds information about a command that
was issued by the user.
* A command currently consists of two strings: a
command word and a second
* word (for example, if the command was "take map",
then the two strings
* obviously are "take" and "map").
*
* The way this is used is: Commands are already
checked for being valid
* command words. If the user entered an invalid
command (a word that is not
* known) then the command word is <null>.
*
* If the command had only one word, then the second
word is <null>.
*
* @author Michael Kolling and David J. Barnes
* @version 1.0 (February 2002)
*/
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);
}
}

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/*
application.
adventure game.
*
* This class holds an enumeration of all command words
known to the game.
* It is used to recognise commands as they are typed
in.
*
*/
class CommandWords
{
// a constant array that holds all valid command
words
private static final String validCommands[] = {
"go", "quit", "help", "look"
};
/**
* 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[i].equals(aString))
return true;
}
// if we get here, the string was not found in
the commands
return false;
}
}

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/**
application.
adventure game. Users
* can walk around some scenery. That's all. It should
really be extended
* to make it more interesting!
*
* To play this game, create an instance of this class
and call the "play"
* method.
*
* This main class creates and initialises all the
others: it creates all
* rooms, creates the parser and starts the game. It
also evaluates and
* executes the commands that the parser returns.
*
*/
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.setExits(null, theatre, lab, pub);
theatre.setExits(null, null, null, outside);
pub.setExits(null, outside, null, null);
lab.setExits(outside, office, null, null);
office.setExits(null, null, null, 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();

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System.out.println("Welcome to Adventure!");
System.out.println("Adventure is a new,
incredibly boring adventure game.");
System.out.println("Type 'help' if you need
help.");
System.out.println("You are " +
currentRoom.getDescription());
System.out.print("Exits: ");
if(currentRoom.northExit != null)
System.out.print("north ");
if(currentRoom.eastExit != null)
System.out.print("east ");
if(currentRoom.southExit != null)
System.out.print("south ");
if(currentRoom.westExit != null)
System.out.print("west ");
}
/**
* 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("Your command words are:");
System.out.println(" go quit help");
}
/**
* 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 = null;
if(direction.equals("north"))
nextRoom = currentRoom.northExit;
if(direction.equals("east"))
nextRoom = currentRoom.eastExit;
if(direction.equals("south"))

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nextRoom = currentRoom.southExit;
if(direction.equals("west"))
nextRoom = currentRoom.westExit;
if (nextRoom == null)
System.out.println("There is no door!");
else {
currentRoom = nextRoom;
System.out.println("You are " +
currentRoom.getDescription());
System.out.print("Exits: ");
if(currentRoom.northExit != null)
System.out.print("north ");
if(currentRoom.eastExit != null)
System.out.print("east ");
if(currentRoom.southExit != null)
System.out.print("south ");
if(currentRoom.westExit != null)
System.out.print("west ");
}
}
/**
* "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
}
}

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import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
/*
application.
adventure game.
*
* This parser reads user input and tries to interpret
it as an "Adventure"
* command. Every time it is called it reads a line
from the terminal and
* tries to interpret the line as a two word command.
It returns the command
* as an object of class Command.
*
* The parser has a set of known command words. It
checks user input against
* the known commands, and if the input is not one of
the known commands, it
* returns a command object that is marked as an
unknown command.
*
*/
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);
}
}

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/*
* Class Room - a room in an adventure game.
*
application.
adventure game.
*
* A "Room" represents one location in the scenery of
the game. It is
* connected to other rooms via exits. The exits are
labelled north,
* east, south, west. For each direction, the room
stores a reference
* to the neighboring room, or null if there is no exit
in that direction.
*
*/
class Room
{
public String description;
public Room northExit;
public Room southExit;
public Room eastExit;
public Room westExit;
/**
* Create a room described "description".
Initially, it has
* no exits. "description" is something like "a
kitchen" or
* "an open court yard".
*/
public Room(String description)
{
this.description = description;
}
/**
* Define the exits of this room. Every direction
either leads
* to another room or is null (no exit there).
*/
public void setExits(Room north, Room east, Room
south, Room west)
{
if(north != null)
northExit = north;
if(east != null)
eastExit = east;
if(south != null)
southExit = south;
if(west != null)
westExit = west;
}
/**
* Return the description of the room (the one that
was defined
* in the constructor).
*/
public String getDescription()
{
return description;
}
}

Chapter06 designing class-zuul bad

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Chapter06 designing class-zuul bad