Room.java

/* Alan Renaud */
/* Assignment 3 Sample Solution */
/* Using Arrays */
/* Oct. 17, 1999 */
/* Room.java */
/* An implementation of Room.java with arrays */
import java.io.*;
import java.util.*;

public class Room {

    // constants signifying the maximum number of doors
    // and rooms respectively 
    public static final int MAXDOORS = 3;
    public static final int MAXROOMS = 100;

    // Static array cave to hold all the rooms (note that we will not use
    // the element with index 0;
    public static Room[] cave = new Room[MAXROOMS+1];
    
    // instance array door which represents the doors pointed to by each
    // object
    Room[] doors;

    // Each room r has a unique id > 0.
    // nextId is the ID# of the next room to be created.
    private static int nextId = 1;
    private int id;


    // Create a new room with a unique ID# and
    // a reference to the previous room.
    public Room() {
        id = nextId;
        cave[nextId] = this;
        nextId++;
        doors = new Room[1+MAXDOORS];
    }

    // return Room with specified targetId or null of it does not exist
    public static Room findRoom(int targetId) {
        if (targetId<1 || targetId >= nextId)
            return null;
        return cave[targetId];
    }


    // farRoom(int door) is an instance method
    // that returns the Room at the far
    // side of the tunnel entered via the given door.
    // The actual Room object, not just its ID#, is
    // returned. Return null if the door does not exist,
    // or if the door number is smaller than 1 or larger than 3.
    public Room farRoom(int door) {
        if ((door<1)||(door>MAXDOORS))
            return null;
        else
            return doors[door];
    }

    // returns the index of the next free door in Room r. 
    // returns 0 if there are no free doors
    private static int nextFreeDoor(Room r) {
        int i=1;
        while(i<=MAXDOORS && r.doors[i]!=null) i++;
        if (i>MAXDOORS) i=0;
        return i;
    }

    // Method connect
    // Adds a (bi-directional) door between the two rooms. Prints a diagnostic
    // message and makes no connection when more than MAXDOORS doors is to be
    // connected to either room.
    public static void connect(Room a, Room b) {
        int doorA=nextFreeDoor(a);
        int doorB=nextFreeDoor(b);
        if ((a!=b&&doorA!=0&&doorB!=0)){
            a.doors[doorA]=b;
            b.doors[doorB]=a;
        }
        else if (a==b&&doorA <= MAXDOORS-1) {
            a.doors[doorA]=b;
            b.doors[doorA+1]=a;
        }
        else {
            if (doorA==0) {
                System.out.println("Connecting too many doors to Room " + a.ID());
            }
            else {
                System.out.println("Connecting too many doors to Room " + b.ID());
            }
        }
    }

    // Return the room id
    public int ID() {
        return id;
    }

    // returns a description of the room, including its id number and
    // where its doors lead to.
    public String toString() {
        String myInfo = "Room " + id + ".";
        for (int i=1; i<= MAXDOORS ; i++) {
            if (doors[i]!=null)
                myInfo = myInfo + " <" + i + "> --> " + doors[i].id;
        }
        return myInfo;
    }

    // Method showRooms
    // Prints a description of all objects in the class.
    public static void showRooms() {
        System.out.println();
        for(int roomCount = 1; roomCount < nextId; roomCount++) {
            System.out.println(cave[roomCount]);
        }
        System.out.println();
    }
}