How do I create nested TreeMaps?

This is somewhat related to my previous question but I've realised that I needed to deal with the issue of nesting earlier in the problem, so here's where I am. (I'm also not far off being a beginner in Java, so please bear with me).

I'm creating a simple booking system for 5 rooms which will take in names, times, room numbers and days. This has to be done using nested TreeMaps. Here's the layout of the data as I see it, where paretheses represent the boundaries of a TreeMap:

(Day, (Room #, (Time, Name)))

As far as I can see, I need one TreeMap for times and names, one for each room, then one for each day. That means one time/name treemap per room per day, which means 1 x 5 x 7 = 35 TreeMaps. Like this:

{Mon,  [Room 1,  (0600, NameA
                  0630, NameB
                  0700, NameC)
        Room 2,  (0600, NameD
                  0630, NameE)
        Room 3,  (0600, NameF
                  0630, NameG)]
Tues,  [Room 1,  (0600, Name1
                  0630, Name2)
        Room 2,  (0600, Name3
                  0630, Name4
                  0700, Name5)]}

(the different bracket types represent the boundaries of the nested TreeMaps)

Having come to that conclusion, my next problem is iterating through a loop to create all those TreeMaps. I can't seem to dynamically generate the TreeMaps using a for loop, because I can't stick a counter's variable number onto the newly-created TreeMap's name.

I did have this:

TreeMap keyDay = new TreeMap();
TreeMap keyRoom = new TreeMap();
TreeMap keyTime = new TreeMap();

but it is only three, which i开发者_C百科s clearly not enough to allow for duplication of keys - any new entries for e.g. '0900' (time key) or e.g. 'Room 1' (room key) will overwrite the old ones.

Does anyone have any suggestions? Would be much appreciated :)

I agree it is really super mega bad. But if you want to implement this functionality, I recommend HashMaps instead. Here is a class that implements the functionality you want:

public class Reservations {

static final int  DAY_SUN = 0, DAY_MON = 1, DAY_TUE = 2, DAY_WED = 3, DAY_THU = 4, DAY_FRI = 5, DAY_SAT = 6;
static final int ROOM_1 = 0, ROOM_2 = 1, ROOM_3 = 2, ROOM_4 = 3, ROOM_5 = 4;
private static HashMap<Integer[], String[]> hMap = new HashMap<Integer[], String[]>();


static String [] getStringForValue(Integer[] i){
    return hMap.get(i);
}

static TreeSet<String> getOrderedOutputStrings(){
    TreeSet<String> set = new TreeSet<String>();
    for(Entry<Integer[],String[]> e : hMap.entrySet()){
        int day_int = Reservations.getDay(e.getKey());
        int room_int = Reservations.getRoom(e.getKey());
        int time = Reservations.getTime(e.getValue());
        String name = Reservations.getGuestName(e.getValue());
        String day = Reservations.dayToString(day_int);
        String room = Reservations.roomToString(room_int);
        if(time > 0)
        set.add("DAY: " + "(" + day_int + ")" + day + " (" + room_int + ")"+ "ROOM: " + room + " :: " + name + " @ " + time);
    }
    return set;
}



static void setupMap() {
    for (int day = 0; day < 7; day++) {
        for (int room = 0; room < 5; room++) {
            addGuest(day, room, (int)(Math.random()*1000), "Bob TestCase");
        }
    }
}

static void addGuest(int day, int room, int time, String name) {
    Integer[] ref = new Integer[2];
    ref[0] = day;
    ref[1] = room;
    String[] s = new String[2];
    s[0] = Integer.toString(time);
    s[1] = name;
    hMap.put(ref, s);
}

static String[] lookupRoom(int day, int room) {
    Integer[] i = new Integer[2];
    i[0] = day;
    i[1] = room;
    return hMap.get(i);
}

static int getDay(Integer[] i){
    return i[0];
}

static int getRoom(Integer[] i ){
    return i[1];
}

static int getTime(String[] s) {
    return Integer.parseInt(s[0]);
}

public static String getGuestName(String[] s) {
    return s[1];
}

public static String dayToString(int i){
    switch(i){
        case 0:
            return "SUNDAY";
        case 1:
            return "MONDAY";
        case 2:
            return "TUESDAY";
        case 3:
            return "WEDNESDAY";
        case 4:
            return "THURSDAY";
        case 5:
            return "FRIDAY";
        case 6:
            return "SATURDAY";
        default:
            return null;
    }
}

public static String roomToString(int i){
    switch(i){
        case 0:
            return "ROOM ONE";
        case 1:
            return "ROOM TWO";
        case 2:
            return "ROOM THREE";
        case 3:
            return "ROOM FOUR";
        case 4:
            return "ROOM FIVE";
        default:
            return null;
    }
}

}

Here is a main that runs the Reservations class:

public class Main {

/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
    Reservations.setupMap(); //Run to test TODO: remove setupMap() from Reservation class 
    Reservations.addGuest(Reservations.DAY_MON, Reservations.ROOM_2, 1230, "John Doe");

    TreeSet<String> set = new TreeSet<String>();
    for(String s: Reservations.getOrderedOutputStrings()){
        System.out.println(s + "\n");
    }


}
}

And finally, using SetupMap and the single entry, it produces:

DAY: (0)SUNDAY (0)ROOM: ROOM ONE :: Bob TestCase @ 423

DAY: (0)SUNDAY (1)ROOM: ROOM TWO :: Bob TestCase @ 637

DAY: (0)SUNDAY (2)ROOM: ROOM THREE :: Bob TestCase @ 731

DAY: (0)SUNDAY (3)ROOM: ROOM FOUR :: Bob TestCase @ 424

DAY: (0)SUNDAY (4)ROOM: ROOM FIVE :: Bob TestCase @ 427

DAY: (1)MONDAY (0)ROOM: ROOM ONE :: Bob TestCase @ 335

DAY: (1)MONDAY (1)ROOM: ROOM TWO :: Bob TestCase @ 580

DAY: (1)MONDAY (1)ROOM: ROOM TWO :: John Doe @ 1230

DAY: (1)MONDAY (2)ROOM: ROOM THREE :: Bob TestCase @ 700

DAY: (1)MONDAY (3)ROOM: ROOM FOUR :: Bob TestCase @ 556

DAY: (1)MONDAY (4)ROOM: ROOM FIVE :: Bob TestCase @ 92

DAY: (2)TUESDAY (0)ROOM: ROOM ONE :: Bob TestCase @ 84

DAY: (2)TUESDAY (1)ROOM: ROOM TWO :: Bob TestCase @ 964

DAY: (2)TUESDAY (2)ROOM: ROOM THREE :: Bob TestCase @ 981

DAY: (2)TUESDAY (3)ROOM: ROOM FOUR :: Bob TestCase @ 294

DAY: (2)TUESDAY (4)ROOM: ROOM FIVE :: Bob TestCase @ 22

DAY: (3)WEDNESDAY (0)ROOM: ROOM ONE :: Bob TestCase @ 216

DAY: (3)WEDNESDAY (1)ROOM: ROOM TWO :: Bob TestCase @ 838

DAY: (3)WEDNESDAY (2)ROOM: ROOM THREE :: Bob TestCase @ 198

DAY: (3)WEDNESDAY (3)ROOM: ROOM FOUR :: Bob TestCase @ 494

DAY: (3)WEDNESDAY (4)ROOM: ROOM FIVE :: Bob TestCase @ 796

DAY: (4)THURSDAY (0)ROOM: ROOM ONE :: Bob TestCase @ 617

DAY: (4)THURSDAY (1)ROOM: ROOM TWO :: Bob TestCase @ 866

DAY: (4)THURSDAY (2)ROOM: ROOM THREE :: Bob TestCase @ 799

DAY: (4)THURSDAY (3)ROOM: ROOM FOUR :: Bob TestCase @ 242

DAY: (4)THURSDAY (4)ROOM: ROOM FIVE :: Bob TestCase @ 178

DAY: (5)FRIDAY (0)ROOM: ROOM ONE :: Bob TestCase @ 491

DAY: (5)FRIDAY (1)ROOM: ROOM TWO :: Bob TestCase @ 16

DAY: (5)FRIDAY (2)ROOM: ROOM THREE :: Bob TestCase @ 838

DAY: (5)FRIDAY (3)ROOM: ROOM FOUR :: Bob TestCase @ 63

DAY: (5)FRIDAY (4)ROOM: ROOM FIVE :: Bob TestCase @ 860

DAY: (6)SATURDAY (0)ROOM: ROOM ONE :: Bob TestCase @ 73

DAY: (6)SATURDAY (1)ROOM: ROOM TWO :: Bob TestCase @ 759

DAY: (6)SATURDAY (2)ROOM: ROOM THREE :: Bob TestCase @ 15

DAY: (6)SATURDAY (3)ROOM: ROOM FOUR :: Bob TestCase @ 115

DAY: (6)SATURDAY (4)ROOM: ROOM FIVE :: Bob TestCase @ 21

That result was generated in less than a single second. I promise that is infinitely more efficient than nested TreeMaps. Good Luck!

One would assume that the day is actually an enum, so the top level map should be an EnumMap

Map<Day, Map<String, Map<Integer, String>>> bookings = new EnumMap<Day, Map<String, Map<Integer, String>>>(Day.class);

Not really an answer, but rather a thought ;)

Indeed, as xappymah pointed out in comments, more natural approach would be to invent domain-specific types for your task. Like:

interface Room {
    String getName();
    public void bookRoom(Booking booking) throws AlreadyBookedException;
}

interface Person {
    String getName();
}

class Interval {
    Date startTime;
    long duration;
}

interface Booking {
    Interval getInterval();
    Room getBookedRoom() throws NotBookedYetException;
    Set<Person> getParticipants();
}

interface BookingUtils {
    Set<Booking> getBookingsForInterval(Interval interval);
    Set<Booking> getBookingsOfRoom(Room room);
}