Question

This is what I have in my method to randomly select a element in my array, however I’m not sure why it isn’t working, I feel like I have tried every way of writing it, any ideas.

public static Seat BookSeat(Seat[][] x){

  Seat[][] book = new Seat[12][23];

    if (x != null){  

      book = x[(Math.random()*x.length)];  

    }

  return book;    
}

Answer 1

The way you explain things makes me think a couple of concepts somehow got crosswired. I am assuming that book is some (2 dimensional) array of Seat objects from which you want to pick a random one. In order to do so, you need to specify a random choice for each dimension of the array:

// this should be declared elsewhere because if it's local to bookSeat it will be lost
// and reinitialized upon each call to bookSeat
Seat[][] book = new Seat[12][23];

// and this is how, after previous declaration, the function will be called
Seat theBookedSeat = bookSeat(book);

// Okay, now we have selected a random seat, mark it as booked, assuming Seat has a 
// method called book:
theBookedSeat.book();


// and this is the modified function.  Note also that function in Java by convention
// start with a lowercase letter.
public static Seat bookSeat(Seat[][] x){
    if (x != null){  
        // using Random as shown by chm052
        Random r = new Random();
        // need to pick a random one in each dimension
        book = x[r.nextInt(x.length)][r.nextInt(x[0].length)];  
    }
    return book;  
}

You should also integrate a test to check whether the selected seat was already booked and repeat the selection:

        do {
            // need to pick a random one in each dimension
            book = x[r.nextInt(x.length)][r.nextInt(x[0].length)];
        while (book.isBooked()); // assuming a getter for a boolean indicating
                                 // whether the seat is booked or not

But a full-random selection like this has a couple of disadvantages:

1. the selection being random, you can repeatedly fall on already booked seats, and the chances that happens increase with the number of already booked seats. But even with few booked seats you could be really unlucky and see the loop spin around tens of times before it hits an unbooked seat.
2. you should absolutely test whether there are still unbooked seats left before entering the loop or it will spin indefinitely.

Therefore it might be a good idea to implement a smarter selection routine, eg by randomly picking a row and a seat and start searching from there until the first free seat is encountered, but for first steps this one should do just fine.

I hope this is what you wanted to achieve, if not feel free to comment and allow me to correct and adapt.