Question

I’m just wondering is there a way to make the ‘null’ that is outputted when using a for loop output white space?

For example, I have a 2d array of an type object and when displaying the array I want to display the first three elements and then skip say 10 empty spaces then print another three elements.

Also if I was to use a random generator to pick array elements at random would the empty elements affect this or not?

Main:

public class CinemaSystem {

    public static void main(String[] args) {
        Seat cinemaactual = new Seat("Cinema");
        Seat[][] cinema = new Seat[12][23];

        Ticket ticket = new Ticket();
        Scanner scan = new Scanner(System.in);
        String answer, contiune;

        int number, check = 0, category, id;

        do {
            System.out.print("Welcome to the Theatre Booking System. (QUIT to exit)"
                    + "\nWould you like to purchase tickets or list available seats?"
                    + "(/Purchase/List/Help)");
            answer = scan.nextLine();

            if (answer.equalsIgnoreCase("purchase")) {
                do {

                    System.out.println("Please choose the cateogry of ticket "
                            + "you would like, followed by who the ticket is for"
                            + "and the amount required. (separated by a space)\n"
                            + "1. Gold\n2. Silver\n3. Bronze\n\n1. Adult\n2."
                            + " Child\n3. Concession");
                    category = scan.nextInt();
                    number = scan.nextInt();
                    id = scan.nextInt();
                    if (category == 1 || category == 2 || category == 3 && id == 1 || id == 2 || id == 3) {
                        ticket.SetType(category);
                        if (category == 1) {
                            ticket.SetName("Gold");
                        } else if (category == 2) {
                            ticket.SetName("Siler");
                        } else {
                            ticket.SetName("Bronze");
                        }
                        ticket.SetNumber(number);
                        ticket.SetID(id);
                        if (id == 1) {
                            ticket.SetCategory("Adult");
                        } else if (id == 2) {
                            ticket.SetCategory("Child");
                        } else {
                            ticket.SetCategory("Bronze");
                        }
                        System.out.print("You have selected"
                                + ticket.GetNumber() + " " + ticket.GetName()
                                + " ticket(s) at the" + ticket.GetCategory() + " price .");

                        ticket.BuyTicket(category, id, number);
                    } else {
                        System.out.print("Sorry, incorrect input, please enter an apropriate value.");
                        check = scan.nextInt();
                    }
                } while (check == 0 || check > 3);

                do {
                    System.out.print("Would you like to perchase more tickets? (Yes/No)");
                    contiune = scan.nextLine();
                } while (contiune.equalsIgnoreCase("Yes"));
            } else if (answer.equalsIgnoreCase("list")) {
                cinemaactual.CreateTheatre(cinema);
                cinemaactual.DisplayTheatre(cinema);
            } else if (answer.equalsIgnoreCase("help")) {
                // Code for help
            } else if (answer.equalsIgnoreCase("quit")) {
                System.exit(-1);
            }

            System.out.print("Sorry, incorrect input please enter"
                    + " a valid input (Purchase/List/Help or QUIT to exit");
            answer = scan.nextLine();

        } while (!answer.equalsIgnoreCase("purchase")
                || !answer.equalsIgnoreCase("List")
                || !answer.equalsIgnoreCase("help")
                || !answer.equalsIgnoreCase("quit"));
    }
}

Method in the class that makes the array:

public Seat[][] CreateTheatre(Seat[][] x) {
for (int row = 0; row < 8; row++) {
    for (int col = 0; col < 4; col++) {
        x[row][col] = new Seat("B");
    }
}

for (int row = 8; row < 12; row++) {
    for (int col = 0; col < 4; col++) {
        x[row][col] = new Seat("S");
    }
}

for (int row = 0; row < 8; row++) {
    for (int col = 19; col < 23; col++) {
        x[row][col] = new Seat("B");
    }
}

for (int row = 8; row <12; row++){
    for (int col = 19; col < 23; col++) {
        x[row][col] = new Seat("S");
    }
}

for (int row = 3; row < 5; row++) {
    for (int col = 4; col < 9; col++) {
        x[row][col] = new Seat("B");
    }
}

for (int row = 3; row < 5;row++){
    for (int col = 14; col < 19; col++) {
        x[row][col] = new Seat("S");
    }
}

for (int row = 9; row < 12; row++) {
    for (int col = 7; col < 4; col++) {
        x[row][col] = new Seat("S");
    }
}

for (int row = 3; row < 5; row++) {
    for (int col = 14; col < 20; col++) {
        x[row][col] = new Seat("B");
    }
}

for (int row = 5; row < 9; row++) {
        for (int col = 4; col < 9; col++){
        x[row][col] = new Seat("S");
    }
}

for (int row = 5; row < 9; row++) {
    for (int col = 14; col < 20; col++) {
        x[row][col] = new Seat("S");
    }
}

for (int row = 6; row < 9; row++) {
    for (int col = 9; col < 14; col++) {
        x[row][col] = new Seat("G");
    }
}

for (int row = 9; row < 12; row++) {
    for (int col = 7; col < 16; col++) {
        x[row][col] = new Seat("G");
    }
}
return x;
}

For the display of the array:

public void DisplayTheatre(Seat[][] x) {
    for (int row = 0; row < x.length; row++) {
        for (int col = 0; col < x[row].length; col++) {
            System.out.print(x[row][col] + "  ");
        }
        System.out.println();
    }
}

Just wondering if I can remove the null since I want some objects display then blank space in the middle and then some more, on the same line.

Also do null elements interfere with randomly selecting elements from an array, like will a null element ever be randomly selected?

Answer 1

if i understand your requirement. below is something you are looking for .

  String[] arr = new String[5];
       arr[0]="2";
       arr[1]="3";
       arr[4]="5";
       for(int i=0; i<arr.length; i++){
           if(arr[i]==null){
               System.out.println(' ');
           }
           else {
               System.out.println(arr[i]);
           }
       }