Expand array once it reaches limit

Question

I have a program in which I need to print out several Movie objects (represented just by a single String) in an array. I start with a text file that already has five movies inside of it, but in the console, I am to allow the user to expand the array if he/she wants. (I cannot use an arraylist in this problem). I've attempted to design a program that does this, but I get an out of bounds exception each time I try to add a new movie. I also need to check the array to see if there is a duplicate movie object inside it? How can I do that?

Question: How can I allow the user to expand the array and add more movies to the list? How can I check the array to see if there is already a certain movie title inside of it?

public class MovieDriver {

    //variable declaration
    static Movie[] movies = new Movie[5];
    static Scanner scan = new Scanner(System.in);
    static int input = 0;
    static String title = "";

    public static void main(String[] args) throws FileNotFoundException {

        //retrieves movie data
        getData();

        System.out.println("Welcome to the favorite movie program.");

    do{ 
        System.out.println("Press 1 to print the list, 2 to add another movie, 3 to end the program.");

        input = scan.nextInt();     

        switch(input) {

        case 1: 
            for(int i = 0; i < movies.length; i++)
            {
            System.out.println(movies[i].toString());
            }

            break;

        case 2:
            System.out.println("Please enter the movie you would like to add to the list:");
            title = scan.nextLine();
            movies = Arrays.copyOf(movies, movies.length+1);
            movies[movies.length] = new Movie(title);

            break;

        case 3:
            System.out.println("Program terminated.");

            break;



            }
        } while (input != 3);
    }

    // method to retrieve data
    public static void getData() throws FileNotFoundException {
        // reads in movie data
        File MovieData = new File("./src/Movies.txt");
        Scanner fileScanner = new Scanner(MovieData);
        int i = 0;

        // while there is a new line in the data, goes to the next one
        while (fileScanner.hasNextLine()) {
            String line = fileScanner.nextLine();
            Scanner lineScanner = new Scanner(line);
            String title = lineScanner.nextLine();

            // creates a movie
            movies[i] = new Movie(title);
            i++;
        }
    }
}

Answer 1

first question: IndexOutOfBound

No need to use System.arraycopy(). You use the right method with Arrays.copyOf(). The problem comes from

movies = Arrays.copyOf(movies, movies.length+1); 
movies[movies.length] = new Movie(title);  // <--- here

After you call copyOf(), the new length of the array is 6. And when you do movies[movies.length]=... you try to access the 7th element. Just do:

movies = Arrays.copyOf(movies, movies.length+1); 
movies[movies.length-1] = new Movie(title);  // it will set the last slot of the array

But you have a second problem with the Scanner. When you scan the input with nextInt(), the end-of-line is not read. It means that if you enter 2 (add a movie), the 2 is read, but not the new-line. Then the new-line is read by title = scan.nextLine() and you have an empty title... The solution is:

case 2:
   scan.nextLine();  // <-- add this to "eat" the previous new-line
   System.out.println("Please enter the movie you would like to add to the list:");
   title = scan.nextLine();
   movies = Arrays.copyOf(movies, movies.length+1);
   movies[movies.length-1] = new Movie(title);
   break;

Second question: check duplicate

Since you just have a plain/native array and no sorting between the movies, you can implement a simple for loop like:

case 2:
   scan.nextLine();  // <-- add this to "eat" the previous new-line
   System.out.println("Please enter the movie you would like to add to the list:");
   title = scan.nextLine();
   if (!checkDuplicate(title)) {
      movies = Arrays.copyOf(movies, movies.length+1);
      movies[movies.length-1] = new Movie(title);
   }
   break;

and add a function (assuming there is a Movie#getTitle():

    private static boolean checkDuplicate(String title) {
        for (Movie m : movies) {
            if (title.equals(m.getTitle())) {
                return true;
            }
        }
        return false;
    }

Answer 2

To expand the array by 1:

Movie[] temp = new Movie[movies.length + 1];
System.arraycopy(movies, 0, temp, 0, movies.length);
movies = temp;

To check if there is a duplicate movie object, implement equals in your Movie class. Then iterate through the existing movies, and check if movies[i].equals(newMovie).

Answer 3

To expand the array, you must recreate an array of desired size and copy the content of previous array to new one.

   static Movie[] movies = new Movie[5];

  // expanding
  Movie[] newMovieArray = new Movie[10];
  for(int i = 0; i < 5; i++){
       newMovieArray[i] = movies[i];
  }
  movies = newMovieArray;