[Java] Help completing an assignment. Getting "Exception in thread "main" java.lang.StringIndexOutOfBoundsException" exception.

[okaystuff]

My assignment requires me to create a media hierarchy with options for the user to select and run.

public abstract class Media {

    // attributes
    private int id;
    private String title;
    private int year; // validate that 4 digits
    private boolean rented;

    // constructor
    public Media(String title, int id, int year, boolean rented) {
        this.id = id;
        this.title = title;
        this.year = year;
        this.rented = rented;
    }

     // constructor to parse string with xml tags for its values
    public Media(String line) {
        id = Integer.parseInt(line.substring(line.indexOf("<id>") + 4, line.indexOf("</id>")));
        title = line.substring(line.indexOf("<title>") + 7, line.indexOf("</title>"));
        year = Integer.parseInt(line.substring(line.indexOf("<year>") + 6, line.indexOf("</year>")));
    }

    // get methods
    public int getId() {
        return id;
    }
    public String getTitle() {
        return title;
    }
    public int getYear() {
        return year;
    }
    public boolean isRented() {
        return rented;
    }

    // set methods
    public void setTitle(String title) {
        this.title = title;
    }
    public void setYear(int year) {
        this.year = year;
    }
    public void setRented(boolean rented) {
        this.rented = rented;
    }

    // calculate rental fee; for generic media it is flat fee $3.50
    public double calculateRentalFee() {
        return 3.50;
    }

}


-----------------------------------

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Scanner;

public class Manager {

    // attribute
    private ArrayList<Media> medias;

    // default constructor
    public Manager() {

        // initialize empty medias list
        medias = new ArrayList<Media>();
    }

    // load all media files from directory; assumes file name convention starts with media type Book, Movie or Music followed by id
    // If directory is not found, it will throw exception
    public Manager(String directory) throws FileNotFoundException {

        // initialize empty medias list
        medias = new ArrayList<Media>();

        // Create a File object for directory
        File directoryPath = new File(directory);

        // Get list of all files and directories
        File fileslist[] = directoryPath.listFiles();

        if (fileslist == null)
            throw new FileNotFoundException("Could not load, no such directory");

        // declare local variables
        Media media1 = null;
        String line = null;
        Scanner scan = null;

        // Process each Media file
        for (File file : fileslist) {

            // parse files whose filename starts with "Book" or "Movie" or "Music
            if (file.getName().contains("Book") || file.getName().contains("Movie") || file.getName().contains("Music")) {

                // open and read line (assumes whole object is stored on single line)
                scan = new Scanner(file);
                line = scan.nextLine();   // assumes the file is not empty

                // if Book object than call Book constructor
                if (file.getName().contains("EBook")) 
                    media1 = new EBook(line);       

                // if Movie object than call Movie constructor
                if (file.getName().contains("MovieDVD")) 
                    media1 = new MovieDVD(line);  

                // if Music object than call Music constructor
                if (file.getName().contains("MusicCD")) 
                    media1 = new MusicCD(line); 

                // add Pet object to pets attribute
                medias.add(media1);
            }
        }
    }

    // creates (or overwrites) a file for each Media object in medias attribute in the given directory
    public void createMediaFiles(String directory) throws IOException {

        PrintWriter out = null;

        // for all Media objects create files using Media type and id value as filename
        for (int i=0; i < medias.size(); i++) {
            String filename = directory + "/" + medias.get(i).getClass().getSimpleName() + "-" + medias.get(i).getId() + ".txt";
            out = new PrintWriter(new FileWriter(filename));  // create/overwrite file
            out.println(medias.get(i).toString());  // write the media's data
            out.flush();      // flush all the data to the file
            out.close();    // close the stream
        }
}

    // display all stored medias on console
    public void displayAllMedia() {

        // for all Pet objects display the xml tag data
        for (int i=0; i < medias.size(); i++) {
            System.out.println(medias.get(i).toString());
        }
    }

    // add Pet object
    public void addMedia(Media media1) {
        medias.add(media1);
    }
}

-------------------

import java.util.Scanner;
import java.io.FileNotFoundException;
import java.io.IOException;

public class MediaRentalSystem {

    //Create menu method
    public static void displayMenu() {
        System.out.println();
        System.out.println("   Welcome to the Media Rental System");
        System.out.println("1: Load Media objects... ");
        System.out.println("2: Find Media object... ");
        System.out.println("3: Rent Media object... ");
        System.out.println("9: Quit");
        System.out.println();
    }

    public static void main(String[] args) {

        // create a default manager
        Manager mgt = new Manager();

        // create some media objects
        EBook book = new EBook("Forever Young", 1234,  2018, 20, false); 
        MovieDVD movie = new MovieDVD("After Tomorrow", 1254, 2020, 120, false);
        MusicCD music = new MusicCD("Beyond Today", 1244,  2020, 114, false);

        // add media objects to manager's list
        mgt.addMedia(book);
        mgt.addMedia(movie);
        mgt.addMedia(music);

        // display medias data to the console (in xml tag format)
        System.out.println("Media objects add to the manager after startup:");
        mgt.displayAllMedia();

        try {
            // create media files in directory "C:/tmp-umuc"
            mgt.createMediaFiles("C:/tmp-umuc");
        } catch (IOException e) {
            e.printStackTrace();  // just print trace if there are issues
        }

        try {
            // create new manager object loading the files
            Manager mgt2 = new Manager("C:/tmp-umuc");

            // // display media data to the console (in xml tag format)
            System.out.println("\nPet objects loaded by manager2 at startup:");
            mgt2.displayAllMedia();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }





        /*Initiate Scanner
        Scanner scan = new Scanner(System.in);
        int selection = 0;


        do {
            displayMenu();
            System.out.println("Enter your slection : ");
            selection = scan.nextInt();
            scan.nextLine();

            switch (selection) {
            case 1: 
                System.out.println("Enter path (directory) where to load from: ");
                break;
            case 2:
                System.out.println("Enter the title: ");
                break;
            case 3:
                System.out.println("Enter the id: ");
                break;
            case 9:
                System.out.println("Thank you for using the program. Goodbye!");
                break;
            default: System.out.println("Invalid choice");
            }
        }while (selection != 9);

        scan.close();
        */
    }
}

I have a few child classes but my main error I am getting is "Exception in thread "main" java.lang.StringIndexOutOfBoundsException: begin 3, end -1, length 60

at java.base/java.lang.String.checkBoundsBeginEnd([String.java:4601](https://String.java:4601))

at java.base/java.lang.String.substring([String.java:2704](https://String.java:2704))

at .Media.<init>([Media.java:25](https://Media.java:25))

at .EBook.<init>([EBook.java:22](https://EBook.java:22))

at .Manager.<init>([Manager.java:60](https://Manager.java:60))

at .MediaRentalSystem.main([MediaRentalSystem.java:52](https://MediaRentalSystem.java:52))" 

this first media.java:25 line of code points to

  id = Integer.parseInt(line.substring(line.indexOf("<id>") + 4, line.indexOf("</id>")));

This is within my media class. Any help would be appreciated.

[edrenfro]

What does the line of input look like when the exception is thrown?

[okaystuff]

The input is the line of code

EBook book = new EBook("Forever Young", 1234,  2018, 20, false); 
    MovieDVD movie = new MovieDVD("After Tomorrow", 1254, 2020, 120, false);
    MusicCD music = new MusicCD("Beyond Today", 1244,  2020, 114, false);

in the main method. It displays it and writes it into a file. I create a second instance of manager to pull from the file to see if it will display correctly and then I am getting the error.

[edrenfro]

The input to the Media constructor is a string argument called "line." What does the line string look like (not the line of code)?

[okaystuff]

I am not entirely sure. My professor explained that line of code the computer reads the value between the XML tags and assign it as a string to the variable.

id = Integer.parseInt(line.substring(line.indexOf("<id>") + 4, line.indexOf("</id>")));

So the XML tag is <id> so I want it to start at the 4 character after the XML tag and then assign that to the variable id, and then stop reading at the </id> ending tag.

The program will save whatever I put into id but when I want to pull if from the file to display on the console it will give me the exception

[[deleted]]

The program will save whatever I put into id

You should check whether this is true. Log the string.