如何从不同类的 ArrayList 中删除对象？

Question

我这里有两节课要布置作业。我试图从图书馆目录中删除 Item 对象并将其添加到当前读者的 checkOutItems 中。当我运行代码时，它说我没有从目录中删除该对象。这里有什么我失踪的吗？我主要关心 CheckIn 和 CheckOut 方法。

下面的 Library.java

import java.io.File;
import java.io.FileNotFoundException;
import java.time.LocalDate;
import java.util.ArrayList;
import java.util.Scanner;

public class Library {

    private boolean isOpen;
    private Patron currPatron;
    public ArrayList<Patron> patrons;
    public ArrayList<Item> catalog;
    private LocalDate currDate;
    public ArrayList<Item> lastSearchResults = new ArrayList<>();

    public Library(ArrayList<Item> catalog, Scanner input, int year, int month, int day) {
        this.currDate = LocalDate.of(year, month, day);
        this.catalog = catalog;
        this.patrons = new ArrayList<Patron>();
    }
public ArrayList<Item> getCatalog() {
    return catalog;
}

public LocalDate getCurrDate() {
    return currDate;
}

public void start() {
    Scanner s = new Scanner(System.in);
    System.out.println("Enter o to open the library or x to exit the program.");
    String input = s.next();
    if (input.contains("x")) {
        return;
    }
    if (!input.contains("o")) {
        System.out.println("Invalid input");
    }

    System.out.println("Today's date: " + currDate + "\n");
    System.out.println("Overdue items: \n");

    System.out.println("Choose an existing patron by number, enter n to add a new patron, or enter c to close.");

    input = s.next();
    s.nextLine();

    switch (input) {
        case "c":
            break;
        case "n":
            System.out.println("Enter patron name.");
            String name = s.nextLine();
            System.out.println("Enter patron card number.");
            int cn = s.nextInt();

            Patron p = new Patron(name, cn);
            break;
    }
}

public void open() {
    this.isOpen = true;
}

public void close() {
    this.isOpen = false;
    this.currDate = currDate.plusDays(1);
}

public boolean isOpen() {
    return isOpen;
}

public ArrayList<Patron> getPatrons() {
    return patrons;
}

public void addPatron(String n, int cn) {
    Patron p = new Patron(n, cn);
    currPatron = p;
    patrons.add(p);
}

public void setPatron(int p) {
    for (Patron patron : patrons) {
        if (patron.getCardNumber() == p) {
            this.currPatron = patron;
        }
    }
}

public Patron getCurrPatron() {
    return currPatron;
}

public void search(String search) {
    lastSearchResults.clear();
    for (Item currItem : catalog) {
        if (currItem.detailedInfo().contains(search)) {
            lastSearchResults.add(currItem);
        }
    }
}

public ArrayList<Item> getSearchResults() {
    return lastSearchResults;
}

public void checkIn(int index) {
    ArrayList<Item> ls = currPatron.getItems();
    Item a = ls.get(index);
    currPatron.checkInItem(a);
    catalog.add(index, a);

}

public void checkOut(int index) {
    Item i = catalog.get(index);
    catalog.remove(index);
    currPatron.checkOutItem(i);
}

/////////////////// DO NOT CHANGE THE CODE BELOW /////////////////////

public static ArrayList<Item> readCatalog(String fileName) {

    Scanner input = null;
    try {
        input = new Scanner(new File(fileName));
    } catch (FileNotFoundException e) {
        System.out.println("File was not found.");
        System.exit(-1);
    }

    String line = "";
    ArrayList<Item> catalog = new ArrayList<Item>();
    boolean stop = false;
    while (!stop) {
        line = input.nextLine();
        switch (line) {
            case "BOOK":
                String title = input.nextLine();
                String author = input.nextLine();
                int pages = input.nextInt();
                int year = input.nextInt();
                catalog.add(new Book(title, author, pages, year));
                input.nextLine();
                break;
            case "MUSIC":
                title = input.nextLine();
                String artist = input.nextLine();
                String format = input.nextLine();
                year = input.nextInt();
                input.nextLine();
                ArrayList<String> tracks = new ArrayList<String>();
                while (true) {
                    line = input.nextLine();
                    if (line.equals("")) {
                        break;
                    }
                    tracks.add(line);
                }
                catalog.add(new Music(title, artist, format, year, tracks));
                break;
            case "VIDEO":
                title = input.nextLine();
                format = input.nextLine();
                year = input.nextInt();
                int runtime = input.nextInt();
                catalog.add(new Video(title, format, year, runtime));
                input.nextLine();
                break;
            case "END":
                stop = true;
                break;
        }
    }
    return catalog;
}

public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.println("Enter catalog file name.");
    String fileName = input.nextLine();
    int year;
    int month;
    int day;
    System.out.println("Enter the current year.");
    year = input.nextInt();
    System.out.println("Enter the current month.");
    month = input.nextInt();
    System.out.println("Enter the current day.");
    day = input.nextInt();
    input.nextLine();

    ArrayList<Item> catalog = Library.readCatalog(fileName);

    Library l = new Library(catalog, input, year, month, day);

    l.start();
}
}

Patron.java 文件

import java.util.ArrayList;

public class Patron implements Printable {

private String name;
private int cardNumber;
ArrayList<Item> checkedItems = new ArrayList<Item>();

public Patron(String n, int cn) {
    this.name = n;
    this.cardNumber = cn;
}

public String basicInfo() {
    return this.name + " (" + this.cardNumber + ")";
}

public String detailedInfo() {

    StringBuilder items = new StringBuilder();
    for (Item item : checkedItems) {
        items.append("    ").append(item.basicInfo()).append(" due on ").append(item.getDueDate()).append("\n");
    }

    String r = "Name: " + this.name + "\n"
            + "Card number: " + this.cardNumber + "\n"
            + items.toString();

    return r.trim();
}

public ArrayList<Item> getItems() {
    return this.checkedItems;
}

public void checkOutItem(Item i) {
    checkedItems.add(i);
}

public void checkInItem(Item i) {
    checkedItems.remove(i);
}

public int getCardNumber() {
    return this.cardNumber;
}
}

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