Java Homework Help - Tested Code, Every Line Explained

// Library Catalog System
// Purpose: Manage books with add, search, sort, and file persistence
// Course Level: OOP + File I/O (Year 2)

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Scanner;
import java.io.*;

public class LibraryCatalog {
    private ArrayList<Book> catalog;

    public LibraryCatalog() {
        this.catalog = new ArrayList<>();
    }

    /**
     * Adds a book after validating title and author are not blank.
     * Returns true if added, false if validation fails.
     */
    public boolean addBook(String title, String author, int year) {
        if (title == null || title.trim().isEmpty()) {
            System.out.println("Error: Book title cannot be blank.");
            return false;
        }
        if (author == null || author.trim().isEmpty()) {
            System.out.println("Error: Author name cannot be blank.");
            return false;
        }
        if (year < 1450 || year > 2026) {
            System.out.println("Error: Publication year out of range.");
            return false;
        }
        catalog.add(new Book(title.trim(), author.trim(), year));
        return true;
    }

    /**
     * Searches catalog by partial title match (case-insensitive).
     * Returns matching books as a new list without modifying original.
     */
    public ArrayList<Book> searchByTitle(String keyword) {
        ArrayList<Book> results = new ArrayList<>();
        if (keyword == null || keyword.trim().isEmpty()) return results;

        String lowerKeyword = keyword.toLowerCase();
        for (Book book : catalog) {
            if (book.getTitle().toLowerCase().contains(lowerKeyword)) {
                results.add(book);
            }
        }
        return results;
    }

    // ... 4 more methods: searchByAuthor, displaySorted, saveToCSV, loadFromCSV
    // Total: 185 lines across 2 classes (LibraryCatalog + Book)
}