Java/com/study/demo3/Library.java

package com.study.demo3;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Library {

  private Map<String, Book> books;

  public Library() {
    this.books = new HashMap<>();
  }

  public void addBook(Book b) {
    String isbn = b.getIsbn();

    if (books.containsKey(isbn)) {
      System.out.println("The book already exists, adding it failed.");
    } else {
      books.put(isbn, b);
      System.out.println("Book added successfully: " + b.getTitle());
    }
  }

  public List<Book> searchAvailableBooks() {
    List<Book> availableBooks = new ArrayList<>();

    for (Book book : books.values()) {
      if (book.isAvailable()) {
        availableBooks.add(book);
      }
    }
    return availableBooks;
  }
}