i have error on line 29 please help

Question

import java.util.ArrayList;
import java.util.List;

public class Book {
private String title;
private boolean borrowed;

public Book(String title) {
this.title = title;
this.borrowed = false;
}

public String getTitle() {
return title;
}

public boolean isAvailable() {
return !borrowed;
}

public void borrowBook() {
borrowed = true;
}

public void returnBook() {
borrowed = false;
}
}

import java.util.List;

public class Library {
private String address;
private List<Book> books;

public Library(String address) {
this.address = address;
this.books = new ArrayList<>();
}

public void printAvailableBooks() {
System.out.println("Available books at " + address + ":");
for (Book book : books) {
if (book.isAvailable()) {
System.out.println(book.getTitle());
}
}
}

public Book borrowBook(String title) {
for (Book book : books) {
if (book.getTitle().equals(title) && book.isAvailable()) {
book.borrowBook();
return book;
}
}
System.out.println("Error: Book not available.");
return null;
}

public void returnBook(Book book) {
if (books.contains(book)) {
book.returnBook();
} else {
System.out.println("Error: Book not in collection.");
}
}
}

Answer 1

The code provided seems mostly correct, but there are a few improvements and debugging points:

1. **Book Class:**
- It's generally a good practice to add `@Override` annotations when overriding methods, like `toString()`.
- Ensure that the `Book` class overrides the `toString()` method to provide a meaningful string representation of the book.
- The `borrowed` field should be set to `true` when the book is borrowed and `false` when it's returned.

2. **Library Class:**
- In the `borrowBook` method, it should also check if the book is available before attempting to borrow it.
- Ensure that the `printAvailableBooks()` method handles the case when there are no available books.

Here's the corrected and improved code:

```java
import java.util.ArrayList;
import java.util.List;

public class Book {
private String title;
private boolean borrowed;

public Book(String title) {
this.title = title;
this.borrowed = false;
}

public String getTitle() {
return ti

Answer 2

kedibone babra , Kamran Mushtaq ,

please do not paste the code into the text area.

it is better to create a link to the code in the playground, and post this link. so people have direct access to the code and do not need to copy/ paste to see what the issue is.

Answer 3

Kamran Mushtaq ,

both of your codes are not complete, but truncated.

Answer 4

https://sololearn.com/compiler-playground/cGVACxUXqgh7/?ref=app

Answer 5

The error on line 29 is because you are calling a method on a null object reference. Make sure to add the main method in a separate class or in one of your existing classes.

This code could be your guideline⤵️
https://sololearn.com/compiler-playground/c1L3NDi1SNTD/?ref=app

Answer 6

import java.util.ArrayList;
import java.util.List;

public class Book {
private String title;
private boolean borrowed;

public Book(String title) {
this.title = title;
this.borrowed = false;
}

public String getTitle() {
return title;
}

public boolean isAvailable() {
return !borrowed;
}

public void borrowBook() {
borrowed = true;
}

public void returnBook() {
borrowed = false;
}
}

public class Library {
private String address;
private List<Book> books;

public Library(String address) {
this.address = address;
this.books = new ArrayList<>();
}

public void addBook(Book book) {
books.add(book);
}

public void printAvailableBooks() {
System.out.println("Available books at " + address + ":");
for (Book book : books) {
if (book.isAvailable()) {
System.out.println(book.getTitle());
}
}
}

public

Answer 7

public class Main {
public static void main(String[] args) {
// Create a library
Library library = new Library("Main Street Library");

// Add books to the library
library.addBook(new Book("book 1"));
library.addBook(new Book("book 2"));
library.addBook(new Book("book 3"));

// Print available books
library.printAvailableBooks();
}
}
public void addBook(Book book) {
books.add(book);
}
Use this code