fix: changes after comments

src/main/java/mate/academy/Main.java

@@ -6,14 +6,17 @@
 import mate.academy.dao.BookDao;
 import mate.academy.lib.Injector;
 import mate.academy.model.Book;
+import mate.academy.util.ConnectionUtil;
 
 public class Main {
     private static final Injector INJECTOR = Injector.getInstance("mate.academy");
 
     public static void main(String[] args) {
+        ConnectionUtil.initializeTable();
+
         BookDao bookDao = (BookDao) INJECTOR.getInstance(BookDao.class);
-        Book book1 = new Book("Book of Jungles", new BigDecimal(100));
-        bookDao.create(book1);
+        Book book = new Book("Book of Jungles", new BigDecimal(100));
+        bookDao.create(book);
 
         Optional<Book> bookById = bookDao.findById(1L);
         System.out.println(bookById);

src/main/java/mate/academy/dao/BookDaoImpl.java

@@ -9,26 +9,26 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
-import mate.academy.ConnectionUtil;
 import mate.academy.exceptions.DataProcessingException;
 import mate.academy.lib.Dao;
 import mate.academy.model.Book;
+import mate.academy.util.ConnectionUtil;
 
 @Dao
 public class BookDaoImpl implements BookDao {
     @Override
     public Book create(Book book) {
-        String sql = "INSERT INTO books (title, price) values (?, ?)";
+        String query = "INSERT INTO books (title, price) values (?, ?)";
         try (Connection connection = ConnectionUtil.getConnection();
                 PreparedStatement statement = connection.prepareStatement(
-                        sql, Statement.RETURN_GENERATED_KEYS
+                        query, Statement.RETURN_GENERATED_KEYS
                 );
         ) {
             statement.setString(1, book.getTitle());
             statement.setBigDecimal(2, book.getPrice());
             int affectedRows = statement.executeUpdate();
             if (affectedRows < 1) {
-                throw new RuntimeException(
+                throw new DataProcessingException(
                         "Expected to insert at least one row, but inserted 0 rows."
                 );
             }
@@ -45,9 +45,9 @@ public Book create(Book book) {
 
     @Override
     public Optional<Book> findById(Long id) {
-        String sql = "SELECT * FROM books WHERE id = ?";
+        String query = "SELECT * FROM books WHERE id = ?";
         try (Connection connection = ConnectionUtil.getConnection();
-                PreparedStatement statement = connection.prepareStatement(sql);
+                PreparedStatement statement = connection.prepareStatement(query);
         ) {
             statement.setLong(1, id);
             ResultSet resultSet = statement.executeQuery();
@@ -62,9 +62,9 @@ public Optional<Book> findById(Long id) {
 
     @Override
     public List<Book> findAll() {
-        String sql = "SELECT * FROM books";
+        String query = "SELECT * FROM books";
         try (Connection connection = ConnectionUtil.getConnection();
-                PreparedStatement statement = connection.prepareStatement(sql);
+                PreparedStatement statement = connection.prepareStatement(query);
         ) {
             ResultSet resultSet = statement.executeQuery();
             List<Book> books = new ArrayList<>();
@@ -79,9 +79,9 @@ public List<Book> findAll() {
 
     @Override
     public Book update(Book book) {
-        String sql = "UPDATE books SET title = ?, price = ? WHERE id = ?";
+        String query = "UPDATE books SET title = ?, price = ? WHERE id = ?";
         try (Connection connection = ConnectionUtil.getConnection();
-                PreparedStatement statement = connection.prepareStatement(sql);
+                PreparedStatement statement = connection.prepareStatement(query);
         ) {
             statement.setString(1, book.getTitle());
             statement.setBigDecimal(2, book.getPrice());
@@ -110,13 +110,12 @@ public boolean deleteById(Long id) {
             );
         }
 
-        String sql = "DELETE FROM books WHERE id = ?";
+        String query = "DELETE FROM books WHERE id = ?";
         try (Connection connection = ConnectionUtil.getConnection();
-                PreparedStatement statement = connection.prepareStatement(sql);
+                PreparedStatement statement = connection.prepareStatement(query);
         ) {
             statement.setLong(1, id);
-            int affectedRows = statement.executeUpdate();
-            return affectedRows > 1;
+            return statement.executeUpdate() > 0;
         } catch (SQLException e) {
             throw new DataProcessingException(
                     "Can not delete the book with the provided ID: " + id

src/main/java/mate/academy/model/Book.java

@@ -4,8 +4,8 @@
 
 public class Book {
     private Long id;
-    private final String title;
-    private final BigDecimal price;
+    private String title;
+    private BigDecimal price;
 
     public Book(String title, BigDecimal price) {
         this.title = title;
@@ -33,4 +33,13 @@ public String getTitle() {
     public BigDecimal getPrice() {
         return price;
     }
+
+    @Override
+    public String toString() {
+        return "Book{"
+                + "id=" + id
+                + ", title='" + title + '\''
+                + ", price=" + price
+                + '}';
+    }
 }

src/main/java/mate/academy/ConnectionUtil.java → src/main/java/mate/academy/util/ConnectionUtil.java

@@ -1,4 +1,4 @@
-package mate.academy;
+package mate.academy.util;
 
 import java.io.BufferedReader;
 import java.io.FileReader;
@@ -25,7 +25,6 @@ public class ConnectionUtil {
 
         try {
             Class.forName("com.mysql.cj.jdbc.Driver");
-            initializeTable();
         } catch (ClassNotFoundException e) {
             throw new DataProcessingException("Can not load JDBC driver");
         }
@@ -35,7 +34,7 @@ public static Connection getConnection() throws SQLException {
         return DriverManager.getConnection(DB_URL, DB_PROPERTIES);
     }
 
-    private static void initializeTable() {
+    public static void initializeTable() {
         try (Connection connection = getConnection()) {
             DatabaseMetaData databaseMetaData = connection.getMetaData();
             ResultSet resultSet = databaseMetaData.getTables(

src/main/resources/init_db.sql

@@ -1,5 +1,5 @@
 CREATE TABLE IF NOT EXISTS books (
-    id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
+    id BIGINT AUTO_INCREMENT PRIMARY KEY,
     title VARCHAR(255) NOT NULL,
     price DECIMAL
 );