编写一个BookDemo类，实例化一个Book对象并显示，用java运行结果

以下是BookDemo类的示例代码：

public class BookDemo {
    public static void main(String[] args) {
        // 实例化一个Book对象
        Book book = new Book("Java Programming", "John Smith", 2021, 39.99);

        // 输出Book对象信息
        System.out.println("Book Information:");
        System.out.println("Title: " + book.getTitle());
        System.out.println("Author: " + book.getAuthor());
        System.out.println("Year: " + book.getYear());
        System.out.println("Price: $" + book.getPrice());
    }
}

在运行该代码之前，需要确保Book类已经被定义。Book类的代码如下：

public class Book {
    private String title;
    private String author;
    private int year;
    private double price;

    public Book(String title, String author, int year, double price) {
        this.title = title;
        this.author = author;
        this.year = year;
        this.price = price;
    }

    public String getTitle() {
        return title;
    }

    public String getAuthor() {
        return author;
    }

    public int getYear() {
        return year;
    }

    public double getPrice() {
        return price;
    }
}

在运行BookDemo类后，控制台会输出以下结果：

Book Information:
Title: Java Programming
Author: John Smith
Year: 2021
Price: $39.99