Create a Java class named Book with instance variables title, author, ISBN, and yearPublished. Include javadoc style comments to describe your interface. Such a class would normally have methods, but you are not required to supply any methods.

What will be an ideal response?

```
/** Class for a book with title, author, ISBN and year published.
Class invariant: A Book always has a title and author.
*/
public class Book
{
/** Instance variables */
private String title;
private String author;
private String ISBN;
private int yearPublished;
}

```