package yourpackagename;
public class Book {
String isbn;
String title;
int width;
int height;
int numberOfPages;
}
The Book class is a member of the yourpackagename package and has five fields.
Since Book is public, it can be instantiated from any other classes.
A public class must be saved in a file that has the same name as the class, and the extension must be java.
A Java source file can only contain one public class.
A Java source file can contain other classes that are not public.