listing 1
// A short package demonstration.  
package bookpack;  
  
class Book {  
  private String title;  
  private String author;  
  private int pubDate;  
  
  Book(String t, String a, int d) {  
    title = t;  
    author = a;  
    pubDate = d;  
  }  
  
  void show() {  
    System.out.println(title);  
    System.out.println(author);  
    System.out.println(pubDate); 
    System.out.println(); 
  }  
}  
  
class BookDemo {  
  public static void main(String args[]) {  
    Book books[] = new Book[5];  
  
    books[0] = new Book("Java: A Beginner's Guide", 
                        "Schildt", 2014);  
    books[1] = new Book("Java: The Complete Reference", 
                        "Schildt", 2014); 
    books[2] = new Book("The Art of Java", 
                        "Schildt and Holmes", 2003); 
    books[3] = new Book("Red Storm Rising", 
                         "Clancy", 1986);  
    books[4] = new Book("On the Road", 
                        "Kerouac", 1955);  
  
    for(int i=0; i < books.length; i++) books[i].show();  
  } 
}

listing 2
// Book recoded for public access. 
package bookpack; 
 
public class Book {  
  private String title;  
  private String author;  
  private int pubDate; 
 
  // Now public. 
  public Book(String t, String a, int d) {  
    title = t;  
    author = a;  
    pubDate = d;  
  } 
 
  // Now public. 
  public void show() {  
    System.out.println(title);  
    System.out.println(author);  
    System.out.println(pubDate);   
    System.out.println(); 
  }  
}

listing 3
// This class is in package bookpackext. 
package bookpackext; 
 
// Use the Book Class from bookpack. 
class UseBook {  
  public static void main(String args[]) {  
    bookpack.Book books[] = new bookpack.Book[5]; 
 
    books[0] = new bookpack.Book("Java: A Beginner's Guide", 
                       "Schildt", 2014);  
    books[1] = new bookpack.Book("Java: The Complete Reference", 
                       "Schildt", 2014); 
    books[2] = new bookpack.Book("The Art of Java", 
                       "Schildt and Holmes", 2003); 
    books[3] = new bookpack.Book("Red Storm Rising", 
                        "Clancy", 1986);  
    books[4] = new bookpack.Book("On the Road", 
                       "Kerouac", 1955);  
  
    for(int i=0; i < books.length; i++) books[i].show();  
  } 
}

listing 4
// Make the instance variables in Book protected. 
package bookpack; 
 
public class Book { 
  // these are now protected 
  protected String title;  
  protected String author;  
  protected int pubDate; 
 
  public Book(String t, String a, int d) {  
    title = t;  
    author = a;  
    pubDate = d;  
  } 
 
   public void show() {  
    System.out.println(title);  
    System.out.println(author);  
    System.out.println(pubDate);   
    System.out.println(); 
  }  
}

listing 5
// Demonstrate Protected.  
package bookpackext; 
 
class ExtBook extends bookpack.Book { 
  private String publisher; 
 
  public ExtBook(String t, String a, int d, String p) {   
    super(t, a, d);  
    publisher = p;  
  } 
 
  public void show() {   
    super.show();   
    System.out.println(publisher);   
    System.out.println();    
  } 
 
  public String getPublisher() { return publisher; }  
  public void setPublisher(String p) { publisher = p; } 
 
  /* These are OK because subclass can access  
     a protected member. */  
  public String getTitle() { return title; }  
  public void setTitle(String t) { title = t; }  
  public String getAuthor() { return author; }  
  public void setAuthor(String a) { author = a; }  
  public int getPubDate() { return pubDate; }  
  public void setPubDate(int d) { pubDate = d; }  
} 
 
class ProtectDemo {   
  public static void main(String args[]) {   
    ExtBook books[] = new ExtBook[5]; 
 
    books[0] = new ExtBook("Java: A Beginner's Guide", 
                      "Schildt", 2014, "McGraw-Hill");  
    books[1] = new ExtBook("Java: The Complete Reference", 
                      "Schildt", 2014, "McGraw-Hill"); 
    books[2] = new ExtBook("The Art of Java", 
                      "Schildt and Holmes", 2003, 
                      "McGraw-Hill"); 
    books[3] = new ExtBook("Red Storm Rising", 
                      "Clancy", 1986, "Putnam");  
    books[4] = new ExtBook("On the Road", 
                      "Kerouac", 1955, "Viking");  
 
    for(int i=0; i < books.length; i++) books[i].show();  
 
    // Find books by author 
    System.out.println("Showing all books by Schildt."); 
    for(int i=0; i < books.length; i++) 
      if(books[i].getAuthor() == "Schildt") 
        System.out.println(books[i].getTitle()); 
 
//    books[0].title = "test title"; // Error -- not accessible  
  }  
}

listing 6
// Demonstrate import. 
package bookpackext; 
import bookpack.*; 
 
// Use the Book Class from bookpack.  
class UseBook {  
  public static void main(String args[]) {  
    Book books[] = new Book[5];  
  
    books[0] = new Book("Java: A Beginner's Guide", 
                        "Schildt", 2014);  
    books[1] = new Book("Java: The Complete Reference", 
                        "Schildt", 2014); 
    books[2] = new Book("The Art of Java", 
                        "Schildt and Holmes", 2003); 
    books[3] = new Book("Red Storm Rising", 
                         "Clancy", 1986);  
    books[4] = new Book("On the Road", 
                        "Kerouac", 1955);  
  
    for(int i=0; i < books.length; i++) books[i].show();  
  } 
}