Using Inheritance

The Video class has basic information in it, and could be used for documentaries and instructional videos. But more information is needed for movie videos. Let us make a class that is similar to Video, but now includes the name of the director and a rating.

class Video
{
  String  title;    // name of the item
  int     length;   // number of minutes
  boolean avail;    // is the video in the store?

  ...               // as above
}

class Movie extends Video
{
  String  director;     // name of the director
  String  rating;       // G, PG, R, or X

  // constructor
  public Movie( String ttl, int lngth, String dir, String rtng )
  {
    super( ttl, lngth );                 // use the super class's constructor
    director = dir;  rating = rtng;      // initialize what's new to Movie
  }

}  

The class Movie is a subclass of Video. An object of type Movie has the following members in it:

  

    

      

        

        
member  
 
        
title   
inherited from Video
        
length  
inherited from Video
        
avail   
inherited from Video
        
show()  
inherited from Video
        
director
defined in Movie        
        
rating  
defined in Movie        
        
      
    
      

        
      
    
  

Both classes are defined: the Video class can be used to construct objects of that type, and now the Movie class can be used to construct objects of the Movie type.