No-argument Constructor

Examine the following proposed constructor for Movie. It uses the setter methods of the parent class to initialize variables inherited from the parent. The child has these setter methods by inheritance.

// proposed constructor
public Movie( String ttl, int lngth, String dir, String rtng )
{
  setTitle( ttl );    // initialize inherited variables 
  setLength( lngth );  
  setAvailable( true );
  
  director = dir;    // initialize Movie variables
  rating = rtng;
}

It looks like this does not invoke a parent class constructor. All variables are initialized in this constructor including those variables defined in the parent class. However, a constructor from the parent class is always invoked even if you don't explicitly ask for it. The Java compiler regards the above code as shorthand for the following:

// proposed constructor
public Movie( String ttl, int lngth, String dir, String rtng )
{
  super();          // inserted by compiler: parent's no-argument constructor
  setTitle( ttl );    // initialize inherited variables 
  setLength( lngth );  
  setAvailable( true );
 
  director = dir;  // initialize Movie variables
  rating = rtng;
}

As always, super() comes first, even if you don't write it in. If the parent does not have a no-argument constructor, then using this shorthand causes a syntax error.

In our program the class definition for Video (the superclass) lacks a no-argument constructor. The proposed constructor (above) calls for such a constructor so it would cause a syntax error.

Answer:

No-argument Constructor

QUESTION 13: