//Chapter 9
//part 5   constructors

public class Inheritance5 {

    public static void main( String[] args ) {
	System.out.print( "creating an X:  " );
	X x1 = new X();

	System.out.println( "" );

	System.out.print( "creating an X(4):  " );
	X x2 = new X(4);

	System.out.println( "" );

	System.out.print( "creating an Y():  " );
	Y y1 = new Y();

	System.out.println( "" );

	System.out.print( "creating an Y(3.0):  " );
	Y y2 = new Y(3.0);

	System.out.println( "" );

	System.out.print( "creating an Y(3):  " );
	Y y3 = new Y(3);

    }
}



class X {
    int superField;

    X() {
	System.out.println( "hello from X() constructor" );
    }
    //if no constructor exists, compiler creates one (the "default 
    // constructor" of no arguments) that does nothing.

    X( int sf ) {
	superField = sf;
	System.out.println( "hello from X(int) constructor" );
    }
    //if any constructor exists, the default one will not be created.
}


class Y extends X {
    Y() {
	//implicit call to superclass no-arg constructor is here: super()
	System.out.println( "hello from Y() constructor" );
    }

    Y( double d ) {
	//implicit call to superclass no-arg constructor is here.
	System.out.println( "hello from Y(double) constructor" );
    }
    //if a subclass constructor implicitly (or explicitly) calls the no
    // argument constructor of superclass and it doesn't exist: syntax error 

    Y( int i ) {
	//want to initialize inherited field, typically do so with
	//superclass's constructor.
	//don't want implicit call to superclass no-arg constructor.
	//need explicit call to superclass' X(int) constructor:
	super( i );
	//the superclass must have such a constructor, else syntax error

	System.out.println( "hello from Y(int) constructor" );
    }
}