casting

[nitin sharma]

a reference to an object can be cast into a reference of type InterfaceName if the class of the object implements Interface, if the object is a subinterface of InterfaceName or if the object is an array type and InterfaceName is the Cloneable interface.
Can anybody please show a constructive example which has every thing mentioned in the above line.I tried to work out an example but not able to do it properly.Please,Please help me.

[Ajith Kallambella]

Try this. The code is self explanatory.

interface Automobile
{
public void drive();
}

// Sub-interface
interface SnowMobile extends Automobile
{
public void snowDrive();
}

class Car implements Automobile 
{
public void drive() { System.out.println( " Driving a car ...."); }
}

class AmphibianCar implements SnowMobile
{

public void drive() { System.out.println( " Driving a SnowMobile on road...."); }
public void snowDrive() {System.out.println( " Driving a SnowMobile on snow....");  }
}

// Stand alone class, has no connection with any interface.
class Aeroplane
{
public void Fly() { System.out.println( " Flying a Jumbo Jet ...."); }
}
public class CastingDemo
{

public static void main ( String s[] )
{
// Test candidates.
Aeroplane Northwest = new Aeroplane();
Car  Mercedes  = new Car();
AmphibianCarBondCar   = new AmphibianCar();


// 
// A reference to an object can be cast into a reference of type InterfaceName  -
// Rule 1 : if the class of the object implements Interface.
// Rule 2 : if the object implements a subinterface of InterfaceName 
//
// Valid castings - 
Automobile a1 = (Automobile)Mercedes ;// Direct implementation
SnowMobile s1 = (SnowMobile )BondCar ;// Direct implementation
Automobile a2 = (Automobile)BondCar  ;// Implementation of subinterface.

// Invalid castings -
// Automobile a3 = (Automobile)Northwest ;// Compiles fine, but throws ClassCastException when run.
// SnowMobile s2 = (SnowMobile)Mercedes ;// Compiles fine, but throws ClassCastException when run.

// 
// A reference to an object can be cast into a reference of type InterfaceName  -
// Rule 3 : if the object is an array type and InterfaceName is the Cloneable interface.
//
Automobile HertzFleet[]  = new Car[10];
Aeroplane  FlightsToNY[] = new Aeroplane[20];

// Valid castings -
Automobile a5[] = ( Automobile[]) HertzFleet ;
Aeroplane  f2[] = ( Aeroplane[] )  FlightsToNY ;
Cloneable c1 = ( Automobile[] ) HertzFleet ;
Cloneable c2 = ( Aeroplane[]  ) FlightsToNY ;

// Invalid castings - 
Automobile a6 = ( Automobile[]) HertzFleet ;
Cloneable  c3 = ( Automobile ) HertzFleet ;   

}
}

Cheers!
------------------
Ajith Kallambella M.
Sun Certified Programmer for the Java�2 Platform.
IBM Certified Developer - XML and Related Technologies, V1.

[nitin sharma]

somebody,please come up with something.