polymorphism

[hardik shah]

Hi,

I am a Java Student, I am running following code but it is failed, I found ferror :




=========== Code =============


// polymorphism

abstract class player // class is abstrct
{
String name;

player(String nm)
{
name=nm;
}

//public String getName() // regular method
// {
// return(name);
// }

abstract void play();
}

class cricket_player extends player
{
cricket_player(String var)
{
super(nm);
}

void play()
{
System.out.println("play cricket:");
return name;
}
}

class hockey_player extends player
{
hockey_player(String nm,String var)
{
super(nm);
}

void play()
{
System.out.println("play hockey:");
return name;
}
}

class football_player extends player
{
football_player(String nm,String var)
{
super(nm);
}

void play()
{
System.out.println("play football:");
return name;
}
}

public class mcs24IIp39
{
public static void main(String args[])
{
player ref; //set up var for an player1

cricket_player aCplayer=new cricket_player("scahin"); // makes specific objects
hockey_player aHplayer=new hockey_player("dhanaraj");
football_player aFplayer= new football_player("bhutia");

// now reference each as an animal
ref=aCplayer;
ref.play();

ref=aHplayer;
ref.play();

ref=aFplayer;
ref.play();
}
}

[JoeMac3313]

=========== Code =============

 
// polymorphism
 
abstract class player // class is abstrct
{
      String name;
 
     player(String nm)
     {
         name=nm;
     }
 
      //public String getName() // regular method
      // {
              // return(name);
      // }
 
      abstract void play();
}
 
class cricket_player extends player
{
        cricket_player(String var)
        {
                 super(nm);
        }
 
    void play()
    {
        System.out.println("play cricket:");
        return name;
    }
}
 
class hockey_player extends player
{
    hockey_player(String nm,String var)
    {
        super(nm);
    }
 
    void play()
    {
        System.out.println("play hockey:");
        return name;
    }
}
 
class football_player extends player
{
    football_player(String nm,String var)
    {
        super(nm);
    }
 
    void play()
    {
        System.out.println("play football:");
        return name;
    }
}
 
public class mcs24IIp39
{
    public static void main(String args[])
    {
        player ref; //set up var for an player1
 
        cricket_player aCplayer=new cricket_player("scahin"); // makes specific objects
        hockey_player aHplayer=new hockey_player("dhanaraj");
        football_player aFplayer= new football_player("bhutia");
 
        // now reference each as an animal
        ref=aCplayer;
        ref.play();
 
        ref=aHplayer;
        ref.play();
 
        ref=aFplayer;
        ref.play();
    }
}
 

Reminder to put code tags around code

[JosAH]

play() is a void method, i.e. it can't return anything.

kind regards,

Jos

[praveen2gupta]

Hi
There is some basic fundamental problem in the code. You wants to understand polymorphism. And you are clubbing it with abstract classes. To understand the Polymorphism there is no need of abstract clases. There classes are not linked with polmorphism. There is two Big problem in the code.

1. You should not mix abstract with polymorphism( for understanding it ).
2. Object of abstract class can't be created.(Object ref)

Polymorphism allows you to pass parameters or signatures with the same name of method with different Input parameters or signatures.

You can create more than one method with the same name but the signature should be different.

[JosAH]

Polymorphism allows you to pass parameters or signatures with the same name of method with different Input parameters or signatures.

I'd call that 'overloading'. Using an abstract class, extend it and implement the
abstract method is a form of polymorphism. Note that all the classes could
have implemented an interface instead which is another form of overloading.
The two are much alike because in both cases a type is extended, either with
implementation (extends a class) or whithout (implements an interface).

kind regards,

Jos