arrays

[dhana rangu]

 
class animal
{
}
class pet extends animal
{
}
class dog extends pet
{
  void method1()
  {  System.out.println("In dog"); }
}
class test
{
  public static void main(String args[])
  { 
    aniaml[] a={new animal(),new pet(),new dog()};
    a[2].method1();
  }
}
 

In the above code i am getting an error " cannot resolve the symbol method1() " when i am trying to acees method1 in the line a[2].method1().plzzz help

[Gian Franco]

Hi dhana,
When you create the array of the animal class in the
first line of the main, all the elements are upcasted
to the animal class.
In order to use your method (method1) you should
explicitly downcast a[2] (i.e. the formerly upcasted
dog object) by doing:
((dog)a[2]).method1();
Gian Franco

[dennis zined]

You didnt define method1 in either animal or pet so what would you expect?

[dhana rangu]

hi Gian franco

I got it now.Thanx for ur help

dhana

[Gian Franco]

Hi dhana,
Coming back to your question. If polymorphism is desired the base class animal should provide the common interface to the derived classes. The subclasses should override these definitions to provide unique behavior for each specific type of animals. Not defining the methods in the base class or giving them a private access specifier inhibits polymorphism.
Gian Franco