how to allow list for only two types of objects ?

[hitesh patil]

how to allow list for only two types of objects ?

[ravi suthar]

welcome to java runch hitesh patil..!
by default you can add any object to list.
but if you want only specific type you can use of generics.

[Winston Gutkowski]

hitesh patil wrote:how to allow list for only two types of objects ?

Are the two types related?

Winston

[Campbell Ritchie]

Unless they are related, that is rather contrary to the philosophy of collections, viz, that your collections contain things from a particular category.

[Ivan Jozsef Balazs]

As a work-around, you could fabricate a "synthetic" type to contain two references: either one to the first type, or one to the second type, and then declare a list for this type.

This type had two constructors: one for each given type.

Not forcibly a very nice or pleasing solution but feasible.

[Campbell Ritchie]

You can even make the object contain one type only by careful selection of the constructors

public class ThisOrThat
{
   private final Foo f;
   private final Bar b;

   public ThisOrThat(Foo f)
   {
      this.f = f;
      b = null;
   }

   public ThisOrThat(Bar b)
   {
      this.b = b;
      f = null;
   }
// etc
}

[Winston Gutkowski]

Campbell Ritchie wrote:Unless they are related, that is rather contrary to the philosophy of collections, viz, that your collections contain things from a particular category.

Yeah. I was thinking more along the lines of defining an interface that both of them implement.

Winston

[Campbell Ritchie]

I thought you meant something like that, Winston, or a common superclass.