create an object of interface

[yma16]

It is said we cannot create an object of interface. What about the next code

List myIntList = new LinkedList();

Is List an interface?

The code is on page 2 of http://java.sun.com/j2se/1.5/pdf/generics-tutorial.pdf

Thanks.

[ra4king]

List is an interface, but you are not instantiating an object of List, you are instantiating an object of LinkedList.

[sunde887]

It is an interface. List is not the actual object. It is the type. The reference type can be of any superclass or interface the class implements. You could also do

Object o = new String("Hi");

You can also create an array of some interface type and fill it with implementing classes.

It has something to do with polymorphism, but it gets a bit more complicated then that. I would try and google and see what you can find out about this topic.

[Junky]

Yes List is an interface but the code does not create an instance of List, it creates an instance of LinkedList which is a concrete class.

[mutter]
stoopid phone call
[/mutter]

[yma16]

Thank you all. Why does it not use
LinkedList myIntList = new LinkedList();

Is LinkedList myIntList = new LinkedList();
more clear?

Thanks again.

[Junky]

It is generally accepted that you always use the interface type when declaring variables. Consider a method:

public void doStuff(LinkedList l) {

}

That restricts users to only be able to pass a LinkedList to the method.

public void doStuff(List l) {

}

This allows any List to be passed.

[yma16]

Thanks a lot.