ArrayList implements List Interface

[SelvarajC Chennappan]

Hi All,

AbstractList implements List and ArrayList extends AbstractList implements List.

doubt :Why ArrayList is implementing List again?

Regards,
Selvaraj C

[Jesper de Jong]

Because ArrayList extends AbstractList (which implements List), ArrayList also automatically implements List.

If you look at the source code of ArrayList (in the file src.zip inside your JDK installation directory) you'll see that it explicitly implements interface List. It's not necessary to specify this, because it already implements List via its base class. Probably the people who wrote the ArrayList class just included this for clarity.

[SelvarajC Chennappan]

Jesper Young wrote:Because ArrayList extends AbstractList (which implements List), ArrayList also automatically implements List.

If you look at the source code of ArrayList (in the file src.zip inside your JDK installation directory) you'll see that it explicitly implements interface List. It's not necessary to specify this, because it already implements List via its base class. Probably the people who wrote the ArrayList class just included this for clarity.

Thank you Jesper Young


Could you please explain the clarity, we are getting here?

[Rob Spoor]

They are just saying again that ArrayList implements List so you won't need to go to AbstractList in the Javadoc pages to find out it implements List. You can see it from the ArrayList Javadoc page immediately.