Question

I have two classes, and I would like for my second class to acces private data from the first class.

Normally I’d have:

public class GenericDictionary<T> implements GenericDictionary_interface<T> {

public class Iterator<T> extends GenericDictionary<T> {

But I have an interface, I don’t EXACTLY know how they work, sometimes they seem to not be necessary.

public class Iterator<T> implements Iterator_interface<T> {

How can I extend another class and have an interface ? Is the interface not needed ? should the interface of my Iterator<T> class be in the supper’s interface ? If so … how ?

P.S. please don’t lecture me on why I’m doing what I’m doing (aka making my own stuff instead of using the ones in java.util.*)

EDIT: Even though I decided to go with inner classes, the answer to my question is the order of extends and implements, thank you.

Answer 1

How can I extend another class and have an interface ?

You put the extends first, then the implements:

public class Iterator<T>
    extends GenericDictionary<T>
    implements Iterator_interface<T>
{

For example, in the JDK, java.util.ArrayList is given as

public class ArrayList<E>
extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, Serializable

(See its Javadoc.)