Implementing Iterable in Java

Question

I have the following code

public class A extends Iterable<Integer> {
    ...
    public Iterator<Integer> iterator() {
        return new Iterator<Integer>() {

            A a;

            public boolean hasNext() {
                ...
            }

            public Integer next() {
                ...
            }

            public void remove(){
                ...
            } 
};

I would like to initialize the "a" field in the anonymous class with the instance of A that iterator method was called on. Is it possible?

Thank you.

That should be A implements Iterable.

SLaks
– SLaks

2010-04-25 17:36:26 +00:00
Commented Apr 25, 2010 at 17:36 — SLaks
– SLaks, Commented Apr 25, 2010 at 17:36

SLaks · Accepted Answer · 2010-04-25 17:27:45Z

10

You don't need to.

You can call methods on the outer class normally within the inner class.
When you compile it, the compiler will automatically generate a hidden field that contains a reference to the outer class.

To reference this variable yourself, you can write A.this. (A.this is the compiler-generated field and is equivalent to your a field)

answered Apr 25, 2010 at 17:27

SLaks

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Comments

Ricardo Marimon · Accepted Answer · 2010-04-25 17:29:45Z

1

Try this:

public class A extends Iterable<Integer> {

  public Iterator<Integer> iterator() {

      final A a = this;

      return new Iterator<Integer>() {
        public boolean hasNext() {
            // here you can use 'a'
        }
      }      
  }

}

answered Apr 25, 2010 at 17:29

Ricardo Marimon

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2 Comments

SLaks Over a year ago

Wrong. He wants the outer this.

Ricardo Marimon Over a year ago

The way it is stated is the outer 'this'. If you are in the method iterator() and you ask for 'this' (as I wrote) it refers to the object of which iterator() is a method. So 'a' refers to an object of type 'A'.

Eyal Schneider · Accepted Answer · 2010-04-25 17:29:47Z

1

Use :

A a = A.this

answered Apr 25, 2010 at 17:29

Eyal Schneider

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