org.tbull.util
Interface IterableIterator<E>

All Superinterfaces:

Iterable<E>, Iterator<E>

All Known Implementing Classes:

Collections.LazyGrepIterator, Collections.LazyMapIterator

public interface IterableIterator<E>
extends Iterator<E>, Iterable<E>

An Iterator, which can itself be the subject of an enhanced for statement.

This comes in handy if you want to supply more than one iterator for a class. Since only one Iterator can be retrieved by the iterator() method, other methods have to be provided for the other iterators. But then, those iterators cannot be used with an enhanced for statement, because that statement relies on invocation of the iterator() method. Therefore, those iterators have to be Iterable themselves.

This interface does not introduce new methods. It just unifies Iterator and Iterable.

Normally, your custom IterableIterator would just return itself in its additional iterator() method, like this:

      class CustomList<E> implements List<E> {
          private List<E> backend = new ArrayList<E>();

          private class CustomIterator<E> implements IterableIterator<E> {
              /*
               *  implement hasNext(), next() and remove() in your custom fashion
               */

              /* make this Iterator iterable */
              public Iterator<E> iterator() {
                  return this;            // just return ourselves
              }
          }

          ...

          /* this returns the normal iterator */
          public Iterator<E> iterator() {
              return backend.iterator();  // use ArrayList's iterator
          }

          /* this returns our custom iterator */
          public IterableIterator<E> custom() {
              return new CustomIterator<E>();
          }
      }


      CustomList<Foo> foos = new CustomList<Foo>();
      ... add elements ...

      // iterate over all elements:
      for (Foo foo: foos) { ... }
      // iterate over custom elements:
      for (Foo foo: foos.custom()) { ... }
  

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Method Summary

Methods inherited from interface java.util.Iterator

hasNext, next, remove

Methods inherited from interface Iterable

iterator