/**
 * the fibonacci series implemented as an Iterable.
 */
public final class Fibonacci implements Iterable<Integer> {
  /** the next and previous members of the series. */
  private int a = 1, b = 1;

  public Iterator<Integer> iterator() {
    return new Iterator<Integer>() {
      /** the series is infinite. */
      public boolean hasNext() { return true; }
      public Integer next() {
        int tmp = a;
        a += b;
        b = tmp;
        return a;
      }
      public void remove() { throw new UnsupportedOperationException(); }
    };
  }