fib.java

import java.util.*;

class FibSequence {
  public static class FibIterator {
    private int current;
    private int limit;
    private int nextfib;
    private int lastfib;
    public FibIterator(int theLimit) {
      limit = theLimit;
      current = 0;
      lastfib = 1;
      nextfib = 2;
    }
    public void first() {}
    public int currentItem() {
      return(lastfib);
    }
    public void next() {
      int temp;
      switch(current) {
      case 0:
      case 1:
        current += 1;
      default:
        current += 1;
        temp = nextfib;
        nextfib += lastfib;
        lastfib = temp;
      }
    }
    public boolean isDone() {
      return(current == limit);
    }
  }
  public FibIterator createIterator(int theLimit) {
    return new FibIterator(theLimit);
  }
}

/* Use the iterator to cycle thru first 6 elements */

FibSequence f = new FibSequence();
FibIterator fi = f.createIterator(6);
for (fi.first(); !fi.isDone(); fi.next()) {
  System.out.print( fi.currentItem() + ":");
}