Design Patterns Java™ Workbook

Appendix B. Solutions

Iterator (Chapter 28)..................................................................................................................................

SOLUTION 28.1....................................................................................................................................

A working program is:

package com.oozinoz.applications;
import com.oozinoz.fireworks.*;
public class ShowFireworkList
{
public static void main(String[] args)
{
FireworkList flist =
Promo.getPromotionalFireworks();
FireworkList.Itr i = flist.iterator();

while (i.hasNext())
{
Firework f = i.next();
System.out.println(
f.getName()

• ", $" + f.getPrice()


• ", " + f.getType());
  }
  }
  }

SOLUTION 28.2....................................................................................................................................

As Chapter 16, Factory Method, describes, iterators provide a classic example of
the FACTORY METHOD pattern. A client that wants an iterator for an instance of
a ProcessComponent knows when to create the iterator, but the receiving class knows
which class to instantiate.

SOLUTION 28.3....................................................................................................................................

You need to change the next() code to not return the node of a composite that you're
iterating over. You also need to pass along the value of the showInterior Boolean to
subiterators you create:

public Object next()
{
if (peek != null)
{
Object o = peek;
peek = null;
return o;
}

if (!visited.contains(node))
{
visited.add(node);