package headfirst.combining.composite;import java.util.Iterator;import java.util.ArrayList;public class Flock implements Quackable {	ArrayList quackers = new ArrayList(); 	public void add(Quackable quacker) {		quackers.add(quacker);	} 	public void quack() {		Iterator iterator = quackers.iterator();		while (iterator.hasNext()) {			Quackable quacker = (Quackable)iterator.next();			quacker.quack();		}	} 	public String toString() {		return "Flock of Quackers";	}}