Design Pattern-iterator Pattern

Design Pattern-iterator Pattern

Definition: provides a method to access each element in an aggregate object sequentially without exposing the internal representation of the object.

Structure:

<喎?http: www.bkjia.com kf ware vc " target="_blank" class="keylink"> VcD4KPHA + yr7A/bt6wuujuw.vcd4kphbyzsbjbgfzcz0 = "brush: java;"> public interface Iterator {public Object First (); public Object Next (); public boolean isDone (); public Object currentItem ();} public class ConcreteIterator implements Iterator {private ConcreteAggregate aggregate; private int current = 0; public ConcreteIterator (ConcreteAggregate aggregate) {this. aggregate = aggregate;} @ Overridepublic Object Firs T () {// TODO Auto-generated method stubreturn aggregate. get (0) ;}@ Overridepublic Object Next () {// TODO Auto-generated method stubgObject ret = null; current ++; if (current <aggregate. count () {ret = aggregate. get (current);} return ret;} @ Overridepublic boolean isDone () {// TODO Auto-generated method stubreturn current> = aggregate. count ()? True: false;} @ Overridepublic Object currentItem () {// TODO Auto-generated method stubreturn aggregate. get (current) ;}} public abstract class Aggregate {public abstract Iterator createIterator ();} public class ConcreteAggregate extends Aggregate {private List Items = new ArrayList(); @ Overridepublic Iterator createIterator () {// TODO Auto-generated method stubreturn new ConcreteIterator (this);} public int count () {return items. size ();} public Object get (int index) {return items. get (index);} public void add (Object obj) {items. add (obj );}}The client code is as follows:

Public class Client {public static void main (String [] args) {ConcreteAggregate a = new ConcreteAggregate ();. add ("123");. add ("cainiao");. add ("Ali"); Iterator I = new ConcreteIterator (a); Object item = I. first (); while (! I. isDone () {System. out. println (I. currentItem (); I. Next ();}}}

Running result:

123

Cainiao

Alibaba