The understanding and realization of the iterator pattern of GOF23 design pattern



Iterator mode

Scene:

Provides a way to traverse an aggregated object. Also known as  cursors cursor mode

Aggregated objects: Storing data

Iterator mode: Traversing data

Aggregate abstract class Aggregate

Iterator An iterative abstract class used to define the starting object, get the next object, determine whether to the end, the current object, and other abstract methods, unified interface

Specific aggregation classes: inheriting Aggregate

Specific iterator classes, inheriting Iterator, implementing methods such as Start, next, End, current object, and so on.

Usage scenarios:

Forward iterators

Back iterators

List/set built -in iterators

/** * Custom Abstract iterator interface */package Com.bjsxt.cn.iterator;

Public interface Myiterator {public void First ();//the cursor refers to the next element public void last ();//will have a table pointing to the final element public void next (); public boolean hasnext ();//Determine if there is a second element public boolean isFirst (); public boolean islast (); public Object CurrentObj ();//Get current object}

Package com.bjsxt.cn.iterator;

[email protected] * */public class Concretemyaggregate {private list<object> List = new Arraylist<objec  T> ();  public void AddObject (Object obj) {list.add (obj);}  public object Removeobj (object obj) {return list.remove (obj);}  Get iterator public myiterator Createiterator () {return new concreteiterator (); }//using an internal class definition iterator, you can directly use the properties of the external class private class Concreteiterator implements Myiterator {

The private int cursor;//defines where the cursor is used to record the Traverse @Override public void First () {cursor = 0; }

@Override public void Last () {cursor = List.size ()-1; }

@Override public boolean Hasnext () {if (Cursor < list.size ()) {return true;  } return false; }

@Override public boolean IsFirst () {return (cursor = = 0)? true:false; }

@Override public boolean islast () {return (cursor = = List.size ()-1)? True:false; }

@Override public Object CurrentObj () {if (Cursor < list.size ()) {return list.get (cursor);  } return null; }

@Override public void Next () {if (Cursor < list.size ()) {cursor++; }     }   }}

/** * Test class * April 11, 2015 21:15:43 */package com.bjsxt.cn.iterator;

public class Client {public static void main (string[] args) {concretemyaggregate CMA = new Concretemyaggregate ();  Cma.addobject ("AA");  Cma.addobject ("BB");  Cma.addobject (New Student ("Jay Chou", 10000));    Cma.addobject (1);    Myiterator iterator = Cma.createiterator (); while (Iterator.hasnext ()) {System.out.println (iterator.   CurrentObj ());  Iterator.next (); } }}

Class Student {private String name; private int id; public Student (String name, int id) {super ();  THIS.name = name; This.id = ID; } public Student () {}

Public String GetName () {return name;}

public void SetName (String name) {this.name = name;}

public int getId () {return ID;}

public void setId (int id) {this.id = ID;} @Override public String toString () {return name + "" + "ID" + ID;}}

/* * AABB Jay ID is 100001

*  *  */

The understanding and realization of the iterator pattern of GOF23 design pattern