Design mode-iterative mode (iterator pattern) Java iterator (iterator) detailed explanation

The iterative pattern (iterator pattern) Java iterator (iterator) explains in detail

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Reference iterator pattern (iterator pattern): http://blog.csdn.net/caroline_wendy/article/details/35254643

The Java Standard library (util) includes an iterator interface (iterator interface), an import java.util.Iterator;

The inheritance (implements) iterator interface (Iterator) needs to override (override) Three functions: Hasnext (), Next (), and remove ();

The aggregation types of Java, such as ArrayList , include iterators.

However, the array type requires rewriting the corresponding iterator (iterator).

Detailed method:

1. The ArrayList type , including the iterator method, can be returned directly.

/** * @time June 20, 2014 */package iterator;import java.util.arraylist;import java.util.iterator;/** * @author C.L.Wang * * *  public class Pancakehousemenu implements Menu {arraylist<menuitem> menuitems;/** * */public pancakehousemenu () {// TODO auto-generated Constructor stubmenuitems = new arraylist<menuitem> (); AddItem ("K&b ' pancake Breakfast", "Pancakes with scrambled eggs, and toasts", true, 2.99); AddItem ("Regular Pancake Breakfast", "pancakes with fried eggs, sau Sage ", false, 2.99); AddItem (" Blueberry pancakes "," pancakes made with fresh blueberries ", true, 3.49); AddItem (" Waffles ", "Waffles, with your choice of blueberries or strawberries", true, 3.59);} public void AddItem (string name, String Description,boolean Vegetarian, double price) {MenuItem MenuItem = new MenuItem (NA Me, description, vegetarian, price); Menuitems.add (MenuItem);} Public iterator<menuitem> Createiterator () {return menuitems.iterator ();}}

2. array type , create the corresponding iterator class , inherit (implements) iterator (Iterator), override the Iterator method .

/** * @time June 26, 2014 */package iterator;import java.util.iterator;/** * @author C.l.wang * */public class Dinermenu Impl Ements Menu {static final int max_items = 6;int Numberofitems = 0; menuitem[] menuitems;/** * */public dinermenu () {//TODO auto-generated constructor stubmenuitems = new Menuitem[max_item S];additem ("Vegetarian BLT", "(Fakin ') Bacon with lettuce & tomato on whole Wheat", true, 2.99); AddItem ("BLT", "Bacon with lettuce & tomato in the whole wheat ", false, 2.99); AddItem (" Soup of the Day "," Soup of the Day ", with a side of PO Tato Salad ", false, 3.29); AddItem (" Hotdog "," A hot dog, with saurkraut, relish, onions, topped with cheese ", false, 3.05); }public void AddItem (string name, String Description,boolean Vegetarian, double price) {MenuItem MenuItem = new MenuItem (n Ame, description, vegetarian, price); if (Numberofitems >= max_items) {System.err.println ("Sorry, menu is full! Can ' t Add item to Menu ");} else {Menuitems[numberofitems] = Menuitem;++numberofitems;}} PUblic iterator<menuitem> Createiterator () {return new dinermenuiterator (MenuItems);}} /** * @time June 27, 2014 */package iterator;import java.util.iterator;/** * @author C.l.wang * */public class Dinermenuitera Tor implements iterator<menuitem> {menuitem[] items;int position = 0;/** * */public dinermenuiterator (menuitem[] It EMS) {//TODO auto-generated constructor stubthis.items = items;} /* (non-javadoc) * @see iterator.  Iterator#hasnext () */@Overridepublic Boolean hasnext () {//TODO auto-generated method stubif (position >= items.length || Items[position] = = null) {return false;} return true;} /* (non-javadoc) * @see iterator. Iterator#next () */@Overridepublic MenuItem Next () {//TODO auto-generated method Stubmenuitem MenuItem = items[position]; ++position;return MenuItem;} @Overridepublic void Remove () {if (position <= 0) {throw new IllegalStateException ("You can ' t remove a item until you ' ve done at least one next () ");} if (items[position-1]! = null) {for (int i=position-1; i< (items.length-1); ++i) {Items[i] = items[i+1];} ITEMS[ITEMS.LENGTH-1] = null;}}}

3. Menu Interface (interface), including methods for creating Iterators (Createiterator) .

/** * @time June 27, 2014 */package iterator;import java.util.iterator;/** * @author C.l.wang * */public interface Menu {Publ IC iterator<menuitem> createiterator ();}

4. Detailed menu items, arraylist and the basic elements of the array.

/** * @time June 20, 2014 */package iterator;/** * @author C.l.wang * */public class MenuItem {String name; String Description;boolean Vegetarian; is vegetarian double price;/** *  */public MenuItem (string name, string description, Boolean vegetarian, double price) {//TOD O auto-generated Constructor stubthis.name = name;this.description = Description;this.vegetarian = vegetarian; This.price = Price;} Public String GetName () {return name;} Public String GetDescription () {return description;} Public double GetPrice () {return price;} public Boolean Isvegetarian () {return vegetarian;}}

5. Customer Class (client), call iterator (iterator) method.

/** * @time June 27, 2014 */package iterator;import java.util.iterator;/** * @author C.l.wang * */public class Waitress {Menu Pancakehousemenu; Menu dinermenu;/** * */public Waitress (menu pancakehousemenu, menu dinermenu) {//TODO auto-generated constructor Stubthi S.pancakehousemenu = Pancakehousemenu;this.dinermenu = Dinermenu;} public void Printmenu () {iterator<menuitem> pancakeiterator = Pancakehousemenu.createiterator ();Iterator< menuitem> dineriterator = Dinermenu.createiterator (); System.out.println ("menu\n----\nbreakfast");p Rintmenu (pancakeiterator); System.out.println ("\nlunch");p Rintmenu (dineriterator);} private void Printmenu (Iterator<menuitem> Iterator) {while (Iterator.hasnext ()) {MenuItem MenuItem = (MenuItem) Iterator.next (); System.out.print (Menuitem.getname () + ":"); System.out.print (Menuitem.getprice () + "--"); System.out.println (Menuitem.getdescription ());}}}

6. Test:

/** * @time June 27, 2014 */package iterator;/** * @author C.l.wang * */public class Menutestdrive {/** * @param args */publi c static void Main (string[] args) {//TODO auto-generated method Stubpancakehousemenu Pancakehousemenu = new Pancakehousem ENU ();D inermenu dinermenu = new Dinermenu (); Waitress waitress = new Waitress (Pancakehousemenu, Dinermenu); Waitress.printmenu ();}}

7. Output:

MENU----breakfastk&b ' s pancake breakfast:2.99--pancakes with scrambled eggs, and toastregular pancake Breakfast:2. Pancakes with fried eggs, sausageblueberry pancakes:3.49 – pancakes made with fresh blueberrieswaffles:3.59--Wa Ffles, with your choice of blueberries or Strawberrieslunchvegetarian blt:2.99 – (Fakin ') Bacon with lettuce & Tomat O on whole wheatblt:2.99 – Bacon with lettuce & tomato on the whole wheatsoup of the day:3.29 – Soup of the day, W ith a side of potato saladhotdog:3.05--a hot dog, with saurkraut, relish, onions, topped with cheese

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Design mode-iterative mode (iterator pattern) Java iterator (iterator) detailed explanation