Java Design pattern-------Observer pattern

* In simple terms, the viewer mode = Publisher + Subscriber. Here is a typical example of a headhunter. In the following diagram, there are two characters:
* Headhunters and people looking for work. The person who is looking for a job subscribes to a headhunter and tells that he wants to get a job, and when there is a new job opportunity,

* The Headhunter will notify the person who has subscribed to the message.

Headhunting Interface:

Package com.pattern.observer;/** * @author Qixuan.chen * Created: September 2, 2014 */public interface Subject {public    void Regis Terobserver (Observer Observer);    public void Removeobserver (Observer Observer);    public void Notifyallobservers ();}

Subscriber Interface:

Package com.pattern.observer;/** * @author Qixuan.chen * Created: September 2, 2014 */PUBLIC interface Observer {//Viewer update public void up Date (Subject Subject);}

Headhunting Implementation class:

Package Com.pattern.observer;import java.util.arraylist;import java.util.list;/** * @author Qixuan.chen *    Created: September 2, 2014 * headhunting classes */public class Headcounter implements Subject {private list<observer> observerlist;     Private list<string> joblist;        Public Headcounter () {observerlist = new arraylist<observer> ();    Joblist = new arraylist<string> (); }//Implement interface method//Get registered person @Override public void Registerobserver (final Observer Observer) {if (! Observer        List.contains (Observer)) {OBSERVERLIST.ADD (Observer); }}//delete a registered person @Override public void Removeobserver (final Observer Observer) {if (Observerlist.contain        S (Observer)) {OBSERVERLIST.REMOVE (Observer);            }}//notification @Override public void Notifyallobservers () {for (Observer observer:observerlist) {        Observer.update (this); }}//Add new work public void AddJob (final String job) {This.jobList.add (Job);    Notifyallobservers ();    }//Get work Public list<string> Getjobs () {return joblist;    } public String toString () {return joblist.tostring (); }}

Subscriber Implementation classes:

Package com.pattern.observer;/** * @author Qixuan.chen * Created: September 2, 2014 * Subscriber classes */public class Jobseeker implements Observe R{private string name;//Subscriber name public    jobseeker (string name) {        this.name = name;    }    Method of implementing the interface public    void Update (Subject Subject) {        System.out.println ("----to-------" +this.name + "------notifications");        System.out.println (subject);    }}

Test class:

Package com.pattern.observer;/** * @author Qixuan.chen * Created: September 2, 2014 * In simple terms, the viewer mode = Publisher + Subscriber. Here is a typical example of a headhunter. In the following chart there are two characters: * Headhunters and people looking for work. The person who is looking for a job subscribes to a headhunter, tells him that he wants a job, and when there is a new job opportunity, the Headhunter will notify the person who has subscribed to him. *  two interfaces, two implementations, one Test */public class Testdemo {public static void main (string[] args) {System.out.println ("----------Program Entry- -----------");     Headcounter headcounter = new Headcounter ();     Registered subscriber     Headcounter.registerobserver (new Jobseeker ("Mike"));     Headcounter.registerobserver (New Jobseeker ("Chris"));     Headcounter.registerobserver (New Jobseeker ("Jeff"));     Notify all Subscribers of new job opportunities     Headcounter.addjob ("Google job");     Headcounter.addjob ("Yahoo Job"); }}

Java Design pattern-------Observer pattern