デザインパターン研究ノート（34）-オブザーバーパターンの実現

Design Pattern Study Notes Realization Observer Pattern

オブザーバーモード
誰もがオフィスで他のことをしているので、上司が突然到着し、通知する必要があります。
1.双方向カップリングコード

package operation import java.util.ArrayList class Secretary{//Front desk secretary private ArrayList<StockObserver>observers=new ArrayList<StockObserver>() private String action public void Attach(StockObserver observer) { observers.add(observer) } public void Notify() { for(int i=0i<observers.size()i++) { observers.get(i).Update() } } public String getAction() { return action } public void setAction(String action) { this.action=action } } class StockObserver{//Look at the stock colleague class private String name private Secretary sub public StockObserver(String name,Secretary sub) { this.name=name this.sub=sub } public void Update() {//Get notification from the front desk System.out.println(sub.getAction()+name+'Close stock quotes and continue working!') } } public class Main{ public static void main(String[] args){ Secretary tongzhizhe=new Secretary() StockObserver tongshi1=new StockObserver('Little King',tongzhizhe) StockObserver tongshi2=new StockObserver('Little Li',tongzhizhe) tongzhizhe.Attach(tongshi1) tongzhizhe.Attach(tongshi2) tongzhizhe.setAction('The boss is back') tongzhizhe.Notify() } }

2、デカップリングコード

package operation import java.util.ArrayList abstract class Subject{ abstract void Attach(Observer observer) abstract void Detach(Observer observer) abstract void Notify() String action public String getAction() { return action } public void setAction(String action) { this.action=action } } class Boss extends Subject{ private ArrayList<Observer>observers=new ArrayList<Observer>() void Attach(Observer observer) { observers.add(observer) } void Detach(Observer observer) { observers.remove(observer) } void Notify() { for(int i=0i<observers.size()i++) { observers.get(i).Update() } } } class Secretary extends Subject{ private ArrayList<Observer>observers=new ArrayList<Observer>() void Attach(Observer observer) { observers.add(observer) } void Detach(Observer observer) { observers.remove(observer) } void Notify() { for(int i=0i<observers.size()i++) { observers.get(i).Update() } } } abstract class Observer{ protected String name protected Subject sub public Observer(String name,Subject sub) { this.name=name this.sub=sub } public abstract void Update() } class StockObserver extends Observer{ public StockObserver(String name,Subject sub) { super(name,sub) } public void Update() { System.out.println(sub.getAction()+name+'Close stock quotes and continue working!') } } class NBAObserver extends Observer{ public NBAObserver(String name,Subject sub) { super(name,sub) } public void Update() { System.out.println(sub.getAction()+name+'Close the NBA live broadcast and continue working!') } } public class Main{ public static void main(String[] args){ Secretary tongzhizhe=new Secretary() StockObserver tongzhizhe1=new StockObserver('Little Li',tongzhizhe) NBAObserver tongzhizhe2=new NBAObserver('Xiao Zhang',tongzhizhe) tongzhizhe.Attach(tongzhizhe1) tongzhizhe.Attach(tongzhizhe2) tongzhizhe.setAction('The boss is back') tongzhizhe.Notify() } }

三、オブザーバーモード

package operation import java.util.ArrayList abstract class Subject{ private ArrayList<Observer>observers=new ArrayList<Observer>() public void attach(Observer observer) { observers.add(observer) } public void detach(Observer onserver) { observers.remove(observer) } void Notify() { for(int i=0i<observers.size()i++) { observers.get(i).update() } } } abstract class Observer{ public abstract void update() } class ConcreteSubject extends Subject{ private String subjectState public String getSubjectState() { return subjectState } public void setSubjectState(String subjectState) { this.subjectState = subjectState } } class ConcreteObserver extends Observer{ private String name private String observerState private ConcreteSubject subject public ConcreteObserver(ConcreteSubject subject,String name) { this.name=name this.subject=subject } @Override public void update() { // TODO Auto-generated method stub observerState=subject.getSubjectState() System.out.println('The Observer'+name+'The new status is'+observerState) } } public class Main{ public static void main(String[] args){ ConcreteSubject s=new ConcreteSubject() s.attach(new ConcreteObserver(s,'X')) s.attach(new ConcreteObserver(s,'Y')) s.attach(new ConcreteObserver(s,'Z')) s.setSubjectState('ABC') s.Notify() } }