Common Java class libraries-Observer design patterns (Observable class Observer Interface) and observableobserver

Common Java class libraries-Observer design patterns (Observable class Observer Interface) and observableobserver

Link: http://www.2cto.com/kf/201310/253013.html

To implement the Observer mode, you must rely on the Observable class and Observer interface provided in the java. util package.

 

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import java.util.* ;  class House extends Observable{ // Indicates that the House can be observed    private float price ;// Price    public House(float price){          this.price = price ;      }      public float getPrice(){          return this.price ;      }      public void setPrice(float price){          // The observer should pay attention to each modification.        super.setChanged() ;    // Set the Change Point        super.notifyObservers(price) ;// Price changed        this.price = price ;      }      public String toString(){          return "House Price :" + this.price ;      }  };   class HousePriceObserver implements Observer{      private String name ;      public HousePriceObserver(String name){ // Set the name of each buyer        this.name = name ;      }      public void update(Observable o,Object arg){          if(arg instanceof Float){              System.out.print(this.name + "The price was changed :") ;              System.out.println(((Float)arg).floatValue()) ;          }      }  };  public class ObserDemo01{      public static void main(String args[]){          House h = new House(1000000) ;          HousePriceObserver hpo1 = new HousePriceObserver("Homebuyer") ;          HousePriceObserver hpo2 = new HousePriceObserver("Buyer B") ;          HousePriceObserver hpo3 = new HousePriceObserver("Homebuyer C") ;          h.addObserver(hpo1) ;          h.addObserver(hpo2) ;          h.addObserver(hpo3) ;          System.out.println(h) ; // Output house price        h.setPrice(666666) ;    // Modify the house price        System.out.println(h) ; // Output house price    }  };

 

Result: The house price is: 1000000.0 buyers C observed the price changed to: 666666.0 buyers B observed the price changed to: 666666.0 buyers A observed the price changed to: 666666.0 house price: 666666.0