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State Pattern

06 Temmuz 2010, 23:12

Bir objenin durumunu belirtmek için kullanılır. Objenin durumu runtime de sürekli değişiyorsa kullanılması uygun olur.

 

 

Örnek Java Implementasyonu:

 

 

State interface i ve iki implemantasyonu.

 

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interface State {
  public void writeName(StateContext stateContext, String name);
}
 
class StateA implements State {
  public void writeName(StateContext stateContext, String name) {
    System.out.println(name.toLowerCase());
    stateContext.setState(new StateB());
  }
}
 
class StateB implements State {
  private int count=0;
  public void writeName(StateContext stateContext, String name){
    System.out.println(name.toUpperCase());
    // change state after StateB's writeName() gets invoked twice
    if(++count>1) {
      stateContext.setState(new StateA());
    }
  }
}

 

StateContext class i state objelerini tutar. 

 
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public class StateContext {

  private State myState; 

  public StateContext() { 

    setState(new StateA()); 

  } 

 

        // normally only called by classes implementing the State interface

  public void setState(State newState) { 

    this.myState = newState; 

  }

 

  public void writeName(String name) { 

    this.myState.writeName(this, name); 

  } 

}


 

Kullanımı

 

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public class TestClientState {
  public static void main(String[] args) {
    StateContext sc = new StateContext();
    sc.writeName("Monday");
    sc.writeName("Tuesday");
    sc.writeName("Wednesday");
    sc.writeName("Thursday");
    sc.writeName("Saturday");
    sc.writeName("Sunday");
  }
}

 

Output 

 
monday
TUESDAY
WEDNESDAY
thursday
SATURDAY
SUNDAY
Category: Design Patterns, Java  |  Yorum (RSS)  |  Geri İzleme

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