Showing posts with label state pattern with java. Show all posts
Showing posts with label state pattern with java. Show all posts

Sunday, January 31, 2016

State design pattern with java


State pattern, which allows objects to behave in different ways depending on internal state. State is used when you need a class to behave differently, such as performing slightly different computations, based on some arguments passed through to the class.

Problem: Vehicle different status details

1. VehicleNotificationStatus – having different status details about vehicle.
package com.siva;

public enum VehicleNotificationStatus {
 
 VEHICLE_ORDERED("Vehicle-Ordered"),
 VEHICLE_ORDER_SUBMITTED_FOR_BODY_BUILD("Vehicle-Order-Submitted-For-Body-Build"),
 VEHICLE_BODY_SHOP_COMPLETED("Vehicle-Body-shop_completed"),
 VEHICLE_DELIVERED("Vehicle-Delivered"),
 INVALID("Invalid");
 
 VehicleNotificationStatus(String _type){
  this.type=_type;
 }
 private String type;
 

 public String getType() {
  return type;
 }
 public void setType(String type) {
  this.type = type;
 }

}

2. VehicleStatus interface to evaluate the different statues.
package com.siva;

  public interface VehicleStatus {
 
 public VehicleNotificationStatus evaluateVehicleStatus(String status);

  }

3. Different statues classes to implement the VehicleStatus interface.

VehicleOrdered is one type of status class is to implement VehicleStatus
package com.siva.status;

import com.siva.VehicleNotificationStatus;
import com.siva.VehicleStatus;

public class VehicleOrdered implements VehicleStatus{

 @Override
 public VehicleNotificationStatus evaluateVehicleStatus(String status) {
  System.out.println("VehicleOrdered state start");
    if(VehicleNotificationStatus.VEHICLE_ORDERED.getType().equalsIgnoreCase(status)){
    return VehicleNotificationStatus.VEHICLE_ORDERED;
  }
  return VehicleNotificationStatus.INVALID;
    
 }
 

}
2. VehicleForBodyBuild is one type of status class is to implement VehicleStatus
package com.siva.status;

import com.siva.VehicleNotificationStatus;
import com.siva.VehicleStatus;

public class VehicleForBodyBuild implements VehicleStatus{

 @Override
 public VehicleNotificationStatus evaluateVehicleStatus(String status) {
  System.out.println("VehicleForBodyBuild state start");
    if(VehicleNotificationStatus.VEHICLE_ORDER_SUBMITTED_FOR_BODY_BUILD.getType().equalsIgnoreCase(status)){
    return VehicleNotificationStatus.VEHICLE_ORDER_SUBMITTED_FOR_BODY_BUILD;
  }
  return VehicleNotificationStatus.INVALID;
    
 }

}
3. VehicleDelivered is one type of status class is to implement VehicleStatus
package com.siva.status;

import com.siva.VehicleNotificationStatus;
import com.siva.VehicleStatus;

public class VehicleDelivered  implements VehicleStatus{

 @Override
 public VehicleNotificationStatus evaluateVehicleStatus(String status) {
  System.out.println("VehicleDelivered state start");
    if(VehicleNotificationStatus.VEHICLE_DELIVERED.getType().equalsIgnoreCase(status)){
     System.out.println();
    return VehicleNotificationStatus.VEHICLE_DELIVERED;
  }
  return VehicleNotificationStatus.INVALID;
    
 }
}

4. Now we need to write Factory class which can be implement all this status details.
package com.siva;

import com.siva.status.VehicleDelivered;
import com.siva.status.VehicleForBodyBuild;
import com.siva.status.VehicleOrdered;

public class VehicleStatusFactory {
 
 public static VehicleStatus createStatus(VehicleNotificationStatus status){
  if(status.equals(VehicleNotificationStatus.VEHICLE_ORDERED)){
   return new VehicleOrdered();
  }
  else if(status.equals(VehicleNotificationStatus.VEHICLE_ORDER_SUBMITTED_FOR_BODY_BUILD)){
   return new VehicleForBodyBuild();
  }
  else if(status.equals(VehicleNotificationStatus.VEHICLE_DELIVERED)){
   return new VehicleDelivered();
  }
  else
   return null;
 }

}

5. We have completed the all the classes related to State pattern, now we need to write test class to see the results.
package com.siva;

public class TestStateDesignPattern {
 
 public static void main(String[] args) {
  
  VehicleStatus vehicleStatus =VehicleStatusFactory.createStatus(VehicleNotificationStatus.VEHICLE_ORDERED);
  VehicleNotificationStatus notificationStatus = vehicleStatus.evaluateVehicleStatus(VehicleNotificationStatus.VEHICLE_ORDERED.getType());
  System.out.println(notificationStatus);
  vehicleStatus =VehicleStatusFactory.createStatus(VehicleNotificationStatus.VEHICLE_ORDER_SUBMITTED_FOR_BODY_BUILD);
  VehicleNotificationStatus notificationStatus1 = vehicleStatus.evaluateVehicleStatus(VehicleNotificationStatus.VEHICLE_ORDER_SUBMITTED_FOR_BODY_BUILD.getType());
  System.out.println(notificationStatus1);
  vehicleStatus =VehicleStatusFactory.createStatus(VehicleNotificationStatus.VEHICLE_DELIVERED);
  VehicleNotificationStatus notificationStatus2 = vehicleStatus.evaluateVehicleStatus(VehicleNotificationStatus.VEHICLE_DELIVERED.getType());
  System.out.println(notificationStatus2);
 }

}


Output:
VehicleOrdered state start
VEHICLE_ORDERED
VehicleForBodyBuild state start
VEHICLE_ORDER_SUBMITTED_FOR_BODY_BUILD
VehicleDelivered state start

VEHICLE_DELIVERED




This is how state pattern will work.
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