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Design Patterns in Java (Creational) - Memento Pattern

Memento Pattern

  • Used to provide undo actions
  • Externalize internal state


Main



public static void main(String[] args) {






  



  Caretaker c = new Caretaker();



  



  Employee e = new Employee();



  e.setName("Chalan");



  e.setNumber("11111111");



  e.setAddress("NA");



  



  c.save(e);



  



  System.out.println(e);



  



  e.setNumber("2w222222");



  



  c.save(e);



  



  e.setNumber("33333");



  



  System.out.println(e);



  



  c.revert(e);



  



  System.out.println(e);



  



  c.revert(e);



  



  System.out.println(e);



 }

Caretaker



public class Caretaker {









 private Stack<EmployeeMemento> history = new Stack<EmployeeMemento>();



 



 public void save(Employee e){



  history.push(e.save());



 }



 



 public void revert(Employee e){



  e.revert(history.pop());



 }



}

Employee



public class Employee {






 



 private String name;



 private String number;



 private transient String address;



 //getters & setters

}

EmployeeMemento



public class EmployeeMemento {










 private String name;



 private String number;



 



 public EmployeeMemento( String name, String number){



  this.name = name;



  this.number = number;



 }



 



 public String getName() {



  return name;



 }



 public String getNumber() {



  return number;



 }



 



}


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