State Pattern

State Pattern: Allow an object to alter its behaviour when it’s internal state changes. The object will appear to change its class..

Example

State.java

package com.statepattern.example;

public interface State {
 
 public void insertCard();
 public void ejectCard();
 public void enterAmount();
 public void dispense();
 
}

NoCardState.java

package com.statepattern.example;

public class NoCardState implements State {
 
 CashMachine cashMachine;

 public NoCardState(CashMachine cashMachine) {
  this.cashMachine = cashMachine;
 }

 @Override
 public void insertCard() {
  System.out.println("Please insert your card now");
  cashMachine.setState(cashMachine.getHasCardState());
  
 }

 @Override
 public void ejectCard() {
  System.out.println("Can't return anything as there is no Card");
  
 }

 @Override
 public void enterAmount() {
  System.out.println("Can't enter amount now as there is no card");
 }

 @Override
 public void dispense() {
  System.out.println("Can't dispense amount now as there is no card");
 }
 
 public String toString(){
  return "No Card State";
 }

}

HasCardState.java

package com.statepattern.example;

public class HasCardState implements State{
 
 CashMachine cashMachine;

 public HasCardState(CashMachine cashMachine) {
  this.cashMachine = cashMachine;
 }

 @Override
 public void insertCard() {
  System.out.println("you can't insert another Card");
 }

 @Override
 public void ejectCard() {
  System.out.println("Your card is returned now");
  cashMachine.setState(cashMachine.getNoCardState());
  
 }

 @Override
 public void enterAmount() {
  cashMachine.setState(cashMachine.getWorkingState());
 }

 @Override
 public void dispense() {
  System.out.println("cash Machine is already dispensing");
  
 }
 
 public String toString(){
  return "Has Card State";
 }

} 

WorkingState.java

package com.statepattern.example;

public class WorkingState implements State {
 
 CashMachine cashMachine;

 public WorkingState(CashMachine cashMachine) {
  this.cashMachine = cashMachine;
 }

 @Override
 public void insertCard() {
  System.out.println("You can't insert card Now as processing is in progress");
  
 }

 @Override
 public void ejectCard() {
  System.out.println("You can't eject card Now as processing is in progress");
  
 }

 @Override
 public void enterAmount() {
  System.out.println("Already Processing your Transcation Please wait");
 }

 @Override
 public void dispense() {
  if(cashMachine.getBalance()>cashMachine.getWithdrawAmt()){
   cashMachine.setBalance(cashMachine.getBalance()-cashMachine.getWithdrawAmt());
   System.out.println("Dispensing  amount " + cashMachine.getWithdrawAmt());
   System.out.println("Now Balance is " + cashMachine.getBalance());
   cashMachine.setState(cashMachine.getNoCardState());
  }else{
   System.out.println("Sorry!.. Sufficient balance is not available");
   cashMachine.setState(cashMachine.getOutofServiceState());
  }
  
  
 }
 
 public String toString(){
  return "Working State";
 }

}

OutofServiceState.java

package com.statepattern.example;

public class OutofServiceState implements State {
 
 CashMachine cashMachine;

 public OutofServiceState(CashMachine cashMachine) {
  this.cashMachine = cashMachine;
 }

 @Override
 public void insertCard() {
  System.out.println("Can't insert card now as cash Machine is out of Service");
  
 }

 @Override
 public void ejectCard() {
  System.out.println("Can't eject Card now as cash Machine is out of Service");
  
 }

 @Override
 public void enterAmount() {
  System.out.println("Can't enter amount  now as cash Machine is out of Service");
  
 }

 @Override
 public void dispense() {
  System.out.println("Can't dispense amount now as cash Machine is out of Service");
  
 }
 public String toString(){
  return "OutofService State";
 }

}

CashMachine.java

package com.statepattern.example;

public class CashMachine {
 
 private State hasCardState;
 private State noCardState;
 private State workingState;
 private State outofServiceState;
 //setting the default state to Out of Service 
 private State state = outofServiceState;
 private int balance;
 private int withdrawAmt;

 public CashMachine(int balance) {
  hasCardState = new HasCardState(this);
  noCardState = new NoCardState(this);
  workingState = new WorkingState(this);
  outofServiceState = new OutofServiceState(this);
  this.balance = balance;
  if (balance > 0) {
   //if the balance is greather than zero then set the cashMachine to No Card State
   state = noCardState;
  }
 }

 public void setState(State state) {
  this.state = state;
 }

 public void insertCard() {
  state.insertCard();
 }

 public void ejectCard() {
  state.ejectCard();
 }

 public void enterAmount(int amount) {
  this.withdrawAmt = amount;
  state.enterAmount();
 }

 public void dispense() {
  state.dispense();
 }

 public State getHasCardState() {
  return hasCardState;
 }

 public void setHasCardState(State hasCardState) {
  this.hasCardState = hasCardState;
 }

 public State getNoCardState() {
  return noCardState;
 }

 public void setNoCardState(State noCardState) {
  this.noCardState = noCardState;
 }

 public State getWorkingState() {
  return workingState;
 }

 public void setWorkingState(State workingState) {
  this.workingState = workingState;
 }

 public State getOutofServiceState() {
  return outofServiceState;
 }

 public void setOutofServiceState(State outofServiceState) {
  this.outofServiceState = outofServiceState;
 }

 public State getState() {
  return state;
 }

 public void setBalance(int balance) {
  this.balance = balance;
 }

 public int getBalance() {
  return balance;
 }

 public int getWithdrawAmt() {
  return withdrawAmt;
 }

 public void printState() {
  System.out.println("Current State : " + this.state);
 }
 
}

CashMachineTestDrive.java

package com.statepattern.example;

public class CashMachineTestDrive {
 
 public static void main(String[] args) {
  CashMachine cashMachine = new CashMachine(100000);
  //printing current state using method printState
  cashMachine.printState();
  cashMachine.insertCard();
  cashMachine.printState();
  cashMachine.enterAmount(50000);
  cashMachine.printState();
  cashMachine.dispense();
  cashMachine.printState();
 }

}

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