Java Example
order/Order.java
package refactoring_guru.strategy.example.order;
import refactoring_guru.strategy.example.strategies.PayStrategy;
/**
* Order class. Doesn't know the concrete payment method (strategy) user has
* picked. It uses common strategy interface to delegate collecting payment data
* to strategy object. It can be used to save order to database.
*/
public class Order {
private int totalCost = 0;
private boolean isClosed = false;
public void processOrder(PayStrategy strategy) {
strategy.collectPaymentDetails();
// Here we could collect and store payment data from the strategy.
}
public void setTotalCost(int cost) {
this.totalCost += cost;
}
public int getTotalCost() {
return totalCost;
}
public boolean isClosed() {
return isClosed;
}
public void setClosed() {
isClosed = true;
}
}strategies
strategies/CreditCard.java
package refactoring_guru.strategy.example.strategies;
/**
* Dummy credit card class.
*/
public class CreditCard {
private int amount;
private String number;
private String date;
private String cvv;
CreditCard(String number, String date, String cvv) {
this.amount = 100_000;
this.number = number;
this.date = date;
this.cvv = cvv;
}
public void setAmount(int amount) {
this.amount = amount;
}
public int getAmount() {
return amount;
}
}strategies/PayByCreditCard.java
package refactoring_guru.strategy.example.strategies;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
/**
* Concrete strategy. Implements credit card payment method.
*/
public class PayByCreditCard implements PayStrategy {
private final BufferedReader READER = new BufferedReader(new InputStreamReader(System.in));
private CreditCard card;
/**
* Collect credit card data.
*/
@Override
public void collectPaymentDetails() {
try {
System.out.print("Enter the card number: ");
String number = READER.readLine();
System.out.print("Enter the card expiration date 'mm/yy': ");
String date = READER.readLine();
System.out.print("Enter the CVV code: ");
String cvv = READER.readLine();
card = new CreditCard(number, date, cvv);
// Validate credit card number...
} catch (IOException ex) {
ex.printStackTrace();
}
}
/**
* After card validation we can charge customer's credit card.
*/
@Override
public boolean pay(int paymentAmount) {
if (cardIsPresent()) {
System.out.println("Paying " + paymentAmount + " using Credit Card.");
card.setAmount(card.getAmount() - paymentAmount);
return true;
} else {
return false;
}
}
private boolean cardIsPresent() {
return card != null;
}
}strategies/PayByPayPal.java
package refactoring_guru.strategy.example.strategies;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;
/**
* Concrete strategy. Implements PayPal payment method.
*/
public class PayByPayPal implements PayStrategy {
private static final Map<String, String> DATA_BASE = new HashMap<>();
private final BufferedReader READER = new BufferedReader(new InputStreamReader(System.in));
private String email;
private String password;
private boolean signedIn;
static {
DATA_BASE.put("amanda1985", "amanda@ya.com");
DATA_BASE.put("qwerty", "john@amazon.eu");
}
/**
* Collect customer's data.
*/
@Override
public void collectPaymentDetails() {
try {
while (!signedIn) {
System.out.print("Enter the user's email: ");
email = READER.readLine();
System.out.print("Enter the password: ");
password = READER.readLine();
if (verify()) {
System.out.println("Data verification has been successful.");
} else {
System.out.println("Wrong email or password!");
}
}
} catch (IOException ex) {
ex.printStackTrace();
}
}
private boolean verify() {
setSignedIn(email.equals(DATA_BASE.get(password)));
return signedIn;
}
/**
* Save customer data for future shopping attempts.
*/
@Override
public boolean pay(int paymentAmount) {
if (signedIn) {
System.out.println("Paying " + paymentAmount + " using PayPal.");
return true;
} else {
return false;
}
}
private void setSignedIn(boolean signedIn) {
this.signedIn = signedIn;
}
}strategies/PayStrategy.java
package refactoring_guru.strategy.example.strategies;
/**
* Common interface for all strategies.
*/
public interface PayStrategy {
boolean pay(int paymentAmount);
void collectPaymentDetails();
}
Demo.java
package refactoring_guru.strategy.example;
import refactoring_guru.strategy.example.order.Order;
import refactoring_guru.strategy.example.strategies.PayByCreditCard;
import refactoring_guru.strategy.example.strategies.PayByPayPal;
import refactoring_guru.strategy.example.strategies.PayStrategy;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;
/**
* World first console e-commerce application.
*/
public class Demo {
private static Map<Integer, Integer> priceOnProducts = new HashMap<>();
private static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
private static Order order = new Order();
private static PayStrategy strategy;
static {
priceOnProducts.put(1, 2200);
priceOnProducts.put(2, 1850);
priceOnProducts.put(3, 1100);
priceOnProducts.put(4, 890);
}
public static void main(String[] args) throws IOException {
while (!order.isClosed()) {
int cost;
String continueChoice;
do {
System.out.print("Please, select a product:" + "\n" +
"1 - Mother board" + "\n" +
"2 - CPU" + "\n" +
"3 - HDD" + "\n" +
"4 - Memory" + "\n");
int choice = Integer.parseInt(reader.readLine());
cost = priceOnProducts.get(choice);
System.out.print("Count: ");
int count = Integer.parseInt(reader.readLine());
order.setTotalCost(cost * count);
System.out.print("Do you wish to continue selecting products? Y/N: ");
continueChoice = reader.readLine();
} while (continueChoice.equalsIgnoreCase("Y"));
if (strategy == null) {
System.out.println("Please, select a payment method:" + "\n" +
"1 - PalPay" + "\n" +
"2 - Credit Card");
String paymentMethod = reader.readLine();
// Client creates different strategies based on input from user,
// application configuration, etc.
if (paymentMethod.equals("1")) {
strategy = new PayByPayPal();
} else {
strategy = new PayByCreditCard();
}
}
// Order object delegates gathering payment data to strategy object,
// since only strategies know what data they need to process a
// payment.
order.processOrder(strategy);
System.out.print("Pay " + order.getTotalCost() + " units or Continue shopping? P/C: ");
String proceed = reader.readLine();
if (proceed.equalsIgnoreCase("P")) {
// Finally, strategy handles the payment.
if (strategy.pay(order.getTotalCost())) {
System.out.println("Payment has been successful.");
} else {
System.out.println("FAIL! Please, check your data.");
}
order.setClosed();
}
}
}
}Please, select a product:
1 - Mother board
2 - CPU
3 - HDD
4 - Memory
1
Count: 2
Do you wish to continue selecting products? Y/N: y
Please, select a product:
1 - Mother board
2 - CPU
3 - HDD
4 - Memory
2
Count: 1
Do you wish to continue selecting products? Y/N: n
Please, select a payment method:
1 - PalPay
2 - Credit Card
1
Enter the user's email: user@example.com
Enter the password: qwerty
Wrong email or password!
Enter user email: amanda@ya.com
Enter password: amanda1985
Data verification has been successful.
Pay 6250 units or Continue shopping? P/C: p
Paying 6250 using PayPal.
Payment has been successful.