Strategy Design Pattern

package org.example;

public interface Strategy {

    void actionCommand();

}

package org.example;

public class AggressiveStrategy implements Strategy {

    @Override
    public void actionCommand() {
        System.out.println("Aggressive strategy. Find and kill opponent.");
    }

}

package org.example;

public class DefensiveStrategy implements Strategy {

    @Override
    public void actionCommand() {
        System.out.println("Defensive strategy. Protect self and teammates.");
    }

}

package org.example;

public class Player {

    Strategy strategy;
    String type;

    public Player(String type) {
        this.type = type;
    }

    public void setStrategy(Strategy strategy) {
        this.strategy = strategy;
    }

    public void action() {
        System.out.println("Player: " + this.type);
        strategy.actionCommand();
    }

} 

Another example:

package org.example.example2;

public interface PaymentStrategy {

    void pay(double amount);

}

package org.example.example2;

public class PayPalPayment implements PaymentStrategy {

    @Override
    public void pay(double amount) {
        System.out.println("Оплачено " + amount + " через PayPal.");
    }

}

package org.example.example2;

public class CryptoPayment implements PaymentStrategy {

    @Override
    public void pay(double amount) {
        System.out.println("Оплачено " + amount + " криптовалютой.");
    }

}

package org.example.example2;

public class CreditCardPayment implements PaymentStrategy {

    @Override
    public void pay(double amount) {
        System.out.println("Оплачено " + amount + " с помощью кредитной карты.");
    }

}

package org.example.example2;

public class PaymentContext {

    private PaymentStrategy paymentStrategy;

    public void setPaymentStrategy(PaymentStrategy paymentStrategy) {
        this.paymentStrategy = paymentStrategy;
    }

    public void executePayment(double amount) {
        if (paymentStrategy == null) {
            throw new IllegalStateException("Стратегия оплаты не установлена!");
        }
        paymentStrategy.pay(amount);
    }

}

package org.example.example2;

public class Main {

    public static void main(String[] args) {
        PaymentContext context = new PaymentContext();

        context.setPaymentStrategy(new CreditCardPayment());
        context.executePayment(100.0);

        context.setPaymentStrategy(new PayPalPayment());
        context.executePayment(50.0);

        context.setPaymentStrategy(new CryptoPayment());
        context.executePayment(200.0);

    }

}

Using Strategy and Factory together:

package org.example.example2;

public class PaymentStrategyFactory {

    public static PaymentStrategy getPaymentStrategy(String type) {
        switch (type.toLowerCase()) {
            case "card":
                return new CreditCardPayment();
            case "paypal":
                return new PayPalPayment();
            case "crypto":
                return new CryptoPayment();
            default:
                throw new IllegalArgumentException("Неизвестный способ оплаты: " + type);
        }
    }

}

package org.example.example2;

public class StrategyFactoryExample {

    public static void main(String[] args) {
        PaymentStrategy paymentStrategy = PaymentStrategyFactory.getPaymentStrategy("paypal");
        paymentStrategy.pay(100.0);
    }
    
}