我正在尝试使用Java8实现下面代码段中的策略设计模式。是否寻找更好的实现方法？

我有以下服务实施：-

package Java8.controller;

import java.util.function.Function;

public class ServiceImpl implements ITicket {

    Function<Integer,Double> ticketCal;

    public ServiceImpl(Function<Integer,Double> ticketCal){
        this.ticketCal= ticketCal;
    }

    @Override
    public double calculateFare(int quantity) {
        return ticketCal.apply(quantity);
    }

}

---

我的问题是，这是否是将策略函数作为默认方法保存在界面中的正确方法？或者有更好的方法吗？

您在这里定义了一种策略。但您应该定义一个更能代表业务的通用接口，如：

public interface TicketStrategy {
    Double fare(final Integer quantity);
}

如果需要，您可以将其设置为功能界面：

@FunctionalInterface
public interface TicketStrategy {
    Double fare(final Integer quantity);
}

然后像以前一样实现：

public class TicketStrategies {

    public static final TicketStrategy VIP = noOfTickets -> noOfTickets * 400.00;
    public static final TicketStrategy RECLINER = noOfTickets-> noOfTickets * 200.00;
}

然后，您的主视图如下所示：

public static void main(String[] args) {
    ITicket ticketsVip = new ServiceImpl(RECLINER));
    System.out.println(ticketsVip.calculateFare(5));
}

public class TicketStrategyFactory {

    private static final Map<String, TicketStrategy> STRATEGIES;

    static {
        final HashMap<String, TicketStrategy> strategies = new HashMap<>();
        strategies.put("vip", TicketStrategies.VIP);
        strategies.put("recliner", TicketStrategies.RECLINER);
        STRATEGIES = Collections.unmodifiableMap(strategies);
    }

    public TicketStrategyFactory() {

    }

    public TicketStrategy create(String type) {
        TicketStrategy strategy = STRATEGIES.get(type);
        if (strategy == null) {
            throw new IllegalArgumentException("Unknown strategy " + type);
        }
        return strategy;
    }
}

public static void main(String[] args) {
    TicketStrategyFactory factory = new TicketStrategyFactory();
    ITicket ticketsVip = new ServiceImpl(factory.create("vip"));
    System.out.println(ticketsVip.calculateFare(5));
}

public class TicketStrategies {

    public static final TicketStrategy RECLINER = noOfTickets -> noOfTickets * 200.00;
    public static final TicketStrategy VIP = noOfTickets -> RECLINER.fare(noOfTickets) * 200;
}

您可以将其与工厂模式一起使用，如下所示：

public static void main(String[] args) {
    ITicket ticketsVip = new ServiceImpl(RECLINER));
    System.out.println(ticketsVip.calculateFare(5));
}

public class TicketStrategyFactory {

    private static final Map<String, TicketStrategy> STRATEGIES;

    static {
        final HashMap<String, TicketStrategy> strategies = new HashMap<>();
        strategies.put("vip", TicketStrategies.VIP);
        strategies.put("recliner", TicketStrategies.RECLINER);
        STRATEGIES = Collections.unmodifiableMap(strategies);
    }

    public TicketStrategyFactory() {

    }

    public TicketStrategy create(String type) {
        TicketStrategy strategy = STRATEGIES.get(type);
        if (strategy == null) {
            throw new IllegalArgumentException("Unknown strategy " + type);
        }
        return strategy;
    }
}

public static void main(String[] args) {
    TicketStrategyFactory factory = new TicketStrategyFactory();
    ITicket ticketsVip = new ServiceImpl(factory.create("vip"));
    System.out.println(ticketsVip.calculateFare(5));
}

public class TicketStrategies {

    public static final TicketStrategy RECLINER = noOfTickets -> noOfTickets * 200.00;
    public static final TicketStrategy VIP = noOfTickets -> RECLINER.fare(noOfTickets) * 200;
}

策略应该实现服务所需的抽象。在这种情况下，服务需要一个

函数

，因此策略将是

class ReclinerTicketStrategy implements Function<Integer,Double> {
    @Override
    public Double apply(Integer noOfTickets) {
        return noOfTickets * 200.0;
    }
}

类ReclinerTicketStrategy实现函数{
@凌驾
公共双应用（整数noOfTickets）{
返回方便面*200.0；
}
}

然后将服务实例化为，

ITicket RECLINERTICKE=new ServiceImpl（new ReclinerTicketStrategy（））

当然，如果不需要重用该策略，那么lambda就足够了

ITicket reclinerTicket=newServiceImpl（noOfTickets->noOfTickets*200.0）
它是否违反了OCP？比如说，如果我们想添加另一个策略，那么我们必须修改TicketStrategyFactory并执行类似策略的操作；并且在这门课上增加一个新的策略？把所有的策略放在同一个课堂策略中也是一个好主意吗？既然我们想添加任何新策略，我们就必须修改这个类？这是不是又一次违反了OCP？这是你获得想法的一个例子。但是，是的，你可以很容易地为工厂添加策略！你可以把这些策略放到其他地方！