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1. Strategy Pattern Overview

Using composition rather than inheritance

Strategy patten define a set of algorithms, encapsulate each of them and make then exchangable. And we could switch them at run time , decouple the algorithm with the place they are used

2. Why use strategy pattern?

• when we have a set of classes, they belong to same object, they should could a certain types of actions, but the detail would vary. Then we need a way to regulate they have such type of behaviors, and also differ them in a maintainable manner
• literaly composition over inheritance
• 其实主要还是在考虑代码的可扩展性，多考虑下如何应对可能的改动，Design Pattern整个就是为了应对改动来服务的，并不太需要神化，毕竟只是对于常见的一些应用场景的抽象，想要达到的目的也就是抽象出来，以后做的时候会在范式下，更专注在业务逻辑上的问题

3. Implementation

3.1 Interface

public interface IFlyBehavior {
    void fly();
}

public interface IQuackBehavior {
    void quack();
}

3.2 Implementation

public class Duck {
    IFlyBehavior flyBehavior;
    IQuackBehavior quackBehavior;

    public void fly() {
        flyBehavior.fly();
    }
    public void quack() {
        quackBehavior.quack();
    }
}

public class JetFly implements IFlyBehavior {
    @Override
    public void fly() {
        System.out.println("Jet Fly");
    }
}

public class SimplyFly implements IFlyBehavior {
    @Override
    public void fly() {
        System.out.println("Simple flying");
    }
}

public class LoudQuack implements IQuackBehavior {
    @Override
    public void quack() {
        System.out.println("Make noise!");
    }
}

public class NoQuack implements IQuackBehavior {
    @Override
    public void quack() {
        // do nothing, as no quack exist
    }
}

public class ToyDuck extends Duck {

    public ToyDuck(IFlyBehavior flyBehavior, IQuackBehavior quackBehavior) {
        this.flyBehavior = flyBehavior;
        this.quackBehavior = quackBehavior;
    }
}

3.3 Test

@GetMapping("/strategy")
    public String strategy() {
        Duck testDuck = new ToyDuck(new JetFly(), new LoudQuack());
        testDuck.fly();
        testDuck.quack();

        return "check the log";
    }

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