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This article shows you what the strategic model in big data is, which is concise and easy to understand. It will definitely brighten your eyes. I hope you can get something through the detailed introduction of this article.

I remember in middle school, every time after the teacher commented on the test paper, he would say how many solutions there were for this question, and then write the first and second solutions on the blackboard. In fact, this situation is similar to today's situation, that is, the strategic model. What he said is that when there are multiple solutions to a problem, we can choose different algorithms or strategies according to different environments or conditions to complete this function.

First, understand the strategic model

In order to better understand this model, let's give another example. When we travel, there may be many ways to travel. For example, we can take trains, high-speed trains, airplanes and so on. No matter which mode of travel we use, the final destination is the same, that is, the result of choosing different ways is the same.

With this example, I believe you should have a basic understanding of his ideas. let's take a look at its formal concept introduction:

Define a series of algorithms, encapsulate each algorithm, and make them interchangeable

Second, implement the strategy model

The strategy pattern distinguishes the object itself from the operation rules, so our whole pattern is divided into three parts.

Context: the context in which we operate the policy, that is, we tourists. Abstract policy class (Strategy): abstraction of policy, abstract concrete policy class of travel mode (ConcreteStrategy): concrete policy implementation, concrete implementation of each travel mode.

Let's go through the code and then we can understand it very clearly.

Step 1: define an abstract policy interface

Interface TravelStrategy {

Public function travelAlgorithm ()

}

Step 2: specific policy class

/ / the first one: use the train

Public class TrainStrategy implements TravelStrategy {

@ Override

Public void travelStyle () {

System.out.println ("take the train.")

}

}

/ / second: use high-speed rail

Public class HighTrainStrategy implements TravelStrategy {

@ Override

Public void travelStyle () {

System.out.println ("take the high-speed rail.")

}

}

/ / third: the use of aircraft

Public class AirStrategy implements TravelStrategy {

@ Override

Public void travelStyle () {

System.out.println ("by plane...")

}

}

Step 3: environment class implementation

Public class Traveler {

/ / Travel Policy API

TravelStrategy travelStrategy

/ / set travel policy

Public void setTravelStrategy (TravelStrategy travelStrategy) {

This.travelStrategy = travelStrategy

}

/ / set the travel mode for the current user

Public void travelStyle () {

TravelStrategy.travelStyle ()

}

Public static void main (String [] args) {

Traveler traveler=new Traveler ()

/ / tourists set travel policies

/ / traveler.setTravelStrategy (new TrainStrategy ())

/ / traveler.setTravelStrategy (new HighTrainStrategy ())

/ / traveler.setTravelStrategy (new AirStrategy ())

/ / tourists travel

Traveler.travelStyle ()

}

}

Third, analyze the strategy mode 1. Why use the policy mode? Advantages of the policy model:

When we choose the travel mode before, we often use the if-else statement, that is, the user chooses B instead of A, which is too coupled and the code is bloated. With the policy mode, we can avoid this phenomenon.

The strategy pattern follows the opening and closing principle and realizes the decoupling of the code. It is also convenient to extend the new method, just inherit the policy interface.

Shortcoming

The client must know all the policy classes and decide which one to use

There are a lot of policy classes in the policy pattern.

When context uses these policy classes, these policy classes may not use some data because they inherit the policy interface, but they are still initialized.

2. What is the difference from other models? (1) the difference between state mode and state mode

The policy mode is only a conditional selection method, and the method is executed only once, while the state mode is constantly changing the execution method as the state changes. For example, for example, when we travel, we only need to choose one of the travel methods for the strategic mode, but the state mode is different. maybe we choose a train at location An and a plane at location B. choose different modes of travel according to different states.

(2) the difference between factory model and factory model

Factory pattern is a creative mode, which focuses on object creation and provides an interface for creating objects. Make the creation of the object independent of the specific user. Policy pattern is an object behavior pattern, which focuses on the encapsulation of behavior and algorithms. For another example, if we travel, we only need to choose one of the travel methods for the strategic mode, but the factory model is different. After you decide which travel plan, the factory will build the specific plan for you (the factory will buy the train ticket instead of you).

3. What is the usage scenario?

To be honest, for design patterns, the use of scenarios is just one or two examples, and if you can understand the case of our trip, you can basically choose it automatically when you encounter this situation. Let's not say it here.

OK, the strategy mode is relatively simple. In a word, there are several solutions to a problem, and we can choose one of them.

The above is what is the strategic model in big data. Have you learned the knowledge or skills? If you want to learn more skills or enrich your knowledge reserve, you are welcome to follow the industry information channel.

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