Java design pattern template method pattern analysis

The template method pattern is a behavioral design pattern that defines the skeleton of the algorithm, and some steps are implemented by subclasses. (1) It contains abstract classes (defining the skeleton) and concrete classes (implementing specific steps). (2) Abstract classes define public operations and hook methods. (3) Concrete classes override hook methods to customize behavior. (4) Advantages include reusability, flexibility, and scalability. (5)Limitations include complexity and performance overhead.

Java Design Pattern Template Method Pattern

Introduction

Template Method Pattern It is a behavioral design pattern that defines a skeleton of operations and defers some steps to subclasses. This pattern allows subclasses to customize specific steps of an algorithm without changing the overall structure of the algorithm.

Structure

The template method pattern contains the following main roles:

• ##Abstract class (Abstract):Definition algorithm A skeleton, including public operations and optional hook methods.
• Concrete class (Concrete): Implement specific steps of the algorithm and override hook methods to customize behavior.

Code Example

// 抽象类
abstract class AbstractClass {
    public void execute() {
        preProcess();
        process();
        postProcess();
    }

    protected abstract void preProcess();

    protected abstract void process();

    protected abstract void postProcess();
}

// 具体类
class ConcreteClass1 extends AbstractClass {

    @Override
    protected void preProcess() {
        System.out.println("Performing pre-processing...");
    }

    @Override
    protected void process() {
        System.out.println("Performing processing...");
    }

    @Override
    protected void postProcess() {
        System.out.println("Performing post-processing...");
    }
}

// 具体类
class ConcreteClass2 extends AbstractClass {

    @Override
    protected void preProcess() {
        System.out.println("Performing pre-processing for ConcreteClass2...");
    }

    @Override
    protected void process() {
        System.out.println("Performing processing for ConcreteClass2...");
    }

    @Override
    protected void postProcess() {
        System.out.println("Performing post-processing for ConcreteClass2...");
    }
}

// 实战案例
public class Main {
    public static void main(String[] args) {
        AbstractClass concreteClass1 = new ConcreteClass1();
        concreteClass1.execute();

        // 输出：
        // Performing pre-processing...
        // Performing processing...
        // Performing post-processing...

        System.out.println();
        AbstractClass concreteClass2 = new ConcreteClass2();
        concreteClass2.execute();

        // 输出：
        // Performing pre-processing for ConcreteClass2...
        // Performing processing for ConcreteClass2...
        // Performing post-processing for ConcreteClass2...
    }
}

Advantages

• Reusability: The template method pattern allows the skeleton of an algorithm to be reused, while subclasses can customize specific steps.
• Flexibility: Subclasses can customize the behavior of the algorithm as needed without affecting the parent class.
• Extensibility: It is easy to add new concrete classes to extend the algorithm.

Limitations

• Complexity: The structure of an algorithm can become complex, especially when there are many concrete classes hour.
• Performance: The call to the hook method may introduce additional overhead.

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