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Choosing the Right Pattern: Decoding Template Method and Strategy Pattern



Often times in software design, understanding and applying the right design patterns is crucial for creating robust and maintainable systems. Two such patterns, the Template Method and the Strategy Pattern, offer distinct approaches to software design, each with its unique strengths and applications. While the Template Method relies on inheritance to define a part of an algorithm’s structure, leaving some details to be implemented by subclasses, the Strategy Pattern leverages composition, allowing the behavior of an object to be changed at runtime by associating it with different strategies. This article provides a deep dive into both patterns, comparing and contrasting their structures, use cases, and best practices, empowering developers to make informed decisions in their software design process.

Understanding the Template Method

The Template Method pattern is a cornerstone in object-oriented design, exemplifying the principle of “defining the skeleton of an algorithm, leaving the details to be implemented by subclasses.” It’s a behavioral design pattern that encapsulates an algorithm within a method, structuring it so that certain steps can be altered, while the overall sequence remains unchanged. This approach is ideal for scenarios with a fixed procedure where individual steps may require different implementations. By leveraging inheritance, the Template Method enables subclasses to redefine or extend specific steps of an algorithm without altering its overall structure. This leads to a more streamlined, maintainable codebase, where common parts of an algorithm are centralized, reducing redundancy and enhancing scalability. It’s a powerful tool in the developer’s arsenal for creating flexible yet consistent algorithms within a software application.

Figure 1. Template Method Diagram

Also available in: SVG | PlantText

In this diagram, we observe a classic representation of the Template Method pattern using UML (Unified Modeling Language). The diagram illustrates three key classes: AbstractClass, ConcreteClass1, and ConcreteClass2.

  1. AbstractClass is an abstract class, signifying that it provides a template method called templateMethod(). This method is designed to outline an algorithm’s structure. Crucially, it includes two abstract operations: primitiveOperation1() and primitiveOperation2(). These operations are declared, but not defined, in AbstractClass, indicating that their specific implementations are deferred to subclasses.

  2. ConcreteClass1 and ConcreteClass2 are subclasses of AbstractClass. They provide concrete implementations for the abstract operations defined in AbstractClass. Both these classes implement primitiveOperation1() and primitiveOperation2(), filling in the algorithm’s steps that were left undefined by their superclass.

  3. The inheritance relationship is clearly denoted by the lines leading from ConcreteClass1 and ConcreteClass2 to AbstractClass, indicated with an open arrowhead. This represents that both ConcreteClass1 and ConcreteClass2 are extending AbstractClass, thereby inheriting its template method and fulfilling the contract by implementing the abstract operations.

This diagram effectively communicates the hierarchical and structural relationships central to the Template Method pattern, emphasizing the separation of algorithm structure from its specific steps, which is the essence of this design pattern.

Exploring the Strategy Pattern

In contrast, the Strategy Pattern is a behavioral design pattern that enables an object to change its behavior at runtime by encapsulating an algorithm within a class. It defines a family of algorithms, encapsulates each one, and makes them interchangeable. This pattern is ideal for situations where multiple versions of an algorithm are required.

Figure 2. Strategy Pattern Diagram

Also available in: SVG | PlantText

In this diagram, the structure of the Strategy Pattern is depicted using UML notation. The diagram demonstrates the interaction between several classes and an interface that collectively embody the Strategy Pattern.

  1. At the heart of the diagram is the Context class. This class has a composition relationship with the Strategy interface, indicated by a solid line with a diamond on the Context end. The Context class contains a reference to a Strategy object (-strategy: Strategy), allowing it to utilize different strategies interchangeably. The constructor Context(strategy: Strategy) is used to inject a specific strategy, and the method executeStrategy(): void delegates the execution to the current Strategy object.

  2. The Strategy interface is critical in this pattern. It declares a method executeAlgorithm(): void, which is the common interface for all concrete strategies. This interface allows the Context class to interact with different strategies through a common interface, enabling runtime flexibility.

  3. ConcreteStrategyA and ConcreteStrategyB are classes that implement the Strategy interface. Each provides its own implementation of the executeAlgorithm(): void method. These classes represent different algorithms or behaviors that can be plugged into the Context class.

  4. The relationship between the Strategy interface and its concrete implementations (ConcreteStrategyA and ConcreteStrategyB) is depicted with dashed lines and open arrowheads. This represents the implementation of the interface by these concrete classes.

Overall, this UML diagram effectively communicates the essence of the Strategy Pattern: enabling an object to change its behavior at runtime by switching out different implementations of an interface. It highlights the decoupling of algorithm implementation from the context using it, promoting flexible and interchangeable behavior within software design.

Use Cases and Practical Applications

The Template Method and the Strategy Pattern are both powerful in their respective scenarios. By considering the updated examples, we can better understand their practical applications in software development.

Use Cases for Template Method: Building Construction Process

In the context of a building construction process, the Template Method pattern is perfectly suited. It defines the generic steps involved in constructing a building, such as laying the foundation, building the structure, installing the roof, and painting. However, the specifics of each step can vary depending on the type of building (e.g., Residential or Commercial).

In this example, the Template Method pattern is used to define the general steps for building construction, while allowing different types of buildings to implement specific details.

abstract class BuildingConstruction {
    // Template method
    final void build() {

    // Default implementations
    void layFoundation() {
        System.out.println("Foundation laid.");

    void paint() {
        System.out.println("Building painted.");

    // Steps to be implemented by subclasses
    abstract void buildStructure();
    abstract void installRoof();

class ResidentialBuilding extends BuildingConstruction {
    void buildStructure() {
        System.out.println("Building residential structure.");

    void installRoof() {
        System.out.println("Installing residential roof.");

class CommercialBuilding extends BuildingConstruction {
    void buildStructure() {
        System.out.println("Building commercial structure.");

    void installRoof() {
        System.out.println("Installing commercial roof.");

// Usage
public class Main {
    public static void main(String[] args) {
        BuildingConstruction residential = new ResidentialBuilding();

        BuildingConstruction commercial = new CommercialBuilding();

This approach demonstrates how a fixed sequence of steps in an algorithm (building construction process) can be efficiently managed while allowing for variability in certain steps, maintaining consistency and reducing redundancy.

Use Cases for Strategy Pattern: Data Compression

The Strategy Pattern is exemplified in the data compression example. Different compression algorithms (e.g., ZIP, RAR) are encapsulated as strategy classes, allowing them to be interchangeably used by the context class (CompressionContext).

In this example, the Strategy Pattern is used to define different data compression strategies (e.g., ZIP, RAR) that can be interchanged dynamically.

// Strategy interface
interface CompressionStrategy {
    void compress(String file);

// Concrete strategies
class ZipCompressionStrategy implements CompressionStrategy {
    public void compress(String file) {
        System.out.println("Compressing " + file + " using ZIP.");

class RarCompressionStrategy implements CompressionStrategy {
    public void compress(String file) {
        System.out.println("Compressing " + file + " using RAR.");

// Context class
class CompressionContext {
    private CompressionStrategy strategy;

    public void setCompressionStrategy(CompressionStrategy strategy) {
        this.strategy = strategy;

    public void createArchive(String file) {

// Usage
public class Main {
    public static void main(String[] args) {
        CompressionContext ctx = new CompressionContext();
        ctx.setCompressionStrategy(new ZipCompressionStrategy());
        ctx.setCompressionStrategy(new RarCompressionStrategy());

This pattern shines in scenarios where multiple algorithms or behaviors need to be dynamically selected and interchanged. It’s ideal for situations where operational flexibility and the ability to easily switch between different algorithms at runtime are required.

Both patterns, through these examples, demonstrate their unique strengths and use cases. The Template Method is ideal for scenarios with a fixed procedure and customizable steps, while the Strategy Pattern excels in situations that demand interchangeable, dynamic algorithm selection. Understanding these differences allows developers to choose the most appropriate pattern based on their project’s specific requirements.

Delineating Template Method and Strategy Pattern

In software architecture, discerning when to employ the Template Method versus the Strategy Pattern is crucial, as each serves distinct roles in managing algorithms and behaviors within applications.

Template Method stands as a design pattern that carves out the framework of an algorithm in a parent class while deferring specific steps to its subclasses. This pattern is particularly beneficial in situations where the overall sequence of an algorithm remains consistent, yet certain segments within that sequence necessitate variation.

Strategy Pattern, on the other hand, is a design paradigm that encapsulates a series of algorithms, allowing them to be mutually interchangeable. This pattern is especially suited for circumstances where the flexibility to switch between distinct algorithms at runtime is desired.

Fundamental Distinctions:

Guidelines for Selection:

Grasping the essential characteristics of these patterns empowers developers to make strategic choices, ensuring that the selected design approach optimally aligns with the requirements for effective and adaptable software development.


In conclusion, both the Template Method and Strategy Pattern are essential tools in the software developer’s toolkit, each serving distinct purposes in design architecture. The Template Method, with its reliance on inheritance, is ideal for scenarios where an algorithm’s overarching structure is fixed, but certain steps require variability. On the other hand, the Strategy Pattern, leveraging composition, offers the flexibility to swap entire algorithms, catering to situations demanding dynamic behavior changes at runtime. Understanding the nuances and appropriate contexts for each pattern is crucial for effective software design, ensuring the development of robust, flexible, and maintainable software solutions. Ultimately, the choice between these patterns hinges on the specific needs and constraints of your project, underscoring the importance of thoughtful design in software engineering.

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