Template Method

It defines the skeleton of an algorithm in a base class, allowing subclasses to override specific steps of the algorithm without changing its overall structure. This pattern is useful when you have a common algorithm that can be implemented in different ways by subclasses.

Structure

• Abstract Class: Contains the template method that defines the algorithm's structure and may include some abstract methods that subclasses must implement.
• Concrete Classes: Subclasses that implement the abstract methods defined in the base class, providing specific behavior for those steps.

Example

// Template Interface
interface Meal {
    // Template method
    default void prepareMeal() {
        gatherIngredients(); // Step 1: Gather ingredients
        cook();              // Step 2: Cooking
        serve();             // Step 3: Serving
    }

    // Method signatures for specific steps
    void gatherIngredients();
    void cook();

    // Default method for serving the meal
    default void serve() {
        System.out.println("Serving the meal.");
    }
}

// Concrete Class for preparing a Pasta dish
class Pasta implements Meal {
    @Override
    public void gatherIngredients() {
        System.out.println("Gathering ingredients for Pasta: pasta, tomato sauce, cheese.");
    }

    @Override
    public void cook() {
        System.out.println("Cooking Pasta: boiling pasta and adding sauce.");
    }
}

// Concrete Class for preparing a Salad dish
class Salad implements Meal {
    @Override
    public void gatherIngredients() {
        System.out.println("Gathering ingredients for Salad: lettuce, tomatoes, cucumber, dressing.");
    }

    @Override
    public void cook() {
        System.out.println("Tossing the Salad ingredients together.");
    }
}

// Client code
public class Main {
    public static void main(String[] args) {
        Meal pasta = new Pasta();
        pasta.prepareMeal(); // Prepare Pasta

        System.out.println(); // New line for separation

        Meal salad = new Salad();
        salad.prepareMeal(); // Prepare Salad
    }
}