Template Design pattern or Template Method Design pattern - Implementation [Coffee]

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What is the Template Method Design Pattern?

The Template Method Pattern is a behavioral design pattern that defines the skeleton of an algorithm in an abstract base class, allowing subclasses to redefine certain steps without altering the overall structure.

Think of making coffee: every coffee recipe follows a standard sequence — boiling water, brewing/adding coffee powder, adding milk, and adding sugar. While the steps are identical, the exact ingredients and quantities differ depending on whether you are preparing Bru Coffee or Nescafé.

The Real-World Coffee Preparation Analogy

In our example, we define an abstract class called CoffeeTemplate containing:

• Abstract Methods: boilWater(), addMilk(), addSugar(), and addCoffeePowder(). Subclasses implement these specific steps.
• Template Method: prepareCoffee(). This method executes the sequence of steps and is marked final so subclasses cannot alter the overall algorithm.

Java Implementation Breakdown

Here is how the core structure is laid out in code:

// Abstract Template Class
public abstract class CoffeeTemplate {

    // Template method defined as final
    public final void prepareCoffee() {
        boilWater();
        addMilk();
        addSugar();
        addCoffeePowder();
        System.out.println("Coffee is ready!\n");
    }

    public abstract void boilWater();
    public abstract void addMilk();
    public abstract void addSugar();
    public abstract void addCoffeePowder();
}

The concrete classes BruCoffee and NescafeCoffee extend CoffeeTemplate and specify the exact quantities and powder types. The client simply invokes prepareCoffee(), maintaining clean separation of concerns and eliminating code duplication.

Related Tutorials from Ram N Java

• 👉 Template Design Pattern or Template Method Design Pattern: Introduction
• 👉 Template Design Pattern or Template Method Design Pattern: Class diagram Explained
• 👉 Template Design Pattern or Template Method Design Pattern: Real-Time Example with Coffee Making

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Template Design pattern or Template Method Design pattern - Implementation [Coffee]

Template Design pattern or Template Method Design pattern - Implementation [Coffee] - Class Diagram

CoffeeTemplate.java

public abstract class CoffeeTemplate

{

/*

 *  prepareCoffee method is a template method,this method is final,so

 *  subclasses cannot override.

 */

public final void prepareCoffee()

{

boilWater();

addMilk();

addSugar();

addCoffeePowder();

System.out.println("Hot coffee ready.....");

}

public abstract void boilWater();

public abstract void addMilk();

public abstract void addSugar();

public abstract void addCoffeePowder();

}

BruCoffee.java

public class BruCoffee extends CoffeeTemplate

{

@Override

public void boilWater()

{

System.out.println("100 ml water boiled");

}

@Override

public void addMilk()

{

System.out.println("100 ml milk Added");

}

@Override

public void addSugar()

{

System.out.println("100 grams sugar Added");

}

@Override

public void addCoffeePowder()

{

System.out.println("10 grams Bru coffee powder Added");

}

}

NescafeCoffee.java

public class NescafeCoffee extends CoffeeTemplate

{

@Override

public void boilWater()

{

System.out.println("200 ml water boiled");

}

@Override

public void addMilk()

{

System.out.println("200 ml milk Added");

}

@Override

public void addSugar()

{

System.out.println("200 grams sugar Added");

}

@Override

public void addCoffeePowder()

{

System.out.println("20 grams Nescafe coffee powder Added");

}

}

CoffeeClient.java

public class CoffeeClient

{

public static void main( String[] args )

{

System.out.println("Bru coffee preparation\n");

CoffeeTemplate bruCoffee = new BruCoffee();

bruCoffee.prepareCoffee();

System.out.println("*******************************************");

System.out.println("Nescafe coffee preparation\n");

CoffeeTemplate NescafeCoffee = new NescafeCoffee();

NescafeCoffee.prepareCoffee();

}

}

Output

Bru coffee preparation

100 ml water boiled

100 ml milk Added

100 grams sugar Added

10 grams Bru coffee powder Added

Hot coffee ready.....

*******************************************

Nescafe coffee preparation

200 ml water boiled

200 ml milk Added

200 grams sugar Added

20 grams Nescafe coffee powder Added

Hot coffee ready.....

See also:

Template Design pattern or Template Method Design pattern - Introduction

Template Design pattern or Template Method Design pattern - Real Time Example [Coffee]

Template Design pattern or Template Method Design pattern - Real Time Example [Car]

Template Design pattern or Template Method Design pattern - Class Diagram

Template Design pattern or Template Method Design pattern - Implementation [Building a House]

Template Design pattern or Template Method Design pattern - KeyPoints

All Design Patterns Links