Template Method Design Pattern in Java

A parent class fixes the steps of an algorithm. Child classes fill in only the steps that are different.

Real life example

Making a hot drink: boil water, brew, pour. Only the brewing is different for tea and coffee.

When to use

Several classes follow the same steps but a few steps are different.

Complete Java example

Save this as Main.java, then run javac Main.java and java Main.

public class Main {
    public static void main(String[] args) {
        new Tea().prepare();      // Boil water, Steep tea leaves, Pour in cup
        new Coffee().prepare();   // Boil water, Drip coffee, Pour in cup
    }
}

abstract class Beverage {
    final void prepare() {                         // the template: fixed order
        boilWater();
        brew();
        pour();
    }
    void boilWater() { System.out.println("Boil water"); }
    void pour()      { System.out.println("Pour in cup"); }
    abstract void brew();                          // children must write this step
}

class Tea    extends Beverage { void brew() { System.out.println("Steep tea leaves"); } }
class Coffee extends Beverage { void brew() { System.out.println("Drip coffee"); } }

Output

Boil water
Steep tea leaves
Pour in cup
Boil water
Drip coffee
Pour in cup