3.1 Lesson Outcomes

After completing this lesson, learners will be able to:

• Create functional interfaces in Java.
• Pass objects to functions.
• Create objects using functions.
• Use Java Streams for data processing.
• Apply map operations to transform data.

3.2 Overview

Functional programming is a programming style that focuses on functions, immutability, and data transformation. Java supports functional programming through:

• lambda expressions,
• functional interfaces,
• streams,
• and built-in functional interfaces.

Functional programming is important in:

• enterprise software,
• data processing,
• automation,
• and scalable application development.

This lesson introduces learners to practical functional programming techniques in Java.

Understanding functional programming is important because it simplifies code and improves readability and maintainability.

PA0301 — Build Interfaces onto Object Classes

Functional interfaces contain a single abstract method.

Java Example:

@FunctionalInterface

interface Greeting {

void sayHello(String name);

}

class Student {

String name;

Student(String name) {

this.name = name;

}

}

public class InterfaceDemo {

public static void main(String[] args) {

Greeting g = (n) -> System.out.println(“Welcome, “ + n + “!”);

Student s = new Student(“Alice”);

g.sayHello(s.name);

}

}

Practical Activity

Learners must:

• create functional interfaces,
• apply lambda expressions,
• and connect interfaces to object classes.

PA0302 — Pass an Object to a Function

Objects can be passed to functions using functional interfaces.

Java Example:

import java.util.function.Consumer;

class Student {

String name;
int marks;

Student(String name, int marks) {

this.name = name;
this.marks = marks;

}

}

public class PassObject {

public static void main(String[] args) {

Student s1 = new Student(“John”, 85);

Consumer display = (s) ->

System.out.println(s.name + “ scored “ + s.marks);

display.accept(s1);

}

}

Practical Activity

Learners must:

• pass objects to functions,
• apply Consumer interfaces,
• and display object information.

PA0303 — Create an Object Using a Function

Functional interfaces can create objects dynamically.

Java Example:

import java.util.function.Supplier;

class Car {

String model;

Car(String model) {

this.model = model;

}

}

public class CreateObject {

public static void main(String[] args) {

Supplier carSupplier = () -> new Car(“Toyota Corolla”);

Car c1 = carSupplier.get();

System.out.println(“Created a car: “ + c1.model);

}

}

Practical Activity

Learners must:

• create objects using functions,
• apply Supplier interfaces,
• and display object information.

PA0304 — Squares of First 10 Numbers

Java Streams simplify mathematical operations.

Java Example:

import java.util.stream.IntStream;

public class Squares {

public static void main(String[] args) {

IntStream.rangeClosed(1, 10)

.map(n -> n * n)

.forEach(System.out::println);

}

}

Practical Activity

Learners must:

• use streams,
• generate mathematical outputs,
• and process numeric data.

PA0305 — Use map Operation

The map() function transforms data inside streams.

Java Example:

import java.util.Arrays;

import java.util.List;

import java.util.stream.Collectors;

public class MapExample {

public static void main(String[] args) {

List names = Arrays.asList(“john”, “mary”, “paul”);

List upperNames = names.stream()

.map(String::toUpperCase)

.collect(Collectors.toList());

System.out.println(upperNames);

}

}

Practical Activity

Learners must:

• apply map operations,
• transform collection data,
• and display updated values.

AK0301 — Functions and Principles of Functional Programming in Java

Functional Programming Feature — Function

Lambda Expressions — Simplify function creation
Streams — Process collections efficiently
map() — Transform data
Consumer — Accept objects without return values
Supplier — Create and supply objects

Practical Activity

Learners must:

• identify functional programming features,
• explain stream processing,
• and apply functional programming concepts.

AK0302 — Deeper Understanding of Thought Processes

Functional programming encourages:

• cleaner logic,
• immutability,
• less repetitive code,
• and structured data transformation.

Practical Activity

Learners must:

• explain functional programming benefits,
• compare programming approaches,
• and apply logical thinking processes.

IAC0301 — Expected Results with Functional Programming in Java are Achieved

Expected Results

• Functional interfaces are implemented correctly.
• Lambda expressions function correctly.
• Objects are passed successfully to functions.
• Streams process data correctly.
• map() operations transform values successfully.

3.5 Key Notes / Summary

• Functional programming focuses on functions and data transformation.
• Lambda expressions simplify Java code.
• Functional interfaces contain one abstract method.
• Streams process collections efficiently.
• map() transforms collection data.
• Consumer accepts objects.
• Supplier creates objects dynamically.