A Comprehensive Guide to Java 8: Features and Benefits

4 min readSep 10, 2023

Java 8 marked a significant milestone in the evolution of the Java programming language. With a host of new features and enhancements, Java 8 revolutionized the way developers write code, making it more expressive, efficient, and user-friendly. In this comprehensive guide, we will explore Java 8 in-depth, covering its most notable features, benefits, and practical applications.

Let’s explore the important Java 8 features.

ForEach

In Java 8, the forEach method is a powerful addition to the Java Collections framework, allowing you to iterate over elements in a collection or stream and perform an action on each element.

List<String> names = Arrays.asList("Alice", "Bob", "Charlie");

// Using forEach on a List
names.forEach(name -> System.out.println("Hello, " + name));

Lambda Expressions

Lambda expressions are a cornerstone of Java 8’s foray into functional programming. They provide a concise way to define and use anonymous functions, enabling you to write more expressive and readable code.

// Traditional approach using an anonymous inner class
Runnable traditionalRunnable = new Runnable() {
    @Override
    public void run() {
        System.out.println("Hello from traditional Runnable!");
    }
};

// Using a lambda expression
Runnable lambdaRunnable = () -> {
    System.out.println("Hello from lambda Runnable!");
};

Functional Interfaces

A functional interface in Java is an interface that contains exactly one abstract method. It’s important to note that it can have multiple default or static methods, but it must have only one unimplemented (abstract) method. This single abstract method is often referred to as the “functional method” or “SAM” (Single Abstract Method). Functional interfaces are sometimes also called “SAM interfaces.”

@FunctionalInterface
interface Calculator {
    int calculate(int a, int b); // Functional method

    default void logResult(int result) {
        System.out.println("Result: " + result);
    }
}

In the above example, Calculator is a functional interface with a single abstract method calculate that takes two integers and returns an integer. It also includes a default method logResult with a concrete implementation.

Functional interfaces are closely associated with lambda expressions, as lambda expressions provide a concise way to implement the single abstract method of a functional interface. Here’s an example of using a lambda expression with a functional interface:

Calculator addition = (a, b) -> a + b;
int sum = addition.calculate(5, 3); // Using the lambda expression

In this example, a lambda expression is used to implement the calculate method of the Calculator functional interface, performing addition. This allows for a more compact and readable code compared to creating an anonymous inner class.

Stream API

The Stream API is a cornerstone of Java 8, providing a new way to work with sequences of data. Streams enable developers to process data in a functional style, facilitating operations like mapping, filtering, and reducing.

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
int sum = numbers.stream()
    .filter(n -> n % 2 == 0)
    .mapToInt(Integer::intValue)
    .sum();

Please visit the below links for better understanding of Stream API.

Java 8 Stream

Java 8 Stream continues…

Stream: More APIs

Stream: Terminal and Non-Terminal Operations

Parallel Streams in Java 8

flatMap in Stream

Optional Class

The Optional class addresses the problem of null values in Java. It promotes safer code by encapsulating the possibility of null in an object, helping to prevent null pointer exceptions.

Optional<String> optionalName = Optional.ofNullable(getName());
optionalName.ifPresent(name -> System.out.println("Hello, " + name));

Default and Static Methods in Interfaces

Java 8 introduced the ability to define default and static methods in interfaces.

Default methods provide backward compatibility to existing codebases when new methods are added to interfaces.

Static methods in interfaces allow developers to define utility methods that are associated with an interface, making it more versatile.

interface MyInterface {
    void methodA();

    default void methodB() {
        // Default implementation
    }

    // Static method
    static void staticMethod() {
        System.out.println("This is a static method in MyInterface.");
    }
}

Method References

Method references offer a concise way to refer to methods or constructors without invoking them. They can be used in conjunction with lambdas and functional interfaces, reducing boilerplate code.

import java.util.Arrays;
import java.util.List;
import java.util.function.Consumer;

class Person {
    void greet() {
        System.out.println("Hello, World!");
    }
}

public class MethodReferenceExample {
    public static void main(String[] args) {
        List<Person> people = Arrays.asList(new Person(), new Person());

        // Lambda expression
        Consumer<Person> lambda = person -> person.greet();

        // Instance method reference
        Consumer<Person> reference = Person::greet;

        people.forEach(reference);
    }
}

The java.time Package (Date and Time API)

The java.time package, also known as the Date and Time API, addresses the long-standing issues with date and time handling in Java. It provides immutable classes for representing dates, times, durations, and more.

LocalDate today = LocalDate.now();
LocalDate futureDate = today.plusDays(7);

Metaspace

Metaspace is a new memory space which has replaced PermGen.

Please visit Metaspace for more details.

StringJoiner

StringJoiner is a utility introduced in Java 8, serving the purpose of concatenating strings with a specified delimiter.

import java.util.StringJoiner;

public class StringJoinerExample {
    public static void main(String[] args) {
        // Create a StringJoiner with a delimiter
        StringJoiner joiner = new StringJoiner(", ");

        // Add elements to the joiner
        joiner.add("Apple");
        joiner.add("Banana");
        joiner.add("Cherry");

        // Convert the joiner to a single string
        String fruits = joiner.toString();

        // Print the result
        System.out.println("Fruits: " + fruits);
    }
}

// Output
Fruits: Apple, Banana, Cherry

Please visit StringJoiner for more information.

Conclusion

In this comprehensive guide, we’ve explored the key features of Java 8, their benefits, and practical use cases. Java 8’s embrace of functional programming and enhanced developer productivity have made it a valuable tool for modern software development.