What is Java 8 ? and Why it is so popular version ?

Java 8, released in March 2014, is one of the most significant versions of Java. It introduced major improvements in functional programming, performance, and API enhancements, making Java more concise and efficient.

1. Why is Java 8 So Popular?

Java 8 is widely used because of:
Functional programming (Lambda Expressions, Streams)
Parallel processing (Faster execution with Streams & ForkJoinPool)
Better memory management (Garbage Collector improvements)
New Date & Time API (More efficient than java.util.Date)
Default & Static Methods in Interfaces (More flexible API design)
Improved Performance & Security

2. Key Features of Java 8

1. Lambda Expressions (Functional Programming)

Lambda expressions allow us to write concise anonymous functions.

Before Java 8 (Using Anonymous Class)

new Thread(new Runnable() {
    @Override
    public void run() {
        System.out.println("Hello, Java 7!");
    }
}).start();

With Java 8 (Using Lambda Expression)

new Thread(() -> System.out.println("Hello, Java 8!")).start();

Note : Lambda expressions reduce boilerplate code and improve readability.

2. Functional Interfaces & `@FunctionalInterface`

A Functional Interface is an interface with only one abstract method.
Examples: Runnable, Callable, Comparator, Predicate, Function.

Custom Functional Interface Example:

@FunctionalInterface
interface Greeting {
    void sayHello();
}

public class LambdaExample {
    public static void main(String[] args) {
        Greeting g = () -> System.out.println("Hello, Java 8!");
        g.sayHello();
    }
}

Note : Functional interfaces enable functional programming in Java.

3. Stream API (Processing Collections Efficiently)

The Stream API helps in performing operations like filtering, mapping, and reducing without modifying the original collection.

Example: Filtering and Sorting a List

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class StreamExample {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Alice", "Bob", "John", "Charlie");

        List<String> sortedNames = names.stream()
                                        .filter(name -> name.startsWith("A"))
                                        .sorted()
                                        .collect(Collectors.toList());

        System.out.println(sortedNames); // Output: [Alice]
    }
}

Note : Streams make Java more expressive and efficient for data processing.

List of Popular Java Stream API Methods to Learn:

4. Default & Static Methods in Interfaces

Java 8 introduced default methods inside interfaces to allow method implementation without breaking existing code.

Example: Default Method in Interface

interface Vehicle {
    default void start() {
        System.out.println("Vehicle is starting...");
    }
}

class Car implements Vehicle {}

public class DefaultMethodExample {
    public static void main(String[] args) {
        Car myCar = new Car();
        myCar.start(); // Output: Vehicle is starting...
    }
}

Note : Interfaces can now evolve without breaking backward compatibility.

5. New `java.time` API (Better Date/Time Handling)

The old Date and Calendar classes were replaced with the more powerful java.time package.

Example: Using LocalDateTime

import java.time.LocalDateTime;

public class DateTimeExample {
    public static void main(String[] args) {
        LocalDateTime now = LocalDateTime.now();
        System.out.println("Current Date & Time: " + now);
    }
}

Note : More reliable, immutable, and thread-safe date/time handling.

6. Optional Class (Avoid `NullPointerException`)

The Optional class helps avoid null checks.

Example: Using Optional

import java.util.Optional;

public class OptionalExample {
    public static void main(String[] args) {
        Optional<String> name = Optional.ofNullable(null);
        System.out.println(name.orElse("Default Name")); // Output: Default Name
    }
}

Note : Reduces NullPointerException risks in Java applications.

7. Improved Garbage Collection (G1 GC)

Java 8 introduced the G1 Garbage Collector, improving memory management.
Reduces stop-the-world pauses, improving performance.

3. Java 8 vs. Java 7 – Why Upgrade?

Feature	Java 7	Java 8
Lambda Expressions	No	Yes
Stream API	No	Yes
Functional Interfaces	No	Yes (`@FunctionalInterface`)
Default & Static Methods in Interfaces	No	Yes
New Date & Time API	No (`java.util.Date`)	Yes (`java.time.LocalDate`)
Optional Class (Avoid NullPointerException)	No	Yes
Parallel Streams	No	Yes

4. Performance Improvements in Java 8

Faster Stream Operations due to lazy evaluation.
Reduced memory usage with compact strings.
G1 Garbage Collector improves performance.
Faster Parallel Execution with ForkJoinPool.

5. Why Should You Learn Java 8?

Most enterprise applications use Java 8 (LTS version).
Lambda & Stream API reduce boilerplate code.
More expressive & functional programming style.
New Date & Time API makes handling dates easier.
Performance improvements & better memory management.

6. Java 8 in Real-World Applications

Spring Boot & Microservices heavily use Streams & Lambdas.
Big Data processing (Apache Spark, Hadoop) benefits from Parallel Streams.
REST APIs & Web Applications use Optional & DateTime APIs.

7. Where should i begin with :

1. Learn Basic and Advanced Interview Questions

2. Learn the Difference between Topics on Java 8

Java 8 is one of the biggest revolutions in Java, making it more concise, functional, and efficient. it’s time to upgrade in an Efficient way! .