What’s New in Java 8

Java 8 (released March 2014) was the most transformative Java release in history. It introduced lambda expressions, the Stream API, Optional, the java.time package, and default methods in interfaces — fundamentally changing how Java developers write code.

If you’re still on Java 8 (many enterprises are), this chapter is your guide to its features. If you’re on a newer version, this chapter explains the foundation that everything since has built upon.

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Key Java 8 Features

1. Lambda Expressions

Before Java 8:

Collections.sort(names, new Comparator<String>() {
    @Override
    public int compare(String a, String b) {
        return a.compareTo(b);
    }
});

After Java 8:

Collections.sort(names, (a, b) -> a.compareTo(b));

Or even simpler with method references:

names.sort(String::compareTo);

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2. Stream API

Process collections declaratively:

List<String> longNames = names.stream()
    .filter(name -> name.length() > 5)
    .map(String::toUpperCase)
    .sorted()
    .collect(Collectors.toList());

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3. Optional

Eliminate NullPointerException:

Optional<String> name = Optional.ofNullable(getUserName());
String displayName = name.orElse("Anonymous");

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4. java.time API

Replace the broken java.util.Date:

LocalDate today = LocalDate.now();
LocalDate birthday = LocalDate.of(1990, Month.JANUARY, 15);
long age = ChronoUnit.YEARS.between(birthday, today);

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5. Default Methods in Interfaces

public interface Vehicle {
    default void honk() {
        System.out.println("Beep!");
    }
}

Interfaces can now have method implementations — enabling API evolution without breaking existing implementations.

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6. CompletableFuture

Asynchronous programming without callback hell:

CompletableFuture.supplyAsync(() -> fetchUserFromDB())
    .thenApply(user -> enrichUserProfile(user))
    .thenAccept(profile -> sendWelcomeEmail(profile));

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Why Java 8 Matters in 2026

Even though Java 21 is the latest LTS, Java 8 is still running in many enterprises. Understanding Java 8 features is essential because:

• They’re the foundation for all modern Java code
• Many libraries and frameworks require Java 8 as minimum
• Interview questions frequently focus on Java 8 features

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What’s Next?

In the next chapter, you’ll learn what Java 11 (the next LTS) added — var, new String methods, the HTTP Client, and more.