From Java 8 to Java 21: How the Evolution Changed My Developer Workflow

As a Java developer who spent years working with Java 8, I was comfortable with the stability and functionality it provided — lambda expressions, Streams and the java.time API felt like revolutionary improvements when they first arrived. But like many others, I stuck with Java 8 for years, not seeing the need to move on. That was, until I had the chance to work with Java 17 and eventually Java 21. In this post, I reflect on the features that truly changed the way I code and why it’s worth upgrading from Java 8 to Java 21.

Why I Stuck With Java 8 for So Long

I stuck with Java 8 for a long time because it just worked. It was stable, widely adopted and most importantly, it met the needs of enterprise projects. Newer versions came out, but transitioning wasn't always worth the effort — until my personal project pushed me to try something different. As I joined a team using Java 17+ and started working with Java 21 in real-world projects, I began to see just how much had changed.

What Pushed Me to Explore Java 21

I wanted more:

• Better readability with less boilerplate code.
• Easier concurrency management with a more efficient approach to multithreading.
• LTS (Long-Term Support) from Java 17 and 21, which gave me confidence in their stability for production environments.

These reasons led me to finally explore Java 21 and I quickly realized how much my coding life would improve.

The Features That Changed My Day-to-Day Java Life

Here are some standout features that significantly impacted my day-to-day work as a Java developer.

var (Java 10)

I never thought I’d care, but type inference really helped reduce noise:

// Java 8

Map<String, List<String>> data = new HashMap<>();

 // Java 10+

var data = new HashMap<String, List<String>>(); // Cleaner, still strongly typed.

var reduced unnecessary type declarations and made my code less cluttered.

Text Blocks (Java 13+)

This alone saved me hours when dealing with SQL and JSON:

// Java 8

String query = "SELECT * FROM users WHERE status = 'active'\n" +

               "ORDER BY created_at DESC";

 // Java 15+

String query = """

    SELECT * FROM users WHERE status = 'active'

    ORDER BY created_at DESC

    """;

Text blocks made multiline strings far more readable and maintainable.

Switch Expressions (Java 14)

More expressive and less error-prone:

// Java 8

switch (role) {

    case "ADMIN":

        permission = 3;

        break;

    case "USER":

        permission = 1;

        break;

    default:

        permission = 0;

}

 
// Java 14+

permission = switch (role) {

    case "ADMIN" -> 3;

    case "USER" -> 1;

    default -> 0;

};

Switch expressions made my code more compact and less error-prone.

Records (Java 14/16)

Sick of writing boilerplate DTOs? Records made it simple.

// Java 8

public class User {

    private final String name;

    private final int age;

 

    public User(String name, int age) {

        this.name = name;

        this.age = age;

    }

    public String getName() { return name; }

    public int getAge() { return age; }

}

 

// Java 16+

record User(String name, int age) {}; // Immutable and auto-generated methods by default.

Records eliminated boilerplate and simplified creating immutable classes.

Pattern Matching for instanceof (Java 16)

No more repetitive casting:

// Java 8

if (obj instanceof String) {

    String s = (String) obj;

    System.out.println(s.length());

}

 

// Java 16+

if (obj instanceof String s) {

    System.out.println(s.length());

}

Pattern matching reduced boilerplate and made my code more readable.

Virtual Threads (Java 21 — Preview)

This is a big deal for concurrency. Creating thousands of threads is now trivial and efficient:

// Java 8: Heavyweight threads

new Thread(() -> handleRequest()).start();

 // Java 21: Lightweight virtual thread

Thread.startVirtualThread(() -> handleRequest());

Virtual threads opened up opportunities for highly scalable I/O-intensive applications.

What Didn’t Change — and That’s a Good Thing

Despite all these new features, some things remained the same:

• Java is still Java. The core language felt familiar throughout.
• The JVM is rock-solid. Most of my existing libraries and tools "just worked."
• My IDE (IntelliJ) quickly adapted to newer features with solid support.

These elements helped ensure a smooth transition to newer versions of Java.

Challenges I Faced

While upgrading, I ran into a few challenges, such as:

• Updating build tools and plugins (e.g., Gradle).
• Libraries that used deprecated sun.* packages needed replacement.
• It took some time to unlearn habits from Java 8, especially around multithreading and concurrency.

But nothing was a dealbreaker and most issues were easily fixed with a bit of research.

Final Thoughts: Is It Worth Upgrading?

If you're still on Java 8, it’s absolutely worth upgrading. Java 21 offers more than just performance improvements — it’s cleaner, more expressive, and better suited for modern development practices. You don’t need to relearn Java; you just write it better.

Over to You

Have you upgraded to Java 21 yet? What was your experience like? Let me know in the comments or tag me on Twitter/LinkedIn if you’ve written your own upgrade journey!