How Upgrading from Java 8 to Java 21 Transformed My Coding Workflow

As a Java developer who used Java 8 for years, I was satisfied with its stability and features, but upgrading to Java 17 and then Java 21 dramatically changed my coding style.

Why I Stuck with Java 8 for So Long

I stayed on Java 8 because it was stable, widely adopted, and met enterprise needs. Upgrading felt not worth the effort until a personal project pushed me to try newer versions. Joining a team using Java 17+ and working with Java 21 showed the difference.

What Prompted Me to Explore Java 21

I wanted more:

Reduced boilerplate for better readability.

Simpler multithread management with more efficient methods.

Long‑term support (LTS) of Java 17 and 21 gave confidence for production.

These reasons led me to explore Java 21, quickly realizing it would greatly improve my coding life.

Features That Changed My Daily Java Work

Below are the features that had a noticeable impact.

var (Java 10)

Type inference reduces redundant declarations.

// Java 8
Map<String, List<String>> data = new HashMap<>();

// Java 10+
var data = new HashMap<String, List<String>>(); // more concise, still strongly typed

var cuts unnecessary type declarations, keeping code tidy.

Text Blocks (Java 13+)

They saved me hours when handling SQL and JSON.

// Java 8
String query = "SELECT * FROM users WHERE status = 'active'
" +
               "ORDER BY created_at DESC";

// Java 15+
String query = """
    SELECT * FROM users WHERE status = 'active'
    ORDER BY created_at DESC
    """;

Text blocks make multiline strings 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 make code more compact and safer.

Records (Java 14/16)

Eliminate boilerplate for immutable data carriers.

// Java 8
public class User {
    private final String name;
    private final int age;
    // constructor, getters, etc.
}

// Java 16+
record User(String name, int age) {}

Records remove boilerplate and simplify immutable class creation.

Pattern Matching for instanceof (Java 16)

No repeated casts.

// 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 reduces boilerplate and improves readability.

Virtual Threads (Java 21 – preview)

A breakthrough for concurrency; creating thousands of lightweight threads becomes trivial.

// Java 8: heavyweight thread
new Thread(() -> handleRequest()).start();

// Java 21: lightweight virtual thread
Thread.startVirtualThread(() -> handleRequest());

Virtual threads open opportunities for highly scalable I/O‑bound applications.

What Stayed the Same – And That’s Good

Despite new features, some things remain unchanged:

Java is still Java; the core language feels familiar.

The JVM remains rock‑solid; most existing libraries and tools work “as expected”.

My IDE (IntelliJ) quickly adapts to new features and provides solid support.

These factors help ensure a smooth transition to newer Java versions.

Challenges I Faced

During the upgrade I encountered challenges such as:

Updating build tools and plugins (e.g., Gradle).

Replacing libraries that used deprecated sun.* packages.

Unlearning Java 8 habits, especially around multithreading and concurrency.

These issues were solvable with a bit of research.

Conclusion – Is It Worth Upgrading?

If you’re still on Java 8, upgrading is definitely worthwhile. Java 21 brings performance gains, cleaner and more expressive code, and aligns with modern development practices. You don’t need to relearn Java; you just get to write better Java.

Now It’s Your Turn

Have you upgraded to Java 21? Share your experience in the comments or on Twitter/LinkedIn.