How Java Has Evolved: Java 8 to Java 21 Evolution

👋 Introduction

Java has been around for over 25 years and is still one of the most used programming languages in the world. Starting from Java 8, the language has seen many important changes that made it more powerful, readable, and modern. In this blog post, we’ll take a step-by-step journey from Java 8 to Java 21 evolution, explaining the major features in each version in simple terms.

How Java Has Evolved: Java 8 to Java 21 Evolution

🏁 Java 8 (2014): A Revolution in Java

Java 8 introduced many game-changing features:

🔹 Lambdas (→)

Lets you write functions in fewer lines.
Useful for writing clean and short code, especially when working with lists or collections.

list.forEach(item > System.out.println(item));

🔹 Streams API

Allows processing of data (like filtering, mapping, sorting) in a functional style.

List<string> names = people.stream()

.filter(p -> p.getAge() > 18)

.map(Person::getName)

.collect(Collectors.toList());

🔹 Optional

Helps avoid NullPointerException by handling missing values in a safe way.

🔹 Default Methods in Interfaces

You can now add default method implementations to interfaces without breaking existing code.

🔹 New Date & Time API

A much cleaner way to handle date and time than the old Date class.

🔄 Java 9–10–11: Cleaning Up and Simplifying

🧱 Java 9 – The Module System

Introduced JPMS (Java Platform Module System) for breaking large applications into manageable modules.
Useful for large-scale applications.

🧪 JShell (Java Shell)

A tool to test Java code quickly without writing full class files—great for beginners!

🔣 Java 10 – `var` Keyword

Introduced local variable type inference using var.

var name = "Java"; // Compiler figures out the type

🏷 Java 11 – A New LTS Release

Long-Term Support version (just like Java 8).
Brought useful string methods like:
- isBlank()
- lines()
- strip()
Removed some older APIs to clean up the language.

🚧 Java 12 to Java 17: Modernization Continues

🔁 Java 14 – Switch Expressions

You can now use switch like an expression that returns a value.

String result = switch (day) {

case MONDAY -> "Start of week";

default -> "Other day";

};

🔤 Java 15 – Text Blocks

Makes it easier to write multiline strings without \n or lots of quotes.

String html = "

Hello

</body></html>

📦 Java 16 – Records

A compact way to create classes for holding data.

1 2	record User(String name, int age) {}

Automatically creates constructor, toString(), equals(), and hashCode() methods.

🔐 Java 17 – Sealed Classes (LTS)

Allows you to restrict which classes can extend a class.

1 2	sealed class Shape permits Circle, Square {}

⚡ Java 18 to 20: Getting Ready for Big Changes

🌐 Java 18 – UTF-8 by Default

Java source files now use UTF-8 as the default encoding—better support for international text.

🧵 Java 19 – Virtual Threads (Preview)

A new way to create threads that are lighter and faster.
Great for high-performance applications like servers.

👪 Java 20 – Structured Concurrency (Preview)

A better way to manage multiple threads working together—improves readability and reliability.

🌟 Java 21 – A Modern Powerhouse

Released in 2023, Java 21 is packed with useful features:

🧵 Virtual Threads (Finalized)

Much lighter than traditional threads.
Makes it easy to write high-performance concurrent applications.

🔍 Record Patterns

Combines records and pattern matching for powerful, concise code.

if (obj instanceof User(String name, int age)) {

System.out.println(name + " is " + age + " years old.");

}

📜 Pattern Matching for `switch`

Makes switch smarter and more flexible.

switch (obj) {

case String s -> System.out.println("It's a string: " + s);

case Integer i -> System.out.println("It's an integer: " + i);

}

🧩 String Templates (Preview)

Easier and safer way to build strings with variables.

String name = "KSCodes";

System.out.println(STR."Hello, \{name}!");

🧾 Summary Table

Version	Key Features
Java 8	Lambdas, Streams, Optional, Date API
Java 9	Modules, JShell
Java 10	`var` keyword
Java 11	LTS, String utilities
Java 14	Switch Expressions
Java 15	Text Blocks
Java 16	Records
Java 17	Sealed Classes, LTS
Java 19	Virtual Threads (Preview)
Java 21	Virtual Threads, Pattern Matching, Record Patterns, String Templates

🧠 Final Thoughts

From Java 8’s lambdas to Java 21’s virtual threads, the language has become more expressive, efficient, and ready for modern application development. Isn’t the Java 8 to Java 21 evolution mind blowing?
Each version brings small improvements that add up to a powerful developer experience.

If you’re learning Java today, start with Java 21 — it’s packed with features that make learning and building easier than ever!

Next to learn is Records in Java: Simpler POJOs for Modern Java