Java has evolved tremendously since the landmark release of Java 8 in March 2014. For those applying for Java positions, junior developers starting their careers, or students learning programming fundamentals, understanding Java’s evolution is crucial. This blog explores the journey of Java through its major releases, highlighting key features that have transformed the language into what it is today.

Java 8 (March 2014) – The Revolution Begins

Java 8 marked one of the most significant updates in Java’s history, introducing functional programming concepts to the language.

Key Features:

1. Lambda Expressions: Perhaps the most revolutionary addition, lambdas brought functional programming to Java. They provide a clear and concise way to represent one method interface using an expression.

// Pre-Java 8
Collections.sort(names, new Comparator<String>() {
    @Override
    public int compare(String a, String b) {
        return a.compareTo(b);
    }
});

// With Java 8 lambdas
Collections.sort(names, (a, b) -> a.compareTo(b));

2. Stream API: This allows developers to process collections of objects in a declarative way, supporting functional-style operations on streams of elements.

List<String> filteredNames = names.stream()
    .filter(name -> name.startsWith("J"))
    .collect(Collectors.toList());

3. Default Methods: Enabled interface evolution by allowing interfaces to have methods with implementation.

interface Vehicle {
    default void print() {
        System.out.println("I am a vehicle!");
    }
}

4. Method References: Provided a way to refer to methods without executing them, using syntax like ClassName::methodName.

names.forEach(System.out::println);

5. Optional Class: Introduced to avoid null pointer exceptions by wrapping potentially null values.

Optional<String> optional = Optional.of("value");
optional.ifPresent(System.out::println);

6. New Date and Time API: Replaced the notoriously problematic older date and time classes with a comprehensive, immutable, and thread-safe API.

LocalDate today = LocalDate.now();
LocalDateTime dateTime = LocalDateTime.of(2023, Month.APRIL, 1, 10, 30);

Java 8 remains a foundational release that still powers countless applications today. Its long-term support ended in March 2022, though extended support continues for enterprise users.

Java 9 (September 2017) – Modular Revolution

After a long gap, Java 9 brought significant architectural changes with the modular system, fundamentally changing how Java applications are organized.

Key Features:

1. Java Platform Module System (JPMS): Introduced the concept of modules, allowing developers to create modular JAR files that explicitly declare dependencies.

// module-info.java
module com.example.myapp {
    requires java.sql;
    exports com.example.myapp.api;
}

2. JShell: Added an interactive REPL (Read-Evaluate-Print Loop) tool for quickly testing Java code snippets.
3. Factory Methods for Collections: Simplified the creation of immutable collections.

List<String> list = List.of("one", "two", "three");
Map<String, Integer> map = Map.of("one", 1, "two", 2);

4. Stream API Enhancements: Added methods like takeWhile, dropWhile, and ofNullable.

Stream.iterate(1, i -> i < 10, i -> i + 1)
      .forEach(System.out::println);

5. Private Interface Methods: Extended interfaces to allow private methods.
6. HTTP/2 Client: Introduced a new HTTP client supporting HTTP/2 (incubator module).

Java 10 (March 2018) – Local Variable Type Inference

Java 10 marked the beginning of the six-month release cycle, with fewer but more frequent updates.

Key Features:

1. Local Variable Type Inference: Introduced the var keyword for local variable declarations.

// Instead of
ArrayList<String> names = new ArrayList<>();

// You can write
var names = new ArrayList<String>();

2. Garbage Collection Improvements: Application Class-Data Sharing and parallel full GC for G1.
3. Time-Based Release Versioning: Established the new six-month release cadence.

Java 11 (September 2018) – Long-Term Support

Java 11 was the first long-term support (LTS) release after Java 8, making it a significant milestone for enterprise adoption.

Key Features:

1. HTTP Client: Standardized the HTTP client from Java 9’s incubator module.

HttpClient client = HttpClient.newHttpClient();
HttpRequest request = HttpRequest.newBuilder()
      .uri(URI.create("https://openjdk.org/"))
      .build();
client.sendAsync(request, HttpResponse.BodyHandlers.ofString())
      .thenApply(HttpResponse::body)
      .thenAccept(System.out::println);

2. New String Methods: Added useful methods like isBlank(), strip(), stripLeading(), stripTrailing(), and lines().

String multiline = "Line 1\nLine 2\nLine 3";
multiline.lines().forEach(System.out::println);

3. Running Java Files Directly: Allowed running single-file Java programs without explicit compilation.

java HelloWorld.java

4. Flight Recorder: Made JDK Flight Recorder (JFR) open source for performance analysis.
5. Deprecation of Java EE and CORBA Modules: Began the removal of older enterprise modules from the core JDK.

Java 12 (March 2019) – Switch Expressions Preview

Java 12 introduced preview features, allowing developers to test upcoming language features before finalization.

Key Features:

1. Switch Expressions (Preview): Enhanced the switch statement to also work as an expression.

// Preview feature in Java 12
String result = switch (day) {
    case "MONDAY", "FRIDAY" -> "Start or end of work week";
    case "TUESDAY", "WEDNESDAY", "THURSDAY" -> "Mid-week";
    case "SATURDAY", "SUNDAY" -> "Weekend";
    default -> "Invalid day";
};

2. Compact Number Formatting: Simplified number formatting for more readable output.

NumberFormat fmt = NumberFormat.getCompactNumberInstance(Locale.US, NumberFormat.Style.SHORT);
String result = fmt.format(1000); // "1K"

3. Microbenchmark Suite: Added JMH-based microbenchmarks to the JDK source code.

Java 13 (September 2019) – Text Blocks Preview

Java 13 continued refining the language with preview features focusing on developer productivity.

Key Features:

1. Text Blocks (Preview): Introduced multi-line string literals for improved readability.

// Preview feature in Java 13
String html = """
              <html>
                  <body>
                      <p>Hello, World!</p>
                  </body>
              </html>
              """;

2. Switch Expressions Enhancements: Refined the switch expressions from Java 12.
3. ZGC Improvements: Enhanced the Z Garbage Collector with significant performance improvements.

Java 14 (March 2020) – Pattern Matching Preview

Java 14 brought more preview features, continuing to evolve the language toward more expressive and concise code.

Key Features:

1. Pattern Matching for instanceof (Preview): Simplified type checks and casting.

// Preview feature in Java 14
if (obj instanceof String s) {
    // Can use s directly here without casting
    System.out.println(s.length());
}

2. Records (Preview): Introduced a new type declaration for data carrier classes.

// Preview feature in Java 14
record Point(int x, int y) {}

3. Switch Expressions (Standard): Finalized the switch expressions from previous previews.
4. Helpful NullPointerExceptions: Improved error messages for null pointer exceptions, specifying which variable was null.
5. JFR Event Streaming: Added an API for continuous consumption of JDK Flight Recorder data.

Java 15 (September 2020) – Sealed Classes Preview

Java 15 introduced several preview features focused on type safety and pattern matching.

Key Features:

1. Sealed Classes (Preview): Restricted which other classes or interfaces can extend or implement them.

// Preview feature in Java 15
sealed interface Shape permits Circle, Rectangle, Square {}

2. Text Blocks (Standard): Finalized the text blocks feature from previous previews.
3. Records (Second Preview): Continued development of the records feature.
4. Pattern Matching for instanceof (Second Preview): Refined the pattern matching feature.
5. Hidden Classes: Added support for classes that cannot be used directly by other classes.
6. Foreign-Memory Access API (Incubator): Introduced an API for accessing memory outside of the Java heap.

Java 16 (March 2021) – Record Classes

Java 16 had a remarkable 17 JEPs (JDK Enhancement Proposals), focusing on developer productivity and platform enhancements.

Key Features:

1. Records (Standard): Finalized records as a standard feature.

record Customer(long id, String name, String email) {}

2. Pattern Matching for instanceof (Standard): Finalized pattern matching for instanceof.
3. Unix-Domain Socket Channels: Added support for Unix-domain socket communication.
4. Vector API (Incubator): Introduced an API for expressing vector computations.
5. ZGC Concurrent Thread-Stack Processing: Improved ZGC performance by making thread-stack processing concurrent.
6. Foreign Linker API (Incubator): Introduced an API for Java code to interoperate with code and data outside of the JVM.

Java 17 (September 2021) – Long-Term Support

Java 17 was another LTS release, incorporating many improvements from the previous six-month releases.

Key Features:

1. Sealed Classes (Standard): Finalized sealed classes from previous previews.

sealed interface Vehicle permits Car, Truck, Motorcycle {}

final class Car implements Vehicle {}
final class Truck implements Vehicle {}
non-sealed class Motorcycle implements Vehicle {}

2. Pattern Matching for switch (Preview): Extended pattern matching to switch expressions and statements.

// Preview feature in Java 17
String result = switch (obj) {
    case Integer i -> "Integer: " + i;
    case String s -> "String: " + s;
    case null -> "null";
    default -> "Unknown";
};

3. Strong Encapsulation of JDK Internals: Effectively sealed internal APIs against illegal access.
4. Foreign Function & Memory API (Incubator): Merged the Foreign-Memory Access API and the Foreign Linker API.
5. Deprecating the Security Manager: Began the process of removing the security manager.

Java 18 (March 2022) – UTF-8 by Default

Java 18 continued the six-month release cadence with incremental improvements.

Key Features:

1. UTF-8 by Default: Made UTF-8 the default charset for standard Java APIs.
2. Simple Web Server: Added a minimal HTTP server for prototyping and testing.

jwebserver -p 8000

3. Pattern Matching for switch (Second Preview): Enhanced the pattern matching for switch.
4. Code Snippets in Java API Documentation: Improved the Javadoc tool to better support code snippets.
5. Foreign Function & Memory API (Second Incubator): Continued refinement of the API.

Java 19 (September 2022) – Virtual Threads Preview

Java 19 introduced several preview features focusing on concurrency and developer experience.

Key Features:

1. Virtual Threads (Preview): Introduced lightweight threads for high-throughput concurrent applications.

// Preview feature in Java 19
try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
    IntStream.range(0, 10_000).forEach(i -> {
        executor.submit(() -> {
            Thread.sleep(Duration.ofSeconds(1));
            return i;
        });
    });
}

2. Structured Concurrency (Incubator): Simplified multithreaded programming.
3. Pattern Matching for switch (Third Preview): Further refined pattern matching for switch.
4. Record Patterns (Preview): Extended pattern matching to deconstruct record values.

// Preview feature in Java 19
if (obj instanceof Point(int x, int y)) {
    System.out.println(x + ", " + y);
}

5. Foreign Function & Memory API (Preview): Promoted from incubator status.

Java 20 (March 2023) – Scoped Values Incubator

Java 20 continued refining features from previous releases.

Key Features:

1. Record Patterns (Second Preview): Enhanced pattern matching for records.
2. Pattern Matching for switch (Fourth Preview): Further refined pattern matching for switch.
3. Scoped Values (Incubator): Introduced an alternative to ThreadLocal for sharing immutable data.

// Incubator feature in Java 20
final ScopedValue<User> CURRENT_USER = ScopedValue.newInstance();

void process() {
    ScopedValue.where(CURRENT_USER, new User("admin"))
        .run(() -> service.doWork());
}

4. Virtual Threads (Second Preview): Continued refinement of virtual threads.
5. Structured Concurrency (Second Incubator): Further development of structured concurrency.

Java 21 (September 2023) – Long-Term Support

Java 21 was the latest LTS release, finalizing many preview features and introducing new capabilities.

Key Features:

1. Virtual Threads (Standard): Finalized virtual threads for high-throughput concurrent applications.

Thread thread = Thread.startVirtualThread(() -> {
    System.out.println("Running in a virtual thread");
});

2. Pattern Matching for switch (Standard): Finalized pattern matching for switch statements.

String result = switch (obj) {
    case Integer i when i > 0 -> "Positive integer: " + i;
    case Integer i -> "Other integer: " + i;
    case String s -> "String: " + s;
    case null -> "null";
    default -> "Unknown";
};

3. Record Patterns (Standard): Finalized record patterns for deconstructing record values.
4. Sequenced Collections: Added interfaces that describe collections with a well-defined encounter order.

List<String> list = List.of("one", "two", "three");
String first = list.getFirst();
String last = list.getLast();

5. Unnamed Patterns and Variables (Preview): Introduced the underscore _ as a way to discard pattern variables.

// Preview feature in Java 21
if (obj instanceof Point(_, int y)) {
    // We don't care about the x coordinate
    System.out.println("Y coordinate: " + y);
}

6. String Templates (Preview): Added template expressions for string interpolation.

// Preview feature in Java 21
String name = "World";
String message = STR."Hello, \{name}!";

7. Structured Concurrency (Standard): Simplified multithreaded programming by treating groups of related tasks as a single unit of work.

Java 22 (March 2024) – Unnamed Classes and Instance Main Methods

Java 22 continued evolving the language with more developer-friendly features.

Key Features:

1. Foreign Function & Memory API (Standard): Finalized the API for interoperating with code and data outside the JVM.
2. Unnamed Classes and Instance Main Methods (Preview): Simplifying the entry point for Java applications.

// Preview feature in Java 22
void main() {
    System.out.println("Hello, World!");
}

3. String Templates (Second Preview): Enhanced string interpolation capabilities.

// Preview feature in Java 22
String name = "user";
String html = STR."""
              <html>
                  <body>
                      <h1>Hello, \{name}!</h1>
                  </body>
              </html>
              """;

4. Unnamed Variables and Patterns (Standard): Finalized the underscore pattern variable.
5. Vector API (Sixth Incubator): Continued development of the API for vector computations.
6. Scoped Values (Second Preview): Further refinement of the alternative to ThreadLocal.

Java 23 (September 2024) – Enhanced Pattern Matching

Java 23 is the most recent release, bringing further refinements to pattern matching and other features.

Key Features:

1. Unnamed Classes and Instance Main Methods (Standard): Simplified Java application entry points.
2. String Templates (Standard): Finalized string interpolation features.
3. Scoped Values (Standard): Finalized the API for sharing immutable data.
4. Enhanced Pattern Matching (Preview): Extended pattern matching with more powerful type patterns.

// Preview feature in Java 23
if (obj instanceof List<Integer> list) {
    // Direct access to the typed list
}

5. Implicitly Declared Classes (Preview): Further simplified class declarations for simple use cases.

// Preview feature in Java 23
class {
    void main() {
        System.out.println("Hello, simplified world!");
    }
}

6. Vector API (Seventh Incubator): Continued development of the vector computation API.

The Impact on Java Development

The evolution of Java since version 8 has significantly transformed how developers write code:

1. More Concise Syntax

Modern Java code is much more concise than pre-Java 8 code. Features like lambda expressions, stream API, var for local variables, and records have greatly reduced boilerplate code.

2. Functional Programming Paradigm

Java has embraced functional programming concepts, allowing developers to write more declarative and less imperative code.

3. Improved Performance

Innovations like the Z Garbage Collector, virtual threads, and the Vector API have substantially improved Java’s performance, especially for concurrent applications.

4. Better Developer Experience

Features like JShell, helpful NullPointerExceptions, and text blocks have enhanced the developer experience, making Java more approachable for beginners.

5. Modular Architecture

The module system has improved application security, performance, and maintainability through strong encapsulation and explicit dependencies.

Staying Current with Java

For job seekers, junior developers, and students, staying current with Java is essential. Here are some strategies:

1. Focus on LTS Versions First

If you’re just starting, focus on learning the features of LTS releases (Java 8, 11, 17, 21) before diving into the interim releases.

2. Practice with New Features

Create small projects that use newer Java features to gain hands-on experience.

3. Learn Related Ecosystems

Familiarize yourself with common frameworks and libraries like Spring Boot, Hibernate, and JUnit that leverage modern Java features.

4. Follow Release Notes

Keep an eye on the OpenJDK project’s release notes and JEPs to stay informed about upcoming features.

5. Participate in the Community

Join Java user groups, follow Java champions on social media, and participate in forums to keep up with best practices.

Conclusion

The evolution of Java from version 8 to the present demonstrates Oracle’s commitment to keeping the language modern, performant, and developer-friendly. With each release, Java has become more expressive and powerful, while maintaining its core strengths of readability, stability, and backward compatibility.

For those aspiring to work with Java professionally, understanding this evolution is vital. The language continues to adapt to modern computing challenges while preserving its “write once, run anywhere” philosophy that has made it a staple in enterprise development for nearly three decades.

Whether you’re preparing for a job interview, starting your development career, or learning Java as a student, embracing the language’s newer features will make you more effective and marketable in an ever-evolving technological landscape.

Remember that Java’s release cadence now includes a new version every six months, with long-term support versions every two years. This strategy balances innovation with stability, allowing developers to choose between staying on the cutting edge or prioritizing long-term maintenance.

As you continue your Java journey, focus not just on the syntax changes but also on understanding the design principles and patterns that these new features enable. This deeper knowledge will help you write more elegant, efficient, and maintainable code—skills that are invaluable in any Java development role.