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Java 14 to Java 18 New Features.md

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Java 14 to Java 18 New Features.md

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Java 14 to Java 18 New Features

This document provides a detailed explanation of all major features introduced in Java 14 to Java 18, with examples, reasoning for introduction, and previous approaches or limitations.

Java 14 (March 2020)

1. Records (Preview)

Issue: Previously, creating simple immutable data classes required verbose boilerplate code.

Introduction: Records provide a concise way to declare immutable data carriers.

Example:

record Point(int x, int y) {}
Point p = new Point(5, 10);
System.out.println(p.x()); // 5

Automatically provides equals, hashCode, and toString.

2. Pattern Matching for instanceof (Preview)

Issue: Type casting after instanceof was repetitive.

Example:

Object obj = "Hello";
if(obj instanceof String s) {
    System.out.println(s.toUpperCase());
}

Simplifies type checks and casts.

3. Helpful NullPointerExceptions

Reason: NullPointerExceptions were hard to debug.

Example:

String s = null;
s.length(); // JVM shows exactly which variable was null

4. Switch Expressions (Standardized)

Example:

int day = 2;
String type = switch(day) {
    case 1, 7 -> "Weekend";
    default -> "Weekday";
};

5. Foreign-Memory Access API (Incubator)

Reason: Efficient memory access outside the Java heap.

Example:

// Use MemorySegment, MemoryAddress to access off-heap memory

6. JFR Event Streaming

Real-time monitoring of JVM events.

Java 15 (September 2020)

1. Text Blocks (Standard)

Simplifies multi-line string literals.

String html = """
<html>
  <body>Hello</body>
</html>
""";

2. Sealed Classes (Preview)

Issue: Previously, restricting subclassing required documentation and runtime checks.

Example:

sealed interface Shape permits Circle, Rectangle {}
final class Circle implements Shape {}
non-sealed class Rectangle implements Shape {}

Restricts which classes can extend or implement a type.

3. Hidden Classes

Allows frameworks to define classes dynamically without polluting the public API.

4. Records (Second Preview)

Enhancements and fixes to record features.

5. Foreign-Memory Access API (Second Incubator)

Further improvements for off-heap memory access.

6. ZGC Improvements

Reduces pause times and improves memory management.

Java 16 (March 2021)

1. Records (Standard)

Records are now a standard feature.

record Employee(String name, int id) {}

2. Pattern Matching for instanceof (Standard)

No longer preview; simplifies type checks.

3. Stream.toList()

Example:

List<Integer> list = Stream.of(1,2,3).toList();

Simpler conversion from stream to list.

4. Sealed Classes (Second Preview)

Continued development of sealed classes.

5. Vector API (Incubator)

Reason: Efficient SIMD operations for performance-critical code.

6. Foreign Linker API (Incubator)

Simplifies calling native libraries.

7. Strong Encapsulation of JDK Internals

Encourages proper API usage, reduces internal dependency hacks.

Java 17 (September 2021, LTS)

1. Sealed Classes (Standard)

Final standardization of sealed classes.

2. Pattern Matching for switch (Preview)

Example:

Object obj = "Hello";
switch(obj) {
    case String s -> System.out.println(s.length());
    default -> System.out.println("Unknown");
}

3. New Pseudo-Random Number Generators (PRNG)

Example:

RandomGenerator rnd = RandomGenerator.of("L64X128MixRandom");
int num = rnd.nextInt(100);

4. jpackage Tool

Create native installers for Java applications.

5. Foreign Function & Memory API (Incubator)

Enhances JVM support for off-heap memory and native calls.

6. Deprecations & Removals

Applets, RMI Activation, and older APIs removed.

Java 18 (March 2022)

1. Simple Web Server

Reason: Quickly run small HTTP servers for testing.

Example:

java -m jdk.httpserver 8000

2. UTF-8 by Default

All charset operations default to UTF-8, simplifying internationalization.

3. Vector API (Second Incubator)

Enhancements to SIMD operations for high-performance code.

4. Code Snippets in API Documentation

Allows adding executable code snippets to Javadoc.

5. Pattern Matching for switch (Second Preview)

Continued improvements on switch pattern matching.

6. Foreign Function & Memory API (Second Incubator)

Further refinements for off-heap memory and native function access.