What are the main features of Java 17?

Table of Contents

• Introduction
• Key Features of Java 17
  • 1. Sealed Classes
    • Example:
  • 2. Pattern Matching for **instanceof**
    • Example:
  • 3. Enhanced **switch** Expressions
    • Example:
  • 4. Text Blocks as Standard
    • Example:
• Additional Features in Java 17
  • 1. Removal of Deprecated Features
  • 2. Foreign Function and Memory API (Incubator)
  • 3. Vector API (Second Incubator)
  • 4. Improved Garbage Collection (G1 and ZGC)
  • 5. Performance Improvements
• Practical Example: Using Sealed Classes and Enhanced switch
  • Step 1: Define a Sealed Class
  • Step 2: Use an Enhanced switch Expression
• Conclusion

Introduction

Java 17 is a long-term support (LTS) release that brings various new features, enhancements, and improvements to the language. As the LTS version, Java 17 will be supported for an extended period, making it a critical upgrade for developers building and maintaining long-lasting applications. In this guide, we’ll explore the main features introduced in Java 17 and how they enhance the language's capabilities, usability, and performance.

Key Features of Java 17

1. Sealed Classes

Sealed classes restrict which other classes or interfaces can extend or implement them. This allows developers to define clear inheritance hierarchies, ensuring more control over class hierarchies while maintaining flexibility.

Example:

With sealed classes, only Circle and Square can extend the Shape class, preventing unwanted subclasses from being added.

2. Pattern Matching for **instanceof**

Java 17 continues the enhancement of pattern matching for instanceof, introduced in earlier versions. It simplifies the casting process by allowing inline type checks and variable declarations.

Example:

In this example, you no longer need a separate cast after using instanceof, reducing boilerplate code.

3. Enhanced **switch** Expressions

Java 17 extends the capabilities of switch expressions by allowing the yield keyword to return values from the switch block. This makes switch more expressive and functional, supporting both statement and expression forms.

Example:

This enhancement improves readability and simplifies control flow when returning values.

4. Text Blocks as Standard

Text blocks were introduced earlier but are now fully supported in Java 17. Text blocks make it easier to work with multi-line strings, improving code readability.

Example:

Text blocks reduce the need for excessive escaping and make long strings more manageable.

Additional Features in Java 17

1. Removal of Deprecated Features

Java 17 continues the trend of cleaning up legacy components by removing several deprecated features, such as the applet API and RMI Activation.

2. Foreign Function and Memory API (Incubator)

This new API provides an easier way to interact with native code and memory outside the JVM, offering improved performance and memory management capabilities. Although still in an incubator phase, it shows Java's commitment to better integration with native code.

3. Vector API (Second Incubator)

The Vector API helps developers write vectorized operations that can be optimized by modern CPU architectures. This API is designed to improve performance for computations involving large data sets, such as scientific applications or machine learning.

4. Improved Garbage Collection (G1 and ZGC)

Java 17 introduces optimizations for garbage collectors, particularly G1 and ZGC. These enhancements reduce pause times and improve memory efficiency, resulting in better overall performance for applications running on the JVM.

5. Performance Improvements

With every release, the JVM continues to see performance upgrades. Java 17 improves startup times, memory usage, and runtime performance through ongoing optimizations in the JIT (Just-In-Time) compiler and garbage collection mechanisms.

Practical Example: Using Sealed Classes and Enhanced switch

Here’s a practical example showcasing how sealed classes and the enhanced switch expression can be used together in Java 17.

Step 1: Define a Sealed Class

Step 2: Use an Enhanced switch Expression

In this example, sealed classes restrict the subclasses of Vehicle, while the switch expression simplifies the process of handling different vehicle types.

Conclusion

Java 17 introduces several powerful features that simplify code, improve performance, and enhance developer productivity. The addition of sealed classes, pattern matching for instanceof, enhanced switch expressions, and memory management optimizations make Java 17 a compelling upgrade for developers. As the latest long-term support (LTS) release, Java 17 is designed to be a stable, performant, and feature-rich platform for building modern Java applications.