Java SE 23 language features and code examples

Java SE 23, released in September 2023, brings a range of enhancements and language updates designed to improve performance, security, and ease of use. This release includes new preview features, API enhancements, garbage collection improvements, and more. Let’s dive into the main changes introduced in Java SE 23 and what they mean for developers.

1. New Preview Features in Java SE 23

Java SE 23 includes several new preview features that developers can test and provide feedback on before they are finalized. Notable preview features include:

Sequenced Collections (Second Preview)

The SequencedCollection interface, which unifies List, Set, and Deque collections, returns for a second preview. This feature adds methods like getFirst() and getLast(), enabling ordered iteration and reverse traversal.

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Unnamed Patterns and Variables (Second Preview)

Unnamed patterns and variables simplify code readability by allowing developers to omit naming variables in complex structures. This feature is especially useful for pattern matching in records and switch expressions.

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Pattern Matching for Switch (Fifth Preview)

Pattern matching for switch statements is further refined in Java SE 23, enhancing readability and making code more expressive, particularly when working with records.

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2. Library and API Enhancements

Java SE 23 introduces updates to the Java Standard Library, improving performance and adding useful functionalities:

HttpClient API Improvements

The HttpClient API now handles HTTP/2 and HTTP/3 protocols more efficiently, optimizing network performance and reducing latency.

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Foreign Function & Memory API (Third Preview)

With further improvements, this API allows Java applications to interact with native memory more safely and efficiently. Enhanced MemorySession and native interactions are perfect for high-performance applications.

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Enhanced Virtual Threads (Project Loom)

Virtual threads receive additional improvements, offering better scalability for concurrent applications. These lightweight threads are ideal for applications handling many simultaneous connections.

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3. Platform Changes and JVM Enhancements

Java SE 23 focuses on JVM optimizations that boost start-up times, garbage collection, and overall performance.

Garbage Collection Enhancements

Improvements across G1, ZGC, and Shenandoah garbage collectors help reduce latency and enhance memory management. These updates support high-load, real-time applications with optimized pause times.

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Improved Start-Up Time

Java SE 23 enhances start-up and warm-up times, which is particularly beneficial for containerized and cloud-native applications that frequently restart.

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4. Deprecations and Removals

As Java evolves, certain older features are deprecated or removed to streamline the platform and maintain security standards.

Deprecated and Removed Features

Java SE 23 removes some previously deprecated elements and marks others as deprecated, signaling a shift towards more modern, secure alternatives. Developers should prepare for these changes in future releases.

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5. Language and Syntax Refinements

Java SE 23 refines syntax and improves null handling constructs, allowing developers to write more concise, null-safe code.

Simplified Null Handling

Simplified syntax for null handling makes it easier to write safe and clear code. Although a minor change, these adjustments improve code quality and readability.

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6. Enhanced Documentation and Security

Java SE 23 also brings improvements to Javadoc customization, supporting better structured documentation for developers. Security updates enhance cryptographic capabilities to keep Java secure against evolving threats.

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1. Sequenced Collections (Second Preview)

The SequencedCollection interface in Java SE 23 unifies List, Set, and Deque, adding ordered access methods like getFirst(), getLast(), and reversed() iteration. This makes it easier to handle collections in a predictable order.

Example:

import java.util.*;

public class SequencedCollectionExample {
    public static void main(String[] args) {
        SequencedCollection<String> sequencedList = new ArrayList<>(List.of("Java", "Python", "Kotlin"));
        
        System.out.println("First Element: " + sequencedList.getFirst());  // Outputs: Java
        System.out.println("Last Element: " + sequencedList.getLast());    // Outputs: Kotlin

        // Add elements to the beginning and end
        sequencedList.addFirst("C++");
        sequencedList.addLast("Swift");

        System.out.println("Updated Collection: " + sequencedList);

        // Reverse iteration
        for (String language : sequencedList.reversed()) {
            System.out.print(language + " ");
        }
        // Outputs: Swift Kotlin Python Java C++
    }
}

Note: SequencedCollection is a preview feature, so you'll need to enable it in preview mode when running this code in Java SE 23.

2. Pattern Matching for Switch (Fifth Preview)

Pattern Matching in switch expressions has been enhanced in Java SE 23, making it more concise when dealing with complex data types. Here’s an example where switch is used to handle different object types:

Example:

public class PatternMatchingSwitchExample {
    public static void main(String[] args) {
        Object obj = 10;

        String result = switch (obj) {
            case Integer i -> "Integer with value: " + i;
            case String s when s.length() > 5 -> "Long string: " + s;
            case String s -> "String with value: " + s;
            case null -> "It's null!";
            default -> "Unknown type!";
        };

        System.out.println(result);  // Outputs: Integer with value: 10
    }
}

In this example:

• switch matches the type of obj and executes different code blocks depending on the object's type.
• The syntax is simplified, making the code cleaner and easier to read.

3. Unnamed Patterns and Variables (Second Preview)

Java SE 23 introduces unnamed patterns and variables, allowing you to omit variable names for unused data in pattern matching. This feature can improve readability in complex pattern structures.

Example:

public class UnnamedPatternsExample {
    public static void main(String[] args) {
        record Person(String name, int age) {}

        Object obj = new Person("Alice", 30);

        if (obj instanceof Person(_, int age)) {
            System.out.println("Age: " + age);  // Outputs: Age: 30
        }
    }
}

In this example:

• The underscore _ in Person(_, int age) represents an unnamed pattern, allowing us to ignore the name field while still capturing the age field.
• Unnamed patterns reduce verbosity, especially in nested patterns.

Conclusion

Java SE 23’s new language features make Java more expressive and concise, improving both the readability and functionality of Java code. From ordered Sequenced Collections to refined Pattern Matching and the flexibility of Unnamed Patterns, these updates are a significant step forward. Try them out in preview mode and see how they can enhance your development experience!

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