Java 8 to Java 17: New Features and Hassle-Free Migration

Java, the widely-used programming language, as it continues to evolve with each new release I still see companies and projects hesitating to transition from Java 8 to Java 17, the latest long-term support (LTS) release. This leads them into either using unsupported Java 8 versions or paying a heavy fee for support or for the usage of an alternative VM like Azul. The transition from Java 8 to Java 17 has brought about numerous enhancements and features that developers can leverage to create more efficient and robust applications. In this article, we will delve into the new features introduced in Java 17, compare them with Java 8, and provide best practices for migrating from Java 8 to Java 17.

1. Overview

Java 17, the latest long-term support (LTS) release, offers several improvements over Java 8. These enhancements range from language features to performance optimizations and JVM changes. To help you understand the differences between these two versions and make an informed decision about migration, we will discuss the most significant changes and their implications for Java software development.

2. Language Features

2.1. Sealed Classes

One notable addition in Java 17 is sealed classes. Sealed classes allow developers to define a restricted set of subclasses for a given class or interface. This feature enhances the expressiveness of domain models and simplifies the implementation of domain-driven design.

public sealed class Shape permits Circle, Square, Triangle {
}

2.2. Records

Records in Java 17 are a concise way to define immutable data objects. They automatically generate boilerplate code such as constructors, getters, equals(), hashCode(), and toString() methods.

public record Student(int rollNo, String name) {
}

2.3. Pattern Matching

Java 17 introduces pattern matching features aimed at simplifying conditional extraction of components from objects.

2.3.1. Enhanced instanceof Operator

The enhanced instanceof operator allows developers to create a local variable inside an if statement, simplifying type checking and casting.

if (obj instanceof MyObject myObject) {
    // … further logic
}

2.3.2. Switch Expressions

Switch expressions in Java 17 provide a more concise and flexible way to handle multiple cases, eliminating the need for explicit break statements.

double circumference = switch(shape) {
    case Rectangle r -> 2 * r.length() + 2 * r.width();
    case Circle c -> 2 * c.radius() * Math.PI;
    default -> throw new IllegalArgumentException("Unknown shape");
};

2.4. Text Blocks

Java 17 introduces text blocks, a more readable and concise way to represent multiline strings.

String textBlock = """
    Line 1
    Line 2
    Line 3
    """;

2.5. New String Methods

Java 17 adds several convenient methods to the String class, such as isBlank(), repeat(), indent(), lines(), strip(), and transform().

assertThat("  ".isBlank());
assertThat("Twinkle ".repeat(2)).isEqualTo("Twinkle Twinkle ");
assertThat("Format Line".indent(4)).isEqualTo("    Format Line\n");
assertThat("Line 1 \n Line2".lines()).asList().size().isEqualTo(2);
assertThat(" Text with white spaces   ".strip()).isEqualTo("Text with white spaces");

3. JVM Enhancements

3.1. Project Jigsaw

Project Jigsaw in Java 9 introduced modularity to the Java platform, making it more scalable and maintainable. This project significantly impacted the internal workings of the JVM, but most developers can seamlessly adopt the new features without diving deep into the changes.

3.2. Garbage Collectors

Java 17 offers several garbage collectors, such as G1, ZGC, and Shenandoah, that improve application performance by reducing pause times and memory overhead.

3.3. Container Awareness

Java 17 is container-aware, meaning it can correctly recognize and adhere to memory limits set by containers. This feature helps avoid issues related to memory allocation and improves application performance in containerized environments.

3.4. Class Data Sharing (CDS) Archives

CDS Archives in Java 17 enable faster application startup times by allowing the JVM to share class metadata between different Java processes.

4. Migration Best Practices

4.1. Assess the Current State of Your Java 8 Application

Before migrating to Java 17, it’s essential to evaluate your Java 8 application thoroughly. Identify the libraries and frameworks used, along with any custom classloaders, Unsafe usages, or sun.misc or sun.security dependencies. This assessment will help you understand the scope and complexity of the migration process.

4.2. Update Libraries and Frameworks

Ensure that all the libraries and frameworks used in your application are compatible with Java 17. Update them to the latest versions, if necessary, to guarantee a smooth migration.

4.3. Use Migration Tools and Guides

Leverage Java migration tools like the Java Dependency Analysis Tool (JDEP) to identify potential issues during the migration process. Also, consult migration guides and release notes from popular frameworks, like Spring Boot, to address any compatibility concerns.

4.4. Test, Test, Test

Thoroughly test your application after migrating to Java 17. Be sure to run unit tests, integration tests, and performance tests to validate the correctness and performance of the migrated application.

5. Conclusion

Migrating from Java 8 to Java 17 can bring numerous benefits, including improved language features, performance enhancements, and long-term support. While the migration process may require some effort, the advantages of using Java 17 make it a worthwhile investment. By following best practices and thoroughly assessing your application, you can ensure a hassle-free migration from Java 8 to Java 17.