Unlock Java 21: New Features, Virtual Threads, and Migration Tips

1. Introduction

Java 21 was officially released on September 20, 2023 as the next LTS version after Java 17. Virtual threads become a standard feature, and Spring Boot 3.2 can enable them by setting

spring.threads.virtual.enabled=true

. Java 21 is expected to become as popular as Java 8.

2. Java 21 Feature Updates

2.1 Official Features

Virtual Threads

Sequenced Collections

Record Patterns

Pattern Matching for switch

Generational ZGC

Deprecate the Windows 32‑bit x86 Port for Removal

Prepare to Disallow the Dynamic Loading of Agents

Key Encapsulation Mechanism API

3. Switching Development Environment to Java 21

The author uses the Azul Zulu distribution.

IntelliJ IDEA 2023.2.2 is required to configure the Java 21 environment.

4. Lombok Incompatibility with Java 21

When compiling the PIGX project, the following error occurs:

<code>An annotation processor threw an uncaught exception.
Consult the following stack trace for details.
java.lang.NoSuchFieldError: Class com.sun.tools.javac.tree.JCTree$JCImport does not have member field 'com.sun.tools.javac.tree.JCTree qualid'
    at lombok.javac.JavacImportList.getFullyQualifiedNameForSimpleNameNoAliasing(JavacImportList.java:53)
    at lombok.core.TypeResolver.typeRefToFullyQualifiedName(TypeResolver.java:60)
    at lombok.javac.HandlerLibrary.handleAnnotation(HandlerLibrary.java:247)
    at lombok.javac.JavacTransformer$AnnotationVisitor.visitAnnotationOnType(JavacTransformer.java:79)
    at lombok.javac.JavacNode.traverse(JavacNode.java:132)
    at lombok.javac.JavacAST.traverseChildren(JavacAST.java:222)
</code>

Updating Lombok to the latest version 1.18.30 resolves the issue. Because PIGX uses a unified BOM for dependency management, the version can be updated globally in the common‑bom.