Java 21 is a Long-Term Support (LTS) release, officially available since September 19, 2023, and will receive free updates under Oracle’s No Fee Terms & Conditions (NFTC) license until September 16, 2026.

Key Features in Java 21

• Virtual Threads: Lightweight threads that simplify high-throughput concurrent applications, enabling the "thread-per-request" model with near-optimal hardware utilization.

• Sequenced Collections: New interfaces (SequencedCollection, SequencedMap, SequencedSet) for efficient access to first/last elements and reverse traversal.

• Pattern Matching for switch and Record Patterns: Simplifies complex data navigation with concise, safe syntax for switch expressions and record deconstruction.

• String Templates (Preview): A new language feature for safely embedding expressions in strings, improving readability and reducing errors in logs and SQL.

• Scoped Values (Preview): Enables safe, efficient sharing of data across method calls without using thread-local variables, ideal for virtual threads.

• Generational ZGC: Enhances garbage collection performance by separating young and old objects for more efficient collection.

• Structured Concurrency (Preview): Provides APIs to treat groups of tasks as a single unit, improving error handling and cancellation.

Download Java 21

You can download JDK 21 from Oracle’s official site:

• Download JDK 21 (Free)

Available for:

• Windows: x64 Installer (.exe), Compressed Archive (.zip), MSI Installer

• macOS: ARM64 and x64 DMG Installers and Compressed Archives

• Linux: x64 and ARM64 DEB, RPM, and Compressed Archive formats

✅ Note: Oracle JDK 21 will be free for commercial use until September 16, 2026. After that, licensing requires a subscription. Alternatively, use free OpenJDK distributions like Azul Zulu, Eclipse Temurin, or build from OpenJDK source.

Java 21 and Minecraft

Java 21 is not required for Minecraft 1.21. The latest Minecraft versions use Java 17 or Java 21 depending on the version. For example, Minecraft 1.21 supports Java 21, but it's not mandatory. Use seeds like:

• 2422215857861955386 (Ancient City, Village)

• -767300786513247025 (Village, Woodland Mansion, Pillager Outpost)

Support & Migration

• JavaFX 21 (LTS) is supported with a minimum JDK of 17.

• For enterprise migration from Oracle JDK to OpenJDK, tools like Azul Migration Toolkit (AMT) and Azul Core offer support and compliance tracking.

Stay updated: Java 25 was released on September 16, 2025, making Java 21 the next LTS after Java 17.