What’s New in Java 15? 14 Game‑Changing Features You Must Know

Java Turns 25

2020 marks the 25th anniversary of Java, a language that has continuously evolved with innovations such as generics in Java 5, lambda expressions in Java 8, and the module system in Java 9, enhancing performance, stability, and security.

Java 15 Release

On September 15, Oracle announced the official release of JDK 15, the sixth version following the new six‑month release cadence, allowing developers to adapt more quickly to changes.

The accelerated cadence speeds up the delivery of production‑ready JDK versions, reducing the reliance on large, infrequent releases packed with thousands of fixes and dozens of JDK Enhancement Proposals (JEPs).

JDK Enhancement Proposals (JEP) are proposals for new features and improvements to the JDK.

Chinese Contributions

The OpenJDK community also benefits from contributions by Chinese companies. Oracle remains the primary contributor, handling roughly 79.68% of the work, followed by Red Hat. Notably, Tencent received public thanks from Oracle, with Alibaba and Huawei also making significant contributions, strengthening China’s IT capabilities.

Java 15 Highlights

Java 15 introduces fourteen major enhancements and changes, including an incubator module, three preview features, two deprecated features, and two removed features.

EdDSA Digital Signature Algorithm

A new Edwards‑Curve Digital Signature Algorithm (EdDSA) offers higher security and performance, already supported by libraries such as OpenSSL and BoringSSL.

Hidden Classes

Hidden classes enable frameworks that generate classes at runtime to limit access to those classes, reducing memory usage and allowing independent class‑loader loading.

Reimplemented DatagramSocket API

The legacy java.net.DatagramSocket and java.net.MulticastSocket APIs have been reimplemented with a simpler, more modern design, improving maintainability and stability.

ZGC Becomes Production‑Ready

Previously a preview feature (JEP 333), ZGC is now a production feature in JDK 15 via JEP 377, aiming to reduce GC pause times.

Text Blocks Become Permanent

Introduced as a preview in JEP 355 (2019), text blocks—multiline string literals that eliminate most escape sequences—are now a permanent language feature through JEP 378.

Shenandoah GC Becomes Production‑Ready

Shenandoah, introduced in JDK 12, reduces GC pause times independent of heap size and is now a product feature.

Sealed Classes (Preview)

Sealed classes and interfaces restrict which other classes or interfaces may extend or implement them, providing tighter control over inheritance.

Pattern‑Matching instanceof (Preview)

The new pattern‑matching instanceof syntax simplifies type checks and casting:

if (obj instanceof String s) {
    // s is already casted
} else {
    // handle other types
}

Previously, a separate type check and cast were required.

Records (Preview)

Records provide a compact syntax for immutable data carriers, reducing boilerplate code.

Foreign Memory Access API (Preview)

This API enables Java programs to safely and efficiently access off‑heap memory outside the Java heap.

Other Changes

Additional removals and deprecations include the Nashorn JavaScript engine and the Solaris/SPARC ports, along with other deprecated features.