JDK 25: The new features in Java 25

Java Development Kit (JDK) 25, a planned long-term support release of standard Java due in September, now has two features officially proposed for it. The first is a preview of an API for stable values, a feature that promises to speed up the startup of Java applications. The second is the removal of the previously deprecated 32-bit x86 port.

JDK 25 comes on the heels of JDK 24, a six-month-support release due to arrive March 18. As a long-term support release, JDK 25 is set to get at least five years of premier-level support from Oracle.

Stable values are objects that hold immutable data. Because stable values are treated as constants by the JVM, they enable the same performance optimizations that are enabled by declaring a field final. But compared to final fields, stable values offer greater flexibility as to the timing of their initialization. A chief goal of the proposal is improving the startup of Java applications by breaking up the monolithic initialization of application state. Other goals include enabling user code to safely enjoy constant-folding optimizations previously available only to JDK code; guaranteeing that stable values are initialized at most once, even in multi-threaded programs; and decoupling the creation of stable values from their initialization, without significant performance penalties.

Removal of the 32-bit x86 port, currently proposed to target JDK 25, involves removing both the source code and build support for this port, which was deprecated for removal in JDK 24. In explaining the motivation, the JEP states that the cost of maintaining this port outweighs the benefits. Keeping parity with new features, such as the foreign function memory API, is a major opportunity cost, according to the JEP. Deprecating and removing the port will allow OpenJDK developers to accelerate development of new features and enhancements.

Other features that could find a home in JDK 25 include the features previewed in JDK 24, such as a key derivation function API, scoped values, structured concurrency,  flexible constructor bodies, and module import declarations.