Enhancing Initialization Flexibility: The Benefits of Computed Constants
The OpenJDK proposal aims to introduce computed constants to Java, providing immutable value holders initialized at most once. These constants promise the performance and safety benefits of final fields while offering greater flexibility in initialization timing.
Currently in draft status and targeted for standard Java adoption, the proposal underscores the importance of preferring immutability in software development. Immutable objects maintain a single state set by their constructor, which enhances control and security. They can also be safely shared across different parts of an application or with untrusted code, facilitating robustness and security. Furthermore, immutability supports various runtime optimizations, contributing to overall application efficiency.
While Java traditionally relies on final fields for immutability, these fields come with limitations, particularly in terms of initialization flexibility. Developers often face trade-offs between the strictness of final fields and the need for dynamic initialization timing. Existing strategies to mitigate these challenges have their drawbacks, prompting the need for a more comprehensive solution.
The computed constants API proposed by OpenJDK introduces new classes and interfaces within the java.lang package of the java.base module. This API empowers developers in applications and libraries to define and utilize computed constant objects and collections efficiently. By bridging the gap between final fields and flexible initialization, the computed constants API aims to streamline development practices and enhance code maintainability in Java.
The proposal is currently in a draft status and eyed for standard Java. Driving the effort is the notion that developers should “prefer immutability,” because immutability confers a number of advantages. Immutable objects can only be in one state, which is carefully controlled by its constructor. Immutable objects can be freely shared with untrusted code. And immutability enables all manner of runtime optimizations.
Java’s main tool for managing immutability is final fields, but final fields have restrictions. As a result, developers must choose between the benefits of finality and flexibility in timing of initialization. Developers have devised strategies to ameliorate the imbalance, but none are ideal.
The computed constants API defines classes and an interface so client code in applications and libraries can perform tasks including defining and using computed constant objects and constant collections. The API resides in the java.lang package of the java.base module.