Java 25 为延迟不可变性引入了稳定值 API，并改进了应用程序启动

class OrderController {    private final StableValue<Logger> logger = StableValue.of();    Logger getLogger() {        return logger.orElseSet(() -> Logger.create(OrderController.class));    }}

// 传统方法 - 失去了优化机会class OrderController {    private Logger logger = null; // 可变字段    Logger getLogger() {        if (logger == null) {            logger = Logger.create(OrderController.class);        }        return logger;    }}

class DataService {    private final Supplier<DatabaseConnection> connection = StableValue.supplier(() -> new DatabaseConnection("jdbc:postgresql://localhost/db"));    void performQuery() {        DatabaseConnection db = connection.get(); // 数据库连接仅在首次访问时创建    }}

class ThreadPool {    private final List<WorkerThread> workers = StableValue.list(POOL_SIZE, index -> new WorkerThread(index));    WorkerThread getWorker(int index) {        return workers.get(index); // 仅在首次访问时创建工作线程    }}

class Application {    static final StableValue<OrderController> orders = StableValue.of();    static final StableValue<UserService> users = StableValue.of();    public static OrderController getOrderController() {        return orders.orElseSet(OrderController::new);    }}

javac --release 25 --enable-preview MyApplication.javajava --enable-preview MyApplication