Cleaner

Cleaner 是 Java 9 引入的資源清理機制，用于在對象被垃圾回收后自動或手動執行清理操作，替代 finalize()，安全、異步且高效。

public final class Cleaner {final CleanerImpl impl;static {CleanerImpl.setCleanerImplAccess(new Function<Cleaner, CleanerImpl>() {@Overridepublic CleanerImpl apply(Cleaner cleaner) {return cleaner.impl;}});}private Cleaner() {impl = new CleanerImpl();}// 創建一個新的 Cleaner，使用默認后臺守護線程處理清理任務。public static Cleaner create() {Cleaner cleaner = new Cleaner();cleaner.impl.start(cleaner, null);return cleaner;}// 使用指定線程工廠創建 Cleaner，適合自定義線程配置（如優先級、命名）。public static Cleaner create(ThreadFactory threadFactory) {Objects.requireNonNull(threadFactory, "threadFactory");Cleaner cleaner = new Cleaner();cleaner.impl.start(cleaner, threadFactory);return cleaner;}// 注冊一個對象與清理任務，當對象被 GC 回收后，后臺線程執行 action。返回 Cleanable 可用于提前清理。public Cleanable register(Object obj, Runnable action) {Objects.requireNonNull(obj, "obj");Objects.requireNonNull(action, "action");return new CleanerImpl.PhantomCleanableRef(obj, this, action);}// 表示一次清理任務，調用 clean() 方法可以手動執行清理邏輯，只會執行一次。public interface Cleanable {void clean();}}