[java: Cleaner]-一文述之

Cleaner

Cleaner 是 Java 9 引入的资源清理机制，用于在对象被垃圾回收后自动或手动执行清理操作，替代 finalize()，安全、异步且高效。

public final class Cleaner {

    final CleanerImpl impl;

    static {
        CleanerImpl.setCleanerImplAccess(new Function<Cleaner, CleanerImpl>() {
            @Override
            public CleanerImpl apply(Cleaner cleaner) {
                return cleaner.impl;
            }
        });
    }
    
    private Cleaner() {
        impl = new CleanerImpl();
    }

	// 创建一个新的 Cleaner，使用默认后台守护线程处理清理任务。
    public static Cleaner create() {
        Cleaner cleaner = new Cleaner();
        cleaner.impl.start(cleaner, null);
        return cleaner;
    }

	// 使用指定线程工厂创建 Cleaner，适合自定义线程配置（如优先级、命名）。
    public static Cleaner create(ThreadFactory threadFactory) {
        Objects.requireNonNull(threadFactory, "threadFactory");
        Cleaner cleaner = new Cleaner();
        cleaner.impl.start(cleaner, threadFactory);
        return cleaner;
    }

	// 注册一个对象与清理任务，当对象被 GC 回收后，后台线程执行 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);
    }

	// 表示一次清理任务，调用 clean() 方法可以手动执行清理逻辑，只会执行一次。
    public interface Cleanable {
        void clean();
    }

}