java.lang.Void

最新推荐文章于 2021-03-11 11:35:06 发布

zhang284021445

最新推荐文章于 2021-03-11 11:35:06 发布

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分类专栏： JAVA 文章标签： java.lang.Void占位符类

本文链接：https://blog.youkuaiyun.com/zhang284021445/article/details/84902153

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本文深入探讨了java.util.concurrent包下ForkJoinPool类及其内部类EmptyTask的具体实现与用途。EmptyTask作为占位符任务，在ForkJoinPool的工作队列中扮演重要角色，确保并发操作正确执行。

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java.util.concurrent.ForkJoinPool
/**
 * Class for artificial tasks that are used to replace the target
 * of local joins if they are removed from an interior queue slot
 * in WorkQueue.tryRemoveAndExec. We don't need the proxy to
 * actually do anything beyond having a unique identity.
 */
static final class EmptyTask extends ForkJoinTask<Void> {
    private static final long serialVersionUID = -7721805057305804111L;
    EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
public final Void getRawResult() { return null; }
    public final void setRawResult(Void x) {}
    public final boolean exec() { return true; }
}

java.lang.Void类是一个不可实例化（构造函数私有）的占位符类，它持有Java关键字void的Class对象的引用

package java.lang;

/**
 * The {@code Void} class is an uninstantiable placeholder class to hold a
 * reference to the {@code Class} object representing the Java keyword
 * void.
 *
 * @author  unascribed
 * @since   JDK1.1
 */
public final
class Void {

    /**
     * The {@code Class} object representing the pseudo-type corresponding to
     * the keyword {@code void}.
     */
@SuppressWarnings("unchecked")
    public static final Class<Void> TYPE = (Class<Void>) Class.getPrimitiveClass("void");

    /*
     * The Void class cannot be instantiated.
     */
private Void() {}
}