java - CloneNotSupportedException即使实现Cloneable

为什么下面的代码在JDK7中抛出CloneNotSupportedException而在JDK6 中抛出而不是？

public class DemoThread extends Thread implements Cloneable {

    /**
     * @param args
     */
    public static void main(String[] args) {
        DemoThread t = new DemoThread();
        t.cloned();
    }

    public DemoThread cloned()
    {
        try {
            return (DemoThread) super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return null;
    }

}

最佳答案

这是SE 7中Thread的clone()的实现

/**
 * Throws CloneNotSupportedException as a Thread can not be meaningfully
 * cloned. Construct a new Thread instead.
 *
 * @throws  CloneNotSupportedException
 *          always
 */
@Override
protected Object clone() throws CloneNotSupportedException {
    throw new CloneNotSupportedException();
}

线程从未被设计为可克隆的。做一些阅读激发了我的评论之一，我发现这很好地总结了它:"But we eitherhave to disallow cloning or give it meaningful semantics - and thelatter isn't going to happen."-David Holmes