/**

     *  获取Java VM中当前运行的所有线程

     * @return

     */

    public static Thread[] findAllThreads() {

        ThreadGroup group = Thread.currentThread().getThreadGroup();

        ThreadGroup topGroup = group;

        // 遍历线程组树，获取根线程组

        while (group != null) {

            topGroup = group;

            group = group.getParent();

        }

        // 激活的线程数加倍

        int estimatedSize = topGroup.activeCount() * 2;

        Thread[] slacks = new Thread[estimatedSize];

         //获取根线程组的所有线程

        int actualSize = topGroup.enumerate(slacks);

        Thread[] threads = new Thread[actualSize];

        System.arraycopy(slacks, 0, threads, 0, actualSize);

        return threads;

    }