通过线程ID获取线程

    public static Thread findThread(long threadId) {
        ThreadGroup group = Thread.currentThread().getThreadGroup();
        while(group != null) {
            Thread[] threads = new Thread[(int)(group.activeCount() * 1.2)];
            int count = group.enumerate(threads, true);
            for(int i = 0; i < count; i++) {
                if(threadId == threads[i].getId()) {
                    return threads[i];
                }
            }
            group = group.getParent();
        }
        return null;
    }