獲取Java VM中當前運行的所有線程

    /**
     *  獲取Java VM中當前運行的所有線程
     * @return
     */
    public static Thread[] findAllThreads() {
        ThreadGroup group = Thread.currentThread().getThreadGroup();
        ThreadGroup topGroup = group;
        // 遍歷線程組樹，獲取根線程組
        while (group != null) {
            topGroup = group;
            group = group.getParent();
        }
        // 激活的線程數加倍
        int estimatedSize = topGroup.activeCount() * 2;
        Thread[] slacks = new Thread[estimatedSize];
         //獲取根線程組的所有線程
        int actualSize = topGroup.enumerate(slacks);
        Thread[] threads = new Thread[actualSize];
        System.arraycopy(slacks, 0, threads, 0, actualSize);
        return threads;
    }