publicclassMainimplementsRunnable{privateintk;publicMain(){this.k=0;}publicMain(int_k){this.k=_k;}publicvoidrun(){inti=k;System.out.println();while(i<50){System.out.print(i+"");i+=2;}System.out.println(Thread.currentThread().getName()+"结束");}publicstaticvoidmain(String[]args){Threadthread_odd=newThread(newMain(1),"奇数线程");Threadthread_even=newThread(newMain(2),"偶数线程");//注释1:将thread_even的线程优先级设置为10thread_odd.start();//注释2System.out.println("currentThread:"+Thread.currentThread().getName());System.out.println("activeCount"+thread_odd.activeCount());}}上述代码中thread_odd.activeCount()的作用是（）？