单选题 分析代码.下面陈述正确的是 ?import java.util.*;public class Test { private Stack stack = new Stack(); private int i = 0; public static void main(String[] args) { new Test(); } public Test() { new Producer().start(); new Consumer().start(); } class Producer extends Thread { public void run() { while (true) { System.out.println("Producer: put " + i); stack.push(new Integer(i++)); synchronized (stack) { notifyAll(); } } } } class Consumer extends Thread { public void run() { while (true) { synchronized (stack) { try { while (stack.isEmpty()) stack.wait(); System.out.println("Consumer: get " + stack.pop()); } catch (InterruptedException ex) { ex.printStackTrace(); } } } } }}