生产者消费者的notify和wait的问题

[叶不归宿lily]

红色那里，都是先wait(),再notify()。假设现在生产者生产的东西装满了篮子，那么它就会进入到while()循环里，然后wait()进入等待，请问进入等待后，它是怎么往下执行这个方法后面的notifyAll()这个方法的。不是进入等待了吗，怎么还可以往下执行。求大神回答，谢谢

public class ProducerConsumer {
public static void main(String[] args) {
SyncStack ss = new SyncStack();
Producer p = new Producer(ss);
Consumer c = new Consumer(ss);
new Thread(p).start();
new Thread(p).start();
new Thread(p).start();
new Thread(c).start();
}
}

class WoTou {
int id;
WoTou(int id) {
this.id = id;
}
public String toString() {
return "WoTou : " + id;
}
}

class SyncStack {
int index = 0;
WoTou[] arrWT = new WoTou[6];

public synchronized void push(WoTou wt) {
while(index == arrWT.length) {
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
this.notifyAll();
arrWT[index] = wt;
index ++;
}

public synchronized WoTou pop() {
while(index == 0) {
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
this.notifyAll();
index--;
return arrWT[index];
}
}

class Producer implements Runnable {
SyncStack ss = null;
Producer(SyncStack ss) {
this.ss = ss;
}

public void run() {
for(int i=0; i<20; i++) {
WoTou wt = new WoTou(i);
ss.push(wt);
System.out.println("生产了：" + wt);
try {
Thread.sleep((int)(Math.random() * 200));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}

class Consumer implements Runnable {
SyncStack ss = null;
Consumer(SyncStack ss) {
this.ss = ss;
}

public void run() {
for(int i=0; i<20; i++) {
WoTou wt = ss.pop();
System.out.println("消费了: " + wt);
try {
Thread.sleep((int)(Math.random() * 1000));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}

[abcdefghiijklmnopqrs]

wait方法会释放锁,其他方法就可以获取锁了