我正在尝试使用以下代码的线程执行一些生产者消费者 poc,并且在一轮之后两个线程都处于等待状态。 但我希望它们继续循环,其中一个线程不断增加计数器,其他线程不断减少。
有人可以建议我缺少什么吗?
public class ProducerConsumerWithThreads {
synchronized void withdrawBoxConsumer() {
if(box > 0){
box --;
System.out.println("Took one box now boxes left "+ box);
}
if(box == 0) {
System.out.println("Please put more boxes");
notify();
try{wait();}catch(Exception e){
System.out.println("Exception occured" + e.fillInStackTrace());
}
} else {
withdrawBoxConsumer();
}
}
synchronized void putBoxProducer() {
if(box < 10){
box ++;
System.out.println("Put one box now boxes are "+ box);
}
if(box == 10) {
System.out.println("Please Consume boxes");
notify();
try{wait();}catch(Exception e){
System.out.println("Exception occured" + e.fillInStackTrace());
}
} else {
putBoxProducer();
}
}
public int box = 5;
public static void main(String[] args) throws InterruptedException {
//pipeline of 10 boxes
//consumer takes one at a time .. till its empty
int boxLimit = 10;
final int box = 5;
final ProducerConsumerWithThreads c=new ProducerConsumerWithThreads();
new Thread(){
public void run(){c.withdrawBoxConsumer();}
}.start();
new Thread(){
public void run(){c.putBoxProducer();}
}.start();
}
}
我得到的输出是:
Took one box now boxes left 4
Took one box now boxes left 3
Took one box now boxes left 2
Took one box now boxes left 1
Took one box now boxes left 0
Please put more boxes
Put one box now boxes are 1
Put one box now boxes are 2
Put one box now boxes are 3
Put one box now boxes are 4
Put one box now boxes are 5
Put one box now boxes are 6
Put one box now boxes are 7
Put one box now boxes are 8
Put one box now boxes are 9
Put one box now boxes are 10
Please Consume boxes
我希望它能够按照逻辑进一步循环!有人可以帮忙吗?
最佳答案
您的问题是一个非常基本的流程问题:当调用“notify”并且等待的线程再次启动时,该方法完成并且线程停止运行。
请注意,您的两个方法在同一个对象上同步,因此它们永远不会同时运行。例如。一个线程将获取监视器,并递增/递减该框,直到它最终等待。然后另一个线程将继续,直到它等待。
在使用等待和通知时,您还遇到一些非常常见的其他问题。
synchronized void withdrawBoxConsumer() {
while( !Thread.currentThread().isInterrupted() ) {
if(box > 0){
box --;
System.out.println("Took one box now boxes left "+ box);
}
while(box == 0) {
System.out.println("Please put more boxes");
notifyAll();
try{
wait();
}catch(Exception e){
throw new RuntimeException(e);
}
}
}
}
synchronized void putBoxProducer() {
while( !Thread.currentThread().isInterrupted() ) {
if(box < 10){
box ++;
System.out.println("Put one box now boxes are "+ box);
}
while(box == 10) {
System.out.println("Please Consume boxes");
notifyAll();
try{
wait();
}catch(Exception e){
throw new RuntimeException(e);
}
}
}
}
- 我将其设为非递归,因为按照您的方式,堆栈会溢出。
- 由于虚假唤醒,等待条件处于循环状态。
- 我切换到
notifyAll
notify只会唤醒一个等待线程,在这种情况下应该没问题,但最好是安全一点。 box
理想情况下应该是并发类或 volatile 类,但由于您始终使用同步方法,所以应该没问题。- 同样,
box++
和box--
也是竞争条件。 e.fillInStackTrace()
不是您想要使用的。
关于java - 线程间通信生产者消费者问题,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/66075035/