关于 Java 中生产者-消费者模型的问题
A question about Producer-Consumer Model in Java
我写了一个Java程序来解决多线程中的生产者消费者问题。但它不能正常工作。
节目:
public class ConsumerAndProducer {
static int products = 0;
static int capacity = 10;
public static void main(String[] args) {
new Thread(new Producer()).start();
new Thread(new Consumer()).start();
}
static class Consumer implements Runnable{
public void consume() {
synchronized (ConsumerAndProducer.class){
if(products <= 0){
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
products--;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Consumer, remain:" + products);
if(products == 9){
notify();
}
}
}
@Override
public void run() {
while(true){
consume();
}
}
}
static class Producer implements Runnable{
public void produce() {
synchronized (ConsumerAndProducer.class){
if(products == capacity){
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
products++;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Producer, remain:" + products);
if(products == 1){
notify();
}
}
}
@Override
public void run() {
while(true){
produce();
}
}
}
错误:
Producer, remain:1
Exception in thread "Thread-0" java.lang.IllegalMonitorStateException
at java.lang.Object.notify(Native Method)
at zhousai.ConsumerAndProducer$Producer.produce(ConsumerAndProducer.java:69)
at zhousai.ConsumerAndProducer$Producer.run(ConsumerAndProducer.java:77)
at java.lang.Thread.run(Thread.java:748)
Consumer, remain:0
Exception in thread "Thread-1" java.lang.IllegalMonitorStateException
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:502)
at zhousai.ConsumerAndProducer$Consumer.consume(ConsumerAndProducer.java:22)
at zhousai.ConsumerAndProducer$Consumer.run(ConsumerAndProducer.java:43)
at java.lang.Thread.run(Thread.java:748)
当我运行你的代码时,我得到了以下错误:
Exception in thread "Thread-0" java.lang.IllegalMonitorStateException: current thread is not owner
抛出该异常的代码行是对方法 wait()
.
的调用
您正在调用 class Producer
的方法 wait()
,但您正在 ConsumerAndProducer.class
上进行同步。 wait()
方法必须在您正在同步的对象上调用,因为该对象拥有锁,您必须在拥有锁的对象上调用 wait()
。因此出现错误消息:current thread not owner
.
最简单的解决方案是更改您的代码,这样您就可以调用 ConsumerAndProducer.class.wait()
而不仅仅是 wait()
.
这是你的代码和我建议的修复:
public class ConsumerAndProducer {
static int products = 0;
static int capacity = 10;
public static void main(String[] args) {
new Thread(new Producer()).start();
new Thread(new Consumer()).start();
}
static class Consumer implements Runnable {
public void consume() {
synchronized (ConsumerAndProducer.class){
if (products <= 0) {
try {
ConsumerAndProducer.class.wait(); // change here
} catch (InterruptedException e) {
e.printStackTrace();
}
}
products--;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Consumer, remain:" + products);
if(products == 9){
ConsumerAndProducer.class.notify(); // change here
}
}
}
@Override
public void run() {
while(true){
consume();
}
}
}
static class Producer implements Runnable{
public void produce() {
synchronized (ConsumerAndProducer.class){
if (products == capacity) {
try {
ConsumerAndProducer.class.wait(); // change here
} catch (InterruptedException e) {
e.printStackTrace();
}
}
products++;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Producer, remain:" + products);
if(products == 1){
ConsumerAndProducer.class.notify(); // change here
}
}
}
@Override
public void run() {
while(true){
produce();
}
}
}
}
我写了一个Java程序来解决多线程中的生产者消费者问题。但它不能正常工作。 节目:
public class ConsumerAndProducer {
static int products = 0;
static int capacity = 10;
public static void main(String[] args) {
new Thread(new Producer()).start();
new Thread(new Consumer()).start();
}
static class Consumer implements Runnable{
public void consume() {
synchronized (ConsumerAndProducer.class){
if(products <= 0){
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
products--;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Consumer, remain:" + products);
if(products == 9){
notify();
}
}
}
@Override
public void run() {
while(true){
consume();
}
}
}
static class Producer implements Runnable{
public void produce() {
synchronized (ConsumerAndProducer.class){
if(products == capacity){
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
products++;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Producer, remain:" + products);
if(products == 1){
notify();
}
}
}
@Override
public void run() {
while(true){
produce();
}
}
}
错误:
Producer, remain:1
Exception in thread "Thread-0" java.lang.IllegalMonitorStateException
at java.lang.Object.notify(Native Method)
at zhousai.ConsumerAndProducer$Producer.produce(ConsumerAndProducer.java:69)
at zhousai.ConsumerAndProducer$Producer.run(ConsumerAndProducer.java:77)
at java.lang.Thread.run(Thread.java:748)
Consumer, remain:0
Exception in thread "Thread-1" java.lang.IllegalMonitorStateException
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:502)
at zhousai.ConsumerAndProducer$Consumer.consume(ConsumerAndProducer.java:22)
at zhousai.ConsumerAndProducer$Consumer.run(ConsumerAndProducer.java:43)
at java.lang.Thread.run(Thread.java:748)
当我运行你的代码时,我得到了以下错误:
Exception in thread "Thread-0" java.lang.IllegalMonitorStateException: current thread is not owner
抛出该异常的代码行是对方法 wait()
.
的调用
您正在调用 class Producer
的方法 wait()
,但您正在 ConsumerAndProducer.class
上进行同步。 wait()
方法必须在您正在同步的对象上调用,因为该对象拥有锁,您必须在拥有锁的对象上调用 wait()
。因此出现错误消息:current thread not owner
.
最简单的解决方案是更改您的代码,这样您就可以调用 ConsumerAndProducer.class.wait()
而不仅仅是 wait()
.
这是你的代码和我建议的修复:
public class ConsumerAndProducer {
static int products = 0;
static int capacity = 10;
public static void main(String[] args) {
new Thread(new Producer()).start();
new Thread(new Consumer()).start();
}
static class Consumer implements Runnable {
public void consume() {
synchronized (ConsumerAndProducer.class){
if (products <= 0) {
try {
ConsumerAndProducer.class.wait(); // change here
} catch (InterruptedException e) {
e.printStackTrace();
}
}
products--;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Consumer, remain:" + products);
if(products == 9){
ConsumerAndProducer.class.notify(); // change here
}
}
}
@Override
public void run() {
while(true){
consume();
}
}
}
static class Producer implements Runnable{
public void produce() {
synchronized (ConsumerAndProducer.class){
if (products == capacity) {
try {
ConsumerAndProducer.class.wait(); // change here
} catch (InterruptedException e) {
e.printStackTrace();
}
}
products++;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Producer, remain:" + products);
if(products == 1){
ConsumerAndProducer.class.notify(); // change here
}
}
}
@Override
public void run() {
while(true){
produce();
}
}
}
}