生产者消费者问题

public class ProducerConsumer {public Product[] products = new Product[10];volatile int top = 0;volatile int capacity = 0;public static final Integer HOLD = 0;class Producer implements Runnable {public void produce(int i) throws InterruptedException {synchronized(HOLD) {while (capacity == products.length) {System.out.println("products are full...");HOLD.wait();}Product p = new Product(i);products[top++] = p;System.out.println("Producer ：" + p);capacity++;Thread.sleep(500);HOLD.notifyAll();}}@Overridepublic void run() {try {int i = 0;for (;;) {produce(i);i++;}} catch (InterruptedException e) {e.printStackTrace();}}}class Consumer implements Runnable {public synchronized void consume() throws InterruptedException {while (!Thread.interrupted()) {synchronized(HOLD) {while (capacity == 0) {System.out.println("products is null....");HOLD.wait();}top--;Product p = products[top];System.out.println("Consumer : " + p);capacity--;Thread.sleep(500);HOLD.notifyAll();}}}@Overridepublic void run() {try {consume();} catch (InterruptedException e) {e.printStackTrace();}}}class Product {private int id;public Product(int id) {super();this.id = id;}@Overridepublic String toString() {return "Product [id = " + id + "]";}}public static void main(String[] args) {ProducerConsumer test = new ProducerConsumer();new Thread(test.new Producer()).start();new Thread(test.new Consumer()).start();}}

import java.util.concurrent.BlockingQueue;import java.util.concurrent.LinkedBlockingDeque;public class ProducerConsumer2 {public static void main(String[] args) {BlockingQueue<Integer> queue = new LinkedBlockingDeque<>();Producer p = new Producer(queue);Consumer<Integer> c1 = new Consumer<>(queue);Consumer<Integer> c2 = new Consumer<>(queue);new Thread(p).start();new Thread(c1).start();new Thread(c2).start();}}class Producer implements Runnable {private final BlockingQueue queue;private Integer i = 0;Producer(BlockingQueue q) {queue = q;}@Overridepublic void run() {while (true) {try {queue.put(produce());} catch (InterruptedException e) {e.printStackTrace();}}}private int produce() {try {Thread.sleep(500);System.out.println(Thread.currentThread().getName() + " produce " + (++i));} catch (InterruptedException e) {e.printStackTrace();}return i;}}class Consumer<K> implements Runnable {private final BlockingQueue<K> queue;Consumer(BlockingQueue<K> q) {queue = q;}@Overridepublic void run() {while (true) {try {consume(queue.take());} catch (InterruptedException e) {e.printStackTrace();}}}private void consume(K take) {System.out.println("---->" + Thread.currentThread().getName() + " consume " + take);}}

1、所有对象都自动含有单一的锁（也称监视器）。当在对象上调用其任意synchronized方法时，此对象被加锁，这是该对象的其他synchronized方法只有等到前一个方法调用完毕并释放了锁之后才能被调用。

2、对于某个特定对象来说，其所有的synchronized方法共享同一个锁。

3、调用sleep()的时候并没有释放锁，调用yield()方法也是这样。在wait()期间锁是释放的。

4、只能在同步控制方法或同步控制块中调用wait()、notify()和notifyAll()，sleep()可以在非同步控制方法里调用。

5、当notifyAll()因某个特定锁而被调用时，只有等待 这个锁的任务才会唤醒。

6、使用while循环包围wait()。

7、基本上，如果一个域可能会被多个任务同时访问，或者这些任务中至少有一个是写入任务，那么你就应该将这个域设置为volatile的。

8、volatile关键字确保了应用中的可视性。volatile域会被立即写入到主存中。

C语言版的生产者消费者参考如下网址：http://blog.csdn.net/zgrjkflmkyc/article/details/8971894

#include <string.h>#include <stdlib.h>#include <pthread.h>#include <stdio.h>/*********************************************************************实现生产者线程生产数据放入一个单向链表中，消费者线程负责消费数据*********************************************************************///单向链表数据结构struct product {charproduct_data[20];struct product*pre_product;struct product*next_product;};//向单向链表中加入一个节点（生产）。void addProduct(char *product_data);//从单向链表中取出全部节点信息（消费）。void consProduct();void consumer();//生产者执行生产任务void producer();#defineMAX 10#defineMIN 0volatile inttotal = 0;//max capacity = 10struct product*present_product = NULL;struct product*pre_product = NULL;intlock = 0;staticpthread_mutex_tmutex;staticpthread_cond_tcond;void addProduct(char *product_data) {pthread_mutex_lock(&mutex);while ( total == MAX ) {printf("Producer: I am waiting....\n");pthread_cond_wait(&cond, &mutex);}struct product *new_product = malloc(sizeof(struct product));if (present_product == NULL) {new_product -> pre_product = NULL;strcpy( new_product -> product_data, product_data);new_product -> next_product = NULL;present_product = new_product;total++;printf("produce data %s, total = %d\n", product_data, total);} else {new_product -> pre_product = present_product;strcpy( new_product -> product_data, product_data);new_product -> next_product = NULL;present_product -> next_product = new_product;present_product = new_product;total++;printf("produce data %s, total = %d\n", product_data, total);}sleep(1);pthread_mutex_unlock(&mutex);if (total == MIN + 1)pthread_cond_signal(&cond);//pthread_mutex_unlock(&mutex);}void consProduct() {pthread_mutex_lock(&mutex);while ( total == MIN ) {printf("Consumer: I am waiting....\n");pthread_cond_wait(&cond, &mutex);}if (present_product != NULL) {pre_product = present_product -> pre_product;printf("%s, total = %d\n", present_product -> product_data, total);if (pre_product != NULL) {pre_product -> next_product = 0;}free(present_product);present_product = pre_product;total--;}sleep(1);pthread_mutex_unlock(&mutex);if (total == MAX - 1)pthread_cond_signal(&cond);//pthread_mutex_unlock(&mutex);}void producer() {static int temp_i = 0;char temp[20] = { 0 };while( 1 ) {sprintf(temp, "number___%d", temp_i);addProduct(temp);temp_i++;}}void consumer() {while(1) {consProduct();printf("-------------\n");//usleep((int)(rand()/1000));}}int main() {intres;pthread_tthread_pro;pthread_tthread_cons;printf("create....\n");   //创建生产者线程。res = pthread_create(&thread_pro, NULL, (void *)producer, NULL);if ( res != 0 ) {perror("Thread producer creation failed.\n");exit(-1);}//创建消费者线程。res = pthread_create(&thread_cons, NULL, (void *)consumer, NULL);if ( res != 0 ) {perror("Thread consumer creation failed.\n");exit(-1);}res = pthread_mutex_init(&mutex, NULL);if (res != 0) {perror("Mutex initialization failed.");exit(-1);}res = pthread_cond_init(&cond, NULL);if (res != 0) {perror("Condition initialization failed.");exit(-1);}printf("Waiting for thread to finish...\n");res = pthread_join(thread_pro, NULL);if ( res != 0 ) {perror("Thread producer join failed.\n");exit(-1);}res = pthread_join(thread_cons, NULL);if ( res != 0 ) {perror("Thread consumer join failed.\n");exit(-1);}printf("finished!\n");return 0;}