原文链接：http://www.cnblogs.com/happyPawpaw/archive/2013/01/18/2865957.html
java实现生产者消费者问题
引言
生产者和消费者问题是线程模型中的经典问题：生产者和消费者在同一时间段内共用同一个存储空间，如下图所示，生产者向空间里存放数据，而消费者取用数据，如果不加以协调可能会出现以下情况：
生产者消费者图
存储空间已满，而生产者占用着它，消费者等着生产者让出空间从而去除产品，生产者等着消费者消费产品，从而向空间中添加产品。互相等待，从而发生死锁。
JAVA解决线程模型的三种方式
1、wait()和notify()
import java.util.LinkedList;
public class ProducerConsumer {
private LinkedList<Object> storeHouse = new LinkedList<Object>();
private int MAX = 10;
public ProducerConsumer() {
}
public void start() {
new Producer().start();
new Comsumer().start();
}
class Producer extends Thread {
public void run() {
while (true) {
synchronized (storeHouse) {
try {
while (storeHouse.size() == MAX) {
System.out.println("storeHouse is full , please wait");
storeHouse.wait();
}
Object newOb = new Object();
if (storeHouse.add(newOb)) {
System.out.println("Producer put a Object to storeHouse");
Thread.sleep((long) (Math.random() * 3000));
storeHouse.notify();
}
} catch (InterruptedException ie) {
System.out.println("producer is interrupted!");
}
}
}
}
}
class Comsumer extends Thread {
public void run() {
while (true) {
synchronized (storeHouse) {
try {
while (storeHouse.size() == 0) {
System.out.println("storeHouse is empty , please wait");
storeHouse.wait();
}
storeHouse.removeLast();
System.out.println("Comsumer get a Object from storeHouse");
Thread.sleep((long) (Math.random() * 3000));
storeHouse.notify();
} catch (InterruptedException ie) {
System.out.println("Consumer is interrupted");
}
}
}
}
}
public static void main(String[] args) throws Exception {
ProducerConsumer pc = new ProducerConsumer();
pc.start();
}
}
2、await()和signal()，即线程锁的方式
package sort;
import java.util.LinkedList;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class ProducerConsumer {
private LinkedList<Object> myList = new LinkedList<Object>();
private int MAX = 10;
private final Lock lock = new ReentrantLock();
private final Condition full = lock.newCondition();
private final Condition empty = lock.newCondition();
public ProducerConsumer() {
}
public void start() {
new Producer().start();
new Consumer().start();
}
public static void main(String[] args) throws Exception {
ProducerConsumer s2 = new ProducerConsumer();
s2.start();
}
class Producer extends Thread {
public void run() {
while (true) {
lock.lock();
try {
while (myList.size() == MAX) {
System.out.println("warning: it's full!");
full.await();
}
Object o = new Object();
if (myList.add(o)) {
System.out.println("Producer: " + o);
empty.signal();
}
} catch (InterruptedException ie) {
System.out.println("producer is interrupted!");
} finally {
lock.unlock();
}
}
}
}
class Consumer extends Thread {
public void run() {
while (true) {
lock.lock();
try {
while (myList.size() == 0) {
System.out.println("warning: it's empty!");
empty.await();
}
Object o = myList.removeLast();
System.out.println("Consumer: " + o);
full.signal();
} catch (InterruptedException ie) {
System.out.println("consumer is interrupted!");
} finally {
lock.unlock();
}
}
}
}
}
3、阻塞队列的方式
import java.util.concurrent.*;
public class ProducerConsumer {
// 建立一个阻塞队列
private LinkedBlockingQueue<Object> queue = new LinkedBlockingQueue<Object>(10);
public ProducerConsumer() {
}
public void start() {
new Producer().start();
new Consumer().start();
}
public static void main(String[] args) throws Exception {
ProducerConsumer s3 = new ProducerConsumer();
s3.start();
}
class Producer extends Thread {
public void run() {
while (true) {
try {
Object o = new Object();
// 取出一个对象
queue.put(o);
System.out.println("Producer: " + o);
} catch (InterruptedException e) {
System.out.println("producer is interrupted!");
}
// }
}
}
}
class Consumer extends Thread {
public void run() {
while (true) {
try {
// 取出一个对象
Object o = queue.take();
System.out.println("Consumer: " + o);
} catch (InterruptedException e) {
System.out.println("producer is interrupted!");
}
// }
}
}
}
}
结论
三种方式原理一致，都是对独占空间加锁，阻塞和唤醒线程，第一种方式比较传统，第三种方式最简单，只需存储和取用，线程同步的操作交由LinkedBlockingQueue全权处理。
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使用lock/condition实现生产者消费者模式如下：
import java.util.Date; import java.util.LinkedList; import java.util.List; import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; class Buffer { private final Lock lock; private final Condition notFull; private final Condition notEmpty; private int maxSize; private List<Date> storage; Buffer(int size){ //使用锁lock，并且创建两个condition，相当于两个阻塞队列 lock=new ReentrantLock(); notFull=lock.newCondition(); notEmpty=lock.newCondition(); maxSize=size; storage=new LinkedList<>(); } public void put() { lock.lock(); try { while (storage.size() ==maxSize ){//如果队列满了 System.out.print(Thread.currentThread().getName()+": wait \n");; notFull.await();//阻塞生产线程 } storage.add(new Date()); System.out.print(Thread.currentThread().getName()+": put:"+storage.size()+ "\n"); Thread.sleep(1000); notEmpty.signalAll();//唤醒消费线程 } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ lock.unlock(); } } public void take() { lock.lock(); try { while (storage.size() ==0 ){//如果队列满了 System.out.print(Thread.currentThread().getName()+": wait \n");; notEmpty.await();//阻塞消费线程 } Date d=((LinkedList<Date>)storage).poll(); System.out.print(Thread.currentThread().getName()+": take:"+storage.size()+ "\n"); Thread.sleep(1000); notFull.signalAll();//唤醒生产线程 } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ lock.unlock(); } } } class Producer implements Runnable{ private Buffer buffer; Producer(Buffer b){ buffer=b; } @Override public void run() { while(true){ buffer.put(); } } } class Consumer implements Runnable{ private Buffer buffer; Consumer(Buffer b){ buffer=b; } @Override public void run() { while(true){ buffer.take(); } } } public class Main{ public static void main(String[] arg){ Buffer buffer=new Buffer(10); Producer producer=new Producer(buffer); Consumer consumer=new Consumer(buffer); for(int i=0;i<3;i++){ new Thread(producer,"producer-"+i).start(); } for(int i=0;i<3;i++){ new Thread(consumer,"consumer-"+i).start(); } } }
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