使用semaphore实现生产者-消费者简单模型

代码很简单，就不介绍了。需要注意的是，先有生产才有消费，所以与消费者关联的semaphore计数开始为0，而与生产者关联的semaphore计数开始为1。

实现：

import java.util.concurrent.Semaphore;

/**
*
* Multithreading: consumer-producer model using semaphores
*
* @author ljs
* 2011-08-19
*
*/
public class ConsumerProducer {
//consumer-producer model
static class SharedData{
int data = 0;
Semaphore semproducer = new Semaphore(1);
//set initial count to 0, so a consumer needs to wait until data is available
Semaphore semconsumer = new Semaphore(0);

public int consume() throws InterruptedException{
try {
semconsumer.acquire();
System.out.format("    Consumed: %d%n", data);
Thread.sleep(10);
return data;
} catch (InterruptedException e) {
throw e;
} finally{
semproducer.release();
}
}

public void produce(int data) throws InterruptedException{
try {
semproducer.acquire();
this.data = data;
System.out.format("Produced: %d%n", data);
Thread.sleep(10);
} catch (InterruptedException e) {
throw e;
} finally{
semconsumer.release();
}
}
}
//consumer
static class ConsumerThread implements Runnable  {

private SharedData shared;

public ConsumerThread(SharedData shared){
this.shared=shared;
}

public void run(){
for(int i=0;i<30;i++){
try {
int data = shared.consume();
//use data
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
//producer
static class ProducerThread implements Runnable{
private SharedData shared;
public ProducerThread(SharedData shared){
this.shared=shared;
}
public void run(){
for(int i=0;i<30;i++){
try {
shared.produce(i);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}

public static void main(String[] args) throws Exception {
SharedData shared = new SharedData();

Thread producer = new Thread(new ProducerThread(shared),"producer");
Thread consumer = new Thread(new ConsumerThread(shared),"consumer");

consumer.start();
producer.start();
}

}

测试输出：

Produced: 0

Consumed: 0

Produced: 1

Consumed: 1

Produced: 2

Consumed: 2

Produced: 3

Consumed: 3

Produced: 4

Consumed: 4

Produced: 5

Consumed: 5

Produced: 6

Consumed: 6

Produced: 7

Consumed: 7

Produced: 8

Consumed: 8

Produced: 9

Consumed: 9

Produced: 10

Consumed: 10

Produced: 11

Consumed: 11

Produced: 12

Consumed: 12

Produced: 13

Consumed: 13

Produced: 14

Consumed: 14

Produced: 15

Consumed: 15

Produced: 16

Consumed: 16

Produced: 17

Consumed: 17

Produced: 18

Consumed: 18

Produced: 19

Consumed: 19

Produced: 20

Consumed: 20

Produced: 21

Consumed: 21

Produced: 22

Consumed: 22

Produced: 23

Consumed: 23

Produced: 24

Consumed: 24

Produced: 25

Consumed: 25

Produced: 26

Consumed: 26

Produced: 27

Consumed: 27

Produced: 28

Consumed: 28

Produced: 29

Consumed: 29