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线程6：生产者消费者模式

2017-08-17 22:18 211 查看
引言 生产者消费者要素

一采用synchronized锁以及wait notify方法实现
实体类

Producer线程类

Consumer线程类

测试类

运行结果

二采用Lock锁以及await signal方法实现
实体类

三采用BlockQueue实现

总结生产者消费者三种方式的核心代码模型
synchronized方式下模型

Lock锁方式下模型

BlockingQueue方式下模型

引言 生产者消费者要素

我们将生产者作为一个线程类、消费者作为一个线程类。那么生产方法、消费方法由谁来调用、生产消费的是什么，我们从这几点出发，总结出以下几个要写的类（类比
取钱/存钱
，和
账户类
）。

实体类
，其中写生产方法。消费方法。

Producer线程类
，
run方法
中调用实体类中的生产方法。

Consumer线程类
，
run方法
中调用实体类中的消费方法。

测试类，新建启动线程等。

一、采用synchronized锁以及wait notify方法实现

①实体类

class Person
{
private int foodNum = 0;
private Object synObj = new Object();

private final int MAX_NUM = 5;

public void produce() throws InterruptedException
{
synchronized (synObj)//①
{
while (foodNum == 5)//②
{
System.out.println("box is full，size = " + foodNum+",生产阻塞");
synObj.wait();//③
}
foodNum++;//④
System.out.println("produce success foodNum = " + foodNum);
synObj.notifyAll();//⑤
}

}

public void consume() throws InterruptedException
{
synchronized (synObj)
{
while (foodNum == 0)
{
System.out.println("box is empty,size = " + foodNum+",消费阻塞");
synObj.wait();
}
foodNum--;
System.out.println("consume success foodNum = " + foodNum);
synObj.notifyAll();
}

}
}


②Producer线程类

class Producer implements Runnable
{
private Person person;
private String producerName;

public Producer(String producerName, Person person)
{
this.producerName = producerName;
this.person = person;
}

@Override
public void run()
{
while (true)
{
try
{
person.produce();
} catch (InterruptedException e)
{
e.printStackTrace();
}
}
}

}


③Consumer线程类

class Consumer implements Runnable
{

private Person person;
private String consumerName;

public Consumer(String consumerName, Person person)
{
this.consumerName = consumerName;
this.person = person;
}

@Override
public void run()
{
try
{
person.consume();
} catch (InterruptedException e)
{
e.printStackTrace();
}

}

}


④测试类

public class Main1
{
public static void main(String[] args) throws IOException
{
Person person = new Person();
new Thread(new Consumer("消费者一", person)).start();
new Thread(new Consumer("消费者二", person)).start();
new Thread(new Consumer("消费者三", person)).start();

new Thread(new Producer("生产者一", person)).start();
new Thread(new Producer("生产者一", person)).start();
new Thread(new Producer("生产者一", person)).start();

}
}


运行结果

box is empty,size = 0,消费阻塞
box is empty,size = 0,消费阻塞
box is empty,size = 0,消费阻塞
produce success foodNum = 1
consume success foodNum = 0
produce success foodNum = 1
produce success foodNum = 2
produce success foodNum = 3
produce success foodNum = 4
produce success foodNum = 5
box is full，size = 5,生产阻塞
consume success foodNum = 4
consume success foodNum = 3
produce success foodNum = 4
produce success foodNum = 5
box is full，size = 5,生产阻塞
box is full，size = 5,生产阻塞
box is full，size = 5,生产阻塞


二、采用Lock锁以及await signal方法实现

仅仅修改实体类中的普通生产、消费方法。其他方法不变。

实体类

class Person
{
private int foodNum = 0;

private ReentrantLock lock = new ReentrantLock();//A1:Lock实例

private Condition condition = lock.newCondition();//A2：Condition实例

private final int MAX_NUM = 5;

public void produce()
{
lock.lock(); //B:加锁--try主体--finally释放锁流程
try
{
while (foodNum == MAX_NUM) //同上例
{
System.out.println(Thread.currentThread().getName()+
"box is full，size = " + foodNum+
",生产阻塞");
condition.await();
}
foodNum++;
System.out.println("produce success foodNum = " + foodNum);
condition.signalAll();
}
catch(InterruptedException e)
{
e.printStackTrace();
} finally
{
lock.unlock();
}

}

public void consume()
{
lock.lock();
try
{
while (foodNum == 0)
{
System.out.println(Thread.currentThread().getName()+
"box is empty,size = " + foodNum+
",消费阻塞");
condition.await();
}
foodNum--;
System.out.println("consume success foodNum = " + foodNum);
condition.signalAll();
}
catch(InterruptedException e)
{
e.printStackTrace();
} finally
{
lock.unlock();
}

}
}


消费者一box is empty,size = 0,消费阻塞
消费者二box is empty,size = 0,消费阻塞
produce success foodNum = 1
consume success foodNum = 0
消费者一box is empty,size = 0,消费阻塞
消费者二box is empty,size = 0,消费阻塞
produce success foodNum = 1
produce success foodNum = 2
consume success foodNum = 1
consume success foodNum = 0


三、采用BlockQueue实现

BlockingQueue
也是
java.util.concurrent
下的主要用来控制线程同步的工具。

BlockingQueue
有四个具体的实现类,根据不同需求,选择不同的实现类

ArrayBlockingQueue
：一个由数组支持的有界阻塞队列，规定大小的
BlockingQueue
,其构造函数必须带一个int参数来指明其大小.其所含的对象是以FIFO(先入先出)顺序排序的。

LinkedBlockingQueue
：大小不定的BlockingQueue,若其构造函数带一个规定大小的参数,生成的BlockingQueue有大小限制,若不带大小参数,所生成的BlockingQueue的大小由Integer.MAX_VALUE来决定.其所含的对象是以FIFO(先入先出)顺序排序的。

PriorityBlockingQueue
：类似于LinkedBlockQueue,但其所含对象的排序不是FIFO,而是依据对象的自然排序顺序或者是构造函数的
Comparator
决定的顺序。

SynchronousQueue
：特殊的BlockingQueue,对其的操作必须是放和取交替完成的。

LinkedBlockingQueue
可以指定容量，也可以不指定，不指定的话，默认最大是
Integer.MAX_VALUE
,其中主要用到
put
和
take
方法，
put
方法在队列满的时候会阻塞直到有队列成员被消费，
take
方法在队列空的时候会阻塞，直到有队列成员被放进来。

编写生产者、消费者、测试类：

import java.util.concurrent.BlockingQueue;

public class Producer implements Runnable {
BlockingQueue<String> queue;

public Producer(BlockingQueue<String> queue) {
this.queue = queue;
}

@Override
public void run() {
try {
String temp = "A Product, 生产线程："
+ Thread.currentThread().getName();
System.out.println("I have made a product:"
+ Thread.currentThread().getName());
queue.put(temp);//如果队列是满的话，会阻塞当前线程
} catch (InterruptedException e) {
e.printStackTrace();
}
}

}


import java.util.concurrent.BlockingQueue;

public class Consumer implements Runnable{
BlockingQueue<String> queue;

public Consumer(BlockingQueue<String> queue){
this.queue = queue;
}

@Override
public void run() {
try {
String temp = queue.take();//如果队列为空，会阻塞当前线程
System.out.println(Thread.currentThread().getName()+",正在消费："+temp);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}


import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;

public class Test3 {

public static void main(String[] args) {
BlockingQueue<String> queue = new LinkedBlockingQueue<String>(2);
// BlockingQueue<String> queue = new LinkedBlockingQueue<String>();
//不设置的话，LinkedBlockingQueue默认大小为Integer.MAX_VALUE

// BlockingQueue<String> queue = new ArrayBlockingQueue<String>(2);

Consumer consumer = new Consumer(queue);
Producer producer = new Producer(queue);
for (int i = 0; i < 5; i++) {
new Thread(producer, "Producer" + (i + 1)).start();

new Thread(consumer, "Consumer" + (i + 1)).start();
}
}
}


结果：

I have made a product:Producer1
I have made a product:Producer3
I have made a product:Producer2
Consumer1,正在消费：A Product, 生产线程：Producer1
I have made a product:Producer4
Consumer3,正在消费：A Product, 生产线程：Producer3
Consumer2,正在消费：A Product, 生产线程：Producer4
I have made a product:Producer5
Consumer5,正在消费：A Product, 生产线程：Producer2
Consumer4,正在消费：A Product, 生产线程：Producer5


总结：生产者消费者三种方式的核心代码模型

synchronized方式下模型

public void produce() / consume()
{
synchronized (synObj)//-----①同步对象
{
while (conditionfalse)//----②while条件
{
//show info or not
//③----wait阻塞，条件false不让执行
synObj.wait();
}
//条件符合开始执行
workSomething;
changeCondition;//④----执行完改变条件
System.out.println("produce success foodNum = " + foodNum);
synObj.notifyAll();//⑤----执行完毕通知其他的
}

}


Lock锁方式下模型

private ReentrantLock lock = new ReentrantLock();
private condition =lock.newCondition();

execute() / produce() / consume() {
lock.lock();
try{
while(conditionFalse){
condition.await();
}
//doSomething and change whileCondition;
condition.signalAll();
}catch(InterruptedException e){

}finally{
lock.unlock();
}
}


BlockingQueue方式下模型

//全局queue
BlockingQueue<T> bq=new ArrayBlockQueue<T>(n);
...

//生产者线程类中
@override
public void run(){
bq.put(e);//如果队列是满的话，会阻塞当前线程
}

//消费者线程类中
@override
public void run(){
bq.take();//如果队列是空的话，会阻塞当前线程
}
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标签：  线程 生产者与消费者模式
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