生产者消费者问题（java实现）

1、生产者、消费者模型（若容器容量为1）

生产者线程：

if(a ==1) {

wait()

}

a++;

notify;

消费者：

if (a == 0) {

wait();

}

a--;

notify;

2、下面是一个代码实现（简单的缓存容量只有1，即：若容器中有一个了，就不能再生产了）：

（1）最基本的写法：

资源类：（资源类或者共享对象一般都写成一个单独的类，然后在线程中实现共享）

public class Sample {

private int a;

public synchronized void increase() {

if (a != 0) {

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

a++;

notify();

System.out.println(a);

}

public synchronized void decrease() {

if (a == 0) {

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

a--;

notify();

System.out.println(a);

}

}

线程类：

生产者线程类：

public class IncreaseThread extends Thread {

private Sample sample;

public IncreaseThread(Sample sample) {

this.sample = sample;

}

@Override

public void run() {

while (true) {

try {

sleep(1000);

} catch (InterruptedException e) {

e.printStackTrace();

}

sample.increase();

}

}

}

消费者线程类：

public class DecreaseThread extends Thread {

private Sample sample;

public DecreaseThread(Sample sample) {

this.sample = sample;

}

@Override

public void run() {

while (true) {

try {

sleep(1000);

} catch (InterruptedException e) {

e.printStackTrace();

}

sample.decrease();

}

}

}

客户端测试类：

public class Test {

public static void main(String[] args) {

Sample sample = new Sample();

IncreaseThread increaseThread = new IncreaseThread(sample);

DecreaseThread decreaseThread = new DecreaseThread(sample);

increaseThread.start();

decreaseThread.start();

}

}

输出：

1

0

1

0

1

0

（2）这里存在一个问题，就是当有多个生产者和消费和消费者线程的时候，就会出现问题，输出的值并不一致是1 0 1 0。具体问题原因可以用代码具体分析一下。

解决方案：

资源类：

public class Sample {

private int a;

public synchronized void increase() {

while(a != 0) {

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

a++;

notify();

System.out.println(a);

}

public synchronized void decrease() {

while(a == 0) {

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

a--;

notify();

System.out.println(a);

}

}

客户端类

public class Test {

public static void main(String[] args) {

Sample sample = new Sample();

IncreaseThread increaseThread = new IncreaseThread(sample);

DecreaseThread decreaseThread = new DecreaseThread(sample);

IncreaseThread increaseThread2 = new IncreaseThread(sample);

DecreaseThread decreaseThread2= new DecreaseThread(sample);

increaseThread.start();

decreaseThread.start();

increaseThread2.start();

decreaseThread2.start();

}

}

说明，一般都用while；(这里用if代码片段，纯粹是为了过度)

3、代码升级，容器容量是number=5;

和上面相比，仅需修改如下代码：

public class Sample {

public static int number = 5;

private int a;

public synchronized void increase() {

while (a >= 5){

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

a++;

notify();

System.out.println(a);

}

public synchronized void decrease() {

while (a <= 0) {

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

a--;

notify();

System.out.println(a);

}

}