java 实现生产者-消费者模式

public class Depot { // 实际容量
private volatile int capacity = 0 ;
// 最大容量
private static final int MAX_CAPACITY = 100 ;
// 锁
private final Object lock = new Object() ; public Depot(){ } /**
* 生产
* @param: num
* @return:
*/
public void producer(int num) {
if(num<0){
System.out.println("生产数量不可为负数");
throw new IllegalArgumentException("生产数量不可为负数") ;
} synchronized (lock){
// 生产
int left = 0;
try {
left = doProducer(num); // 要求生产数量未达标，让出执行权
while (left > 0){
Thread.yield();
left = doProducer(left);
}
} catch (InterruptedException e) {
e.printStackTrace();
} lock.notify();
} } /**
* 实际生产逻辑
* @param: num
* @return: 返回未生产数量
*/
private int doProducer(int num) throws InterruptedException {
// 实际增加数量
int grow = num ;
// 未生产数量
int left = 0 ; // 等待仓库被消费
while (capacity>=MAX_CAPACITY){
lock.wait();
} // 计算实际新增数量
if( (num+capacity) > MAX_CAPACITY ){
grow = MAX_CAPACITY - capacity ;
left = num - grow ;
}
capacity += grow ; // 仓库已经生产，通知消费者消费
lock.notify();
System.out.println(Thread.currentThread().getName() + " Plan Producer = " + num + " Actually = " + grow + " left = " + left + " capacity = " + capacity);
return left ;
} /**
* 消费
* @param: num
* @return:
*/
public void consumer(int num) {
if(num<0){
System.out.println("消费数量不可为负数");
throw new IllegalArgumentException("消费数量不可为负数") ;
} synchronized (lock){
// 消费仓库
int left = 0;
try {
left = doConsumer(num); // 要求消费数量未达标，让出执行权
while (left > 0){
Thread.yield();
left = doConsumer(left);
}
} catch (InterruptedException e) {
e.printStackTrace();
} // 仓库已经被消费，通知生产者生产
lock.notify();
} } /**
* 实际消费逻辑
* @param: num
* @return: 剩余未消费数量
*/
private int doConsumer(int num) throws InterruptedException {
// 实际消费数量
int decrease = num ;
// 剩余未消费
int left = 0 ; // 等待仓库生产
while (capacity <= 0){
lock.wait();
} // 计算实际消费数量
if(decrease > capacity){
decrease = capacity ;
left = decrease - capacity ;
}
capacity -= decrease ; System.out.println(Thread.currentThread().getName() + " Plan Consumer = "+ num + " Actually = " + decrease + " left = " + left + " capacity = " + capacity );
return left ;
}}

public class ProducerAndConsumer {
public static void main(String[] args) throws InterruptedException {
Depot depot = new Depot() ; for(int x=0 ; x<4; x++){
new Thread(new Runnable() {
@Override public void run() {
depot.producer(40);
}
}).start();
} Thread.sleep(2000L);
for(int x=0 ; x<3; x++){
new Thread(new Runnable() {
@Override public void run() {
depot.consumer(40);
}
}).start();
} Thread.sleep(2000L); }
}

Thread-0 Plan Producer = 40 Actually = 40 left = 0 capacity = 40
Thread-1 Plan Producer = 40 Actually = 40 left = 0 capacity = 80
Thread-2 Plan Producer = 40 Actually = 20 left = 20 capacity = 100
Thread-4 Plan Consumer = 40 Actually = 40 left = 0 capacity = 60
Thread-2 Plan Producer = 20 Actually = 20 left = 0 capacity = 80
Thread-3 Plan Producer = 40 Actually = 20 left = 20 capacity = 100
Thread-6 Plan Consumer = 40 Actually = 40 left = 0 capacity = 60
Thread-5 Plan Consumer = 40 Actually = 40 left = 0 capacity = 20
Thread-3 Plan Producer = 20 Actually = 20 left = 0 capacity = 40