用 wait-notify 写一段代码来解决生产者-消费者问题
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在同步块中调用 wait() 和 notify()方法,如果阻塞,通过循环来测试等待条件。请参考答案中的示例代码。
【生产者】
import java.util.Vector; import java.util.logging.Level; import java.util.logging.Logger; public class Producer implements Runnable { private final Vector sharedQueue; private final int SIZE; public Producer(Vector sharedQueue, int size) { this.sharedQueue = sharedQueue; this.SIZE = size; } @Override public void run() { // 生产数据 for (int i = 0; i < 7; i++) { System.out.println("Produced:" + i); try { produce(i); } catch (InterruptedException ex) { Logger.getLogger(Producer.class.getName()).log(Level.SEVERE, null, ex); } } } private void produce(int i) throws InterruptedException { // wait if queue is full while (sharedQueue.size() == SIZE) { synchronized (sharedQueue) { System.out.println("Queue is full " + Thread.currentThread().getName() + " is waiting , size: " + sharedQueue.size()); sharedQueue.wait(); } } // producing element and notify consumers synchronized (sharedQueue) { sharedQueue.add(i); sharedQueue.notifyAll(); } } }
【消费者】
import java.util.Vector; import java.util.logging.Level; import java.util.logging.Logger; public class Consumer implements Runnable { private final Vector sharedQueue; private final int SIZE; public Consumer(Vector sharedQueue, int size) { this.sharedQueue = sharedQueue; this.SIZE = size; } @Override public void run() { // 消费数据 while (true) { try { System.out.println("Consumer: " + consume()); Thread.sleep(50); } catch (InterruptedException ex) { Logger.getLogger(Consumer.class.getName()).log(Level.SEVERE, null, ex); } } } private int consume() throws InterruptedException { // wait if queue is empty while (sharedQueue.isEmpty()) { synchronized (sharedQueue) { System.out.println("Queue is empty " + Thread.currentThread().getName() + " is waiting , size: " + sharedQueue.size()); sharedQueue.wait(); } } //otherwise consume element and notify waiting producer synchronized (sharedQueue) { sharedQueue.notifyAll(); return (Integer) sharedQueue.remove(0); } } }
【测试函数】
import java.util.Vector; public class ProducerConsumerSolution { public static void main(String[] args) { Vector sharedQueue = new Vector(); int size = 4; Thread prodThread = new Thread(new Producer(sharedQueue, size), "Producer"); Thread consThread = new Thread(new Consumer(sharedQueue, size), "Consumer"); prodThread.start(); consThread.start(); } }
运行结果:
Produced:0
Queue is empty Consumer is waiting , size: 0
Produced:1
Consumer: 0
Produced:2
Produced:3
Produced:4
Produced:5
Queue is full Producer is waiting , size: 4
Consumer: 1
Produced:6
Queue is full Producer is waiting , size: 4
Consumer: 2
Consumer: 3
Consumer: 4
Consumer: 5
Consumer: 6
Queue is empty Consumer is waiting , size: 0
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