import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; import java.util.concurrent.locks.Condition; // 仓库 class Depot { private int capacity; // 仓库的容量 private int size; // 仓库的库存数量 private Lock lock; // 独占锁 private Condition fullCondtion; // 生产条件 private Condition emptyCondtion; // 消费条件 public Depot(int capacity) { this.capacity = capacity; this.size = 0; this.lock = new ReentrantLock(); this.fullCondtion = lock.newCondition(); this.emptyCondtion = lock.newCondition(); } public void produce(int val) { lock.lock(); try { // left 表示“想要生产的数量”(有可能生产量太多,需多次生产) int left = val; while (left > 0) { // 库存已满时,等待“消费者”消费产品。 while (size >= capacity) fullCondtion.await(); // 获取“实际生产的数量”(即库存中新增的数量) // 如果“库存”+“想要生产的数量”>“总的容量”,则“实际增量”=“总的容量”-“当前容量”。(此时填满仓库) // 否则“实际增量”=“想要生产的数量” int inc = (size+left)>capacity ? (capacity-size) : left; size += inc; left -= inc; System.out.printf("%s produce(%3d) --> left=%3d, inc=%3d, size=%3d\n", Thread.currentThread().getName(), val, left, inc, size); // 通知“消费者”可以消费了。 emptyCondtion.signal(); } } catch (InterruptedException e) { } finally { lock.unlock(); } } public void consume(int val) { lock.lock(); try { // left 表示“客户要消费数量”(有可能消费量太大,库存不够,需多次消费) int left = val; while (left > 0) { // 库存为0时,等待“生产者”生产产品。 while (size <= 0) emptyCondtion.await(); // 获取“实际消费的数量”(即库存中实际减少的数量) // 如果“库存”<“客户要消费的数量”,则“实际消费量”=“库存”; // 否则,“实际消费量”=“客户要消费的数量”。 int dec = (size<left) ? size : left; size -= dec; left -= dec; System.out.printf("%s consume(%3d) <-- left=%3d, dec=%3d, size=%3d\n", Thread.currentThread().getName(), val, left, dec, size); fullCondtion.signal(); } } catch (InterruptedException e) { } finally { lock.unlock(); } } public String toString() { return "capacity:"+capacity+", actual size:"+size; } }; // 生产者 class Producer { private Depot depot; public Producer(Depot depot) { this.depot = depot; } // 消费产品:新建一个线程向仓库中生产产品。 public void produce(final int val) { new Thread() { public void run() { depot.produce(val); } }.start(); } } // 消费者 class Customer { private Depot depot; public Customer(Depot depot) { this.depot = depot; } // 消费产品:新建一个线程从仓库中消费产品。 public void consume(final int val) { new Thread() { public void run() { depot.consume(val); } }.start(); } } public class LockTest3 { public static void main(String[] args) { Depot mDepot = new Depot(100); Producer mPro = new Producer(mDepot); Customer mCus = new Customer(mDepot); mPro.produce(60); mPro.produce(120); mCus.consume(90); mCus.consume(150); mPro.produce(110); } }
Lock与Condition实现生产者与消费者
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