首先要知道 Java 中的锁主要分两类锁 , 一种是 synchronize锁 , 另外一种就是 J.U.C中 提供的锁 , J.U.C里核心的锁是 ReentrantLock
import com.mmall.concurrency.annoations.ThreadSafe;
import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 实例说明 模拟并发 发送5000 个请求 , 每次最多200 个请求 ,
* 每次计数自增1 , 最后结果应该是5000
*/
@Slf4j
@ThreadSafe
public class LockExample2 {
// 请求总数
public static int clientTotal = 5000;
// 同时并发执行的线程数
public static int threadTotal = 200;
public static int count = 0;
private final static Lock lock = new ReentrantLock();
public static void main(String[] args) throws Exception {
ExecutorService executorService = Executors.newCachedThreadPool();
final Semaphore semaphore = new Semaphore(threadTotal);
final CountDownLatch countDownLatch = new CountDownLatch(clientTotal);
for (int i = 0; i < clientTotal ; i++) {
executorService.execute(() -> {
try {
semaphore.acquire();
add();
semaphore.release();
} catch (Exception e) {
log.error("exception", e);
}
countDownLatch.countDown();
});
}
countDownLatch.await();
executorService.shutdown();
log.info("count:{}", count);
}
private static void add() {
lock.lock();
try {
count++;
} finally {
lock.unlock();
}
}
}
控制台输入时正确的, 结果为 5000