在 Java 中，Lock 接口的实现类ReentrantLock 类提供了比使用 synchronized 方法和代码块更广泛的锁定机制。


简单示例：

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;public class ReentrantLockExample {private final Lock lock = new ReentrantLock();private int counter = 0;public void increment() {lock.lock();try {counter++;} finally {lock.unlock();}}public int getCounter() {lock.lock();try {return counter;} finally {lock.unlock();}}public static void main(String[] args) {ReentrantLockExample example = new ReentrantLockExample();example.increment();System.out.println("Counter: " + example.getCounter());}
}

生产者-消费者示例：

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.LinkedList;
import java.util.Queue;public class ProducerConsumer {private final Queue<Integer> queue = new LinkedList<>();private final int CAPACITY = 5;private final Lock lock = new ReentrantLock();private final Condition notFull = lock.newCondition();private final Condition notEmpty = lock.newCondition();public void produce() throws InterruptedException {int value = 0;while (true) {lock.lock();try {while (queue.size() == CAPACITY) {notFull.await();}queue.add(value);System.out.println("Produced " + value);value++;notEmpty.signal();} finally {lock.unlock();}Thread.sleep(1000); // Simulate time taken to produce an item}}public void consume() throws InterruptedException {while (true) {lock.lock();try {while (queue.isEmpty()) {notEmpty.await();}int value = queue.poll();System.out.println("Consumed " + value);notFull.signal();} finally {lock.unlock();}Thread.sleep(1500); // Simulate time taken to consume an item}}public static void main(String[] args) {ProducerConsumer pc = new ProducerConsumer();Thread producerThread = new Thread(() -> {try {pc.produce();} catch (InterruptedException e) {Thread.currentThread().interrupt();}});Thread consumerThread = new Thread(() -> {try {pc.consume();} catch (InterruptedException e) {Thread.currentThread().interrupt();}});producerThread.start();consumerThread.start();}
}