Answers
他与传统的synchronized的区别有:
1.ReentranLock的内部实现使用了AbstractQueuedSynchronizer(等待队列) 所以他能够做到tryLock()、getLockQueueLength()以及中断阻塞这些操作 这些是synchronized做不到的
2.使用Condition代替了原有的Object监视器方法的使用 使被监视的对象与Lock本身的关系不再是一对一 变成了一对多(一个Lock可以拥有多个Condition 而synchronized只能对一个Object做监听)
...那个啥 API上说的挺详细的 我就不多说了
例子 随手写的 再次叮嘱楼主自己看API
package thread;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
public class ReentrantLockTester {
private static final ReentrantLock REENTRANT_LOCK = new ReentrantLock(false);
private static final Condition CONDITION_1 = REENTRANT_LOCK.newCondition();
private static final Condition CONDITION_2 = REENTRANT_LOCK.newCondition();
public static void main(String[] args) throws Exception {
Thread t1 = new Thread(new Task1());
Thread t2 = new Thread(new Task2());
t1.start();
TimeUnit.SECONDS.sleep(2);
t2.start();
TimeUnit.SECONDS.sleep(2);
t2.interrupt();// 取消线程2的阻塞
for (int i = 0; i < 5; i++) {
new Thread(new Task2()).start();
}
for (int i = 0; i < 5; i++) {
new Thread(new Task3()).start();
}
TimeUnit.SECONDS.sleep(5);// 等待五秒 让上面的线程全部进入等待状态
REENTRANT_LOCK.lock();
CONDITION_1.signalAll();// 唤醒等待在条件1上的线程
TimeUnit.SECONDS.sleep(5);// 分批唤醒
CONDITION_2.signalAll();// 唤醒等待在条件2上的线程
REENTRANT_LOCK.unlock();
}
static class Task1 implements Runnable {
public void run() {
try {
REENTRANT_LOCK.lockInterruptibly();
System.err.println("Task1获取锁定" + Thread.currentThread().getId());
TimeUnit.SECONDS.sleep(10);
} catch (InterruptedException e) {
System.err.println("Task1被中断了呢 啊哈哈哈~" + Thread.currentThread().getId());
} finally {
if (REENTRANT_LOCK.isHeldByCurrentThread()) {
REENTRANT_LOCK.unlock();
}
}
}
}
static class Task2 implements Runnable {
public void run() {
try {
REENTRANT_LOCK.lockInterruptibly();
System.err.println("Task2获取锁定" + Thread.currentThread().getId());
CONDITION_1.await();
System.err.println("Task2被唤醒了哦~" + Thread.currentThread().getId());
} catch (InterruptedException e) {
System.err.println("Task2被中断了呢 啊哈哈哈~" + Thread.currentThread().getId());
} finally {
if (REENTRANT_LOCK.isHeldByCurrentThread()) {
REENTRANT_LOCK.unlock();
}
}
}
}
static class Task3 implements Runnable {
public void run() {
try {
REENTRANT_LOCK.lockInterruptibly();
System.err.println("Task3获取锁定" + Thread.currentThread().getId());
CONDITION_2.await();
System.err.println("Task3被唤醒了哦~" + Thread.currentThread().getId());
} catch (InterruptedException e) {
System.err.println("Task3被中断了呢 啊哈哈哈~" + Thread.currentThread().getId());
} finally {
if (REENTRANT_LOCK.isHeldByCurrentThread()) {
REENTRANT_LOCK.unlock();
}
}
}
}
}
塞尔达link
answered 12 years, 1 month ago