深入理解独占锁ReentrantLock类锁( 二 ) _生活百科

2）由于可控的原因我们甚至可以多个条件队列来进行对线程调控。
注意：调用Condition的await()和signal()方法，都必须在lock保护之内。
@Slf4jpublic class ReentrantLockDemo {private static ReentrantLock lock = new ReentrantLock();private static Condition cigCon = lock.newCondition();private static Condition takeCon = lock.newCondition();private static boolean hashcig = false;private static boolean hastakeout = false;//送烟public void cigratee(){lock.lock();try {while(!hashcig){try {log.debug("没有烟，歇一会");cigCon.await();}catch (Exception e){e.printStackTrace();}}log.debug("有烟了，干活");}finally {lock.unlock();}}//送外卖public void takeout(){lock.lock();try {while(!hastakeout){try {log.debug("没有饭，歇一会");takeCon.await();}catch (Exception e){e.printStackTrace();}}log.debug("有饭了，干活");}finally {lock.unlock();}}public static void main(String[] args) {ReentrantLockDemo6 test = new ReentrantLockDemo6();new Thread(() ->{test.cigratee();}).start();new Thread(() -> {test.takeout();}).start();new Thread(() ->{lock.lock();try {hashcig = true;log.debug("唤醒送烟的等待线程");cigCon.signal();}finally {lock.unlock();}},"t1").start();new Thread(() ->{lock.lock();try {hastakeout = true;log.debug("唤醒送饭的等待线程");takeCon.signal();}finally {lock.unlock();}},"t2").start();}}ReentrantLock源码分析（版本为jdk14）【0】前置部分最好有关于JDK实现管程的了解【可查看深入理解AQS--jdk层面管程实现】
【1】ReentrantLock类自身部分
0）继承关系
//锁的接口定义，定义了一个锁该具备哪一些功能public interface Lock {void lock();void lockInterruptibly() throws InterruptedException;boolean tryLock();boolean tryLock(long time, TimeUnit unit) throws InterruptedException;void unlock();Condition newCondition();}1）属性值
//同步器句柄，同步器提供了所有的实现机制private final Sync sync;2）构造方法
//默认是采用非公平的同步器public ReentrantLock() {sync = new NonfairSync();}//此外可以根据传入的参数选择同步器public ReentrantLock(boolean fair) {sync = fair ? new FairSync() : new NonfairSync();}3）其他方法【看完之后，你会发现，其实ReentrantLock什么事都不干，统统都交给了持有的AQS同步器去干活了，有一种修饰器设计模式的味道，只是包装了一下，具体内部的同步器类型由自己选择，所以同步器显得就很重要】
public class ReentrantLock implements Lock, java.io.Serializable {.....//获取锁定public void lock() {sync.lock();}//中断式的加锁，如果没有被中断就会加锁public void lockInterruptibly() throws InterruptedException {sync.lockInterruptibly();}//仅当在调用时锁不被另一个线程持有时才获取锁public boolean tryLock() {return sync.tryLock();}//超时加锁，限定加锁时间public boolean tryLock(long timeout, TimeUnit unit) throws InterruptedException {return sync.tryLockNanos(unit.toNanos(timeout));}//尝试释放此锁public void unlock() {sync.release(1);}//返回一个用于此锁定实例的条件实例，说白了就是监视器public Condition newCondition() {return sync.newCondition();}//查询当前线程在此锁上保留的数量public int getHoldCount() {return sync.getHoldCount();}public boolean isHeldByCurrentThread() {return sync.isHeldExclusively();}//判断同步器是否在被持有状态，也就是被加锁了public boolean isLocked() {return sync.isLocked();}//判断同步器的类型public final boolean isFair() {return sync instanceof FairSync;}protected Thread getOwner() {return sync.getOwner();}public final boolean hasQueuedThreads() {return sync.hasQueuedThreads();}//判断同步器里面是否有该线程public final boolean hasQueuedThread(Thread thread) {return sync.isQueued(thread);}public final int getQueueLength() {return sync.getQueueLength();}protected Collection<Thread> getQueuedThreads() {return sync.getQueuedThreads();}public boolean hasWaiters(Condition condition) {if (condition == null)throw new NullPointerException();if (!(condition instanceof AbstractQueuedSynchronizer.ConditionObject))throw new IllegalArgumentException("not owner");return sync.hasWaiters((AbstractQueuedSynchronizer.ConditionObject)condition);}//返回条件队列里面等待的线程的个数public int getWaitQueueLength(Condition condition) {if (condition == null)throw new NullPointerException();if (!(condition instanceof AbstractQueuedSynchronizer.ConditionObject))throw new IllegalArgumentException("not owner");return sync.getWaitQueueLength((AbstractQueuedSynchronizer.ConditionObject)condition);}//返回条件队列里面等待的线程protected Collection<Thread> getWaitingThreads(Condition condition) {if (condition == null)throw new NullPointerException();if (!(condition instanceof AbstractQueuedSynchronizer.ConditionObject))throw new IllegalArgumentException("not owner");return sync.getWaitingThreads((AbstractQueuedSynchronizer.ConditionObject)condition);}}

深入理解独占锁ReentrantLock类锁( 二 )

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