java并发包顶层AQS(抽象的队列式的同步器)分析，结合ReentrantLock分析（源码分析）

package com.kailong.lock;import java.util.ArrayList;import java.util.Collection;import java.util.Date;import java.util.concurrent.TimeUnit;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.LockSupport;import sun.misc.Unsafe;/** * Created by Administrator on 2017/4/20. * 抽象的队列式的同步器 * 不同的自定义同步器争用共享资源的方式也不同。自定义同步器在实现时只需要实现共享资源state的获取与释放方式即可， * 至于具体线程等待队列的维护（如获取资源失败入队/唤醒出队等），AQS已经在顶层实现好了。 * 自定义同步器实现时主要实现以下几种方法：     isHeldExclusively()：该线程是否正在独占资源。只有用到condition才需要去实现它。     tryAcquire(int)：独占方式。尝试获取资源，成功则返回true，失败则返回false。    tryRelease(int)：独占方式。尝试释放资源，成功则返回true，失败则返回false。    tryAcquireShared(int)：共享方式。尝试获取资源。负数表示失败；0表示成功，但没有剩余可用资源；正数表示成功，且有剩余资源。    tryReleaseShared(int)：共享方式。尝试释放资源，成功则返回true，失败则返回false。 同步类在实现时一般都将自定义同步器（sync）定义为内部类，供自己使用；而同步类自己（Mutex）则实现某个接口，对外服务。当然 ，接口的实现要直接依赖sync，它们在语义上也存在某种对应关系！！ 而sync只用实现资源state的获取-释放方式tryAcquire-tryRelelase，至于线程的排队、等待、唤醒等， 上层的AQS都已经实现好了，我们不用关心。比如自己实现可重入独占锁 接下来将会分析源码 让大家理解这个过程 */public class AbstractQueuedSynchronizer extends AbstractOwnableSynchronizer implements  java.io.Serializable{    private static final long serialVersionUID = 7373984972572414691L;//序列化id    protected AbstractQueuedSynchronizer() { }//无参数改造方法    static final class Node{        /**         * 指示节点正在等待共享模式的标记         */        static final Node SHARED = new Node();        /**         *指示节点正在等待独占模式的标记         */        static final Node EXCLUSIVE = null;        /**         *waitStatus值指示线程已取消         */        static final int CANCELLED =  1;        /**         *waitStatus值表示后续线程需要开启         */        static final int SIGNAL    = -1;        /**         *waitStatus值表示线程正在等待状态         */        static final int CONDITION = -2;        /**         *值指示下一个acquireShared应无条件地传播         */        static final int PROPAGATE = -3;        /**         * 等待状态         */        volatile int waitStatus;        //前驱        volatile Node prev;        //后继        volatile Node next;        //线程        volatile Thread thread;        //下一个等待        Node nextWaiter;        /**         * 如果节点在共享模式下等待，则返回true。         * @return         */        final boolean isShared() {            return nextWaiter == SHARED;        }        /**         * 返回上一个节点，如果为null，则抛出NullPointerException。         *当前辈不能为null时使用。 空检查可以         *被淘汰，但目前是为了帮助虚拟机          * @返回此节点的前身         * @return         * @throws NullPointerException         */        final Node predecessor() throws NullPointerException {            Node p = prev;            if (p == null)                throw new NullPointerException();            else                return p;        }        Node() {    // 用于建立初始头或共享标记        }        Node(Thread thread, Node mode) {     //Used by addWaiter            this.nextWaiter = mode;            this.thread = thread;        }        Node(Thread thread, int waitStatus) { // 按条件使用            this.waitStatus = waitStatus;            this.thread = thread;        }    }        private transient volatile Node head;        private transient volatile Node tail;        private volatile int state;        protected final int getState() {            return state;        }        protected final void setState(int newState) {            state = newState;        }        protected final boolean compareAndSetState(int expect, int update) {            return unsafe.compareAndSwapInt(this, stateOffset, expect, update);        }        static final long spinForTimeoutThreshold = 1000L;    /**     * 　此方法用于将node加入队尾     * @param node     * @return     */        private Node enq(final Node node) {            //CAS"自旋"，直到成功加入队尾  链表操作 加入节点 分两种情况 一如果链表为空则设置为头结点 否则添加即可            //AtomicInteger.getAndIncrement()函数源码,之前分析的cas机制如此，CAS自旋volatile变量            for (;;) {                Node t = tail;                if (t == null) { // 必须初始化                    if (compareAndSetHead(new Node()))                        tail = head;                } else {                    node.prev = t;                    if (compareAndSetTail(t, node)) {                        t.next = node;                        return t;                    }                }            }        }    /**     * addWaiter()将该线程加入等待队列的尾部，并标记为独占模式；     * 此方法用于将当前线程加入到等待队列的队尾，并返回当前线程所在的结点     * @param mode     * @return     */        private Node addWaiter(Node mode) {            // //以给定模式构造结点。mode有两种：EXCLUSIVE（独占）和SHARED（共享）            Node node = new Node(Thread.currentThread(), mode);            // //尝试快速方式直接放到队尾。 这里只是很简单的链表操作只不过多线程 因此需要用cas机制            Node pred = tail;//头结点            if (pred != null) {                node.prev = pred;                if (compareAndSetTail(pred, node)) {//利用cas机制修改节点 因为多线程操作 所以利用cas保证线程安全                    pred.next = node;                    return node;                }            }            //上一步失败则通过enq入队。            enq(node);            return node;        }        private void setHead(Node node) {            head = node;            node.thread = null;            node.prev = null;        }    /**     * 此方法用于唤醒等待队列中下一个线程。下面是源码：     * @param node     */        private void unparkSuccessor(Node node) {            int ws = node.waitStatus;//这里，node一般为当前线程所在的结点。            if (ws < 0)                compareAndSetWaitStatus(node, ws, 0);//置零当前线程所在的结点状态，允许失败。            Node s = node.next;            if (s == null || s.waitStatus > 0) {//如果为空或已取消                s = null;                for (Node t = tail; t != null && t != node; t = t.prev)                    if (t.waitStatus <= 0)//从这里可以看出，<=0的结点，都是还有效的结点。                        s = t;            }            if (s != null)                LockSupport.unpark(s.thread);//唤醒        }    /**     * 释放   还是cas机制 一个大的自旋 然后修改即可     */        private void doReleaseShared() {            for (;;) {                Node h = head;                if (h != null && h != tail) {                    int ws = h.waitStatus;                    if (ws == Node.SIGNAL) {                        if (!compareAndSetWaitStatus(h, Node.SIGNAL, 0))                            continue;            // loop to recheck cases                        unparkSuccessor(h);//唤醒后继                    }                    else if (ws == 0 &&                            !compareAndSetWaitStatus(h, 0, Node.PROPAGATE))                        continue;                // loop on failed CAS                }                if (h == head)                   // loop if head changed                    break;            }        }    /**     * 此方法在setHead()的基础上多了一步，就是自己苏醒的同时，如果条件符合（     * 比如还有剩余资源），还会去唤醒后继结点，毕竟是共享模式！     　　doReleaseShared()我们留着下一小节的releaseShared()里来讲。     * @param node     * @param propagate     */        private void setHeadAndPropagate(Node node, int propagate) {            Node h = head;            setHead(node);//head指向自己            //如果还有剩余量，继续唤醒下一个邻居线程            if (propagate > 0 || h == null || h.waitStatus < 0 ||                    (h = head) == null || h.waitStatus < 0) {                Node s = node.next;                if (s == null || s.isShared())                    doReleaseShared();            }        }        private void cancelAcquire(Node node) {            if (node == null)                return;            node.thread = null;            Node pred = node.prev;            while (pred.waitStatus > 0)                node.prev = pred = pred.prev;            Node predNext = pred.next;            node.waitStatus = Node.CANCELLED;            if (node == tail && compareAndSetTail(node, pred)) {                compareAndSetNext(pred, predNext, null);            } else {                int ws;                if (pred != head &&                        ((ws = pred.waitStatus) == Node.SIGNAL ||                                (ws <= 0 && compareAndSetWaitStatus(pred, ws, Node.SIGNAL))) &&                        pred.thread != null) {                    Node next = node.next;                    if (next != null && next.waitStatus <= 0)                        compareAndSetNext(pred, predNext, next);                } else {                    unparkSuccessor(node);                }                node.next = node; // help GC            }        }        private static boolean shouldParkAfterFailedAcquire(Node pred, Node node) {            int ws = pred.waitStatus;//拿到前驱的状态            if (ws == Node.SIGNAL)                return true;// //如果已经告诉前驱拿完号后通知自己一下，那就可以安心休息了            if (ws > 0) {                /* 8             * 如果前驱放弃了，那就一直往前找，直到找到最近一个正常等待的状态，并排在它的后边。 9            * 注意：那些放弃的结点，由于被自己“加塞”到它们前边，它们相当于形成一个无引用链，注意垃圾回收              会进行可达性分析，稍后就会被保安大叔赶走了(GC回收)！10            */                do {                    node.prev = pred = pred.prev;                } while (pred.waitStatus > 0);                pred.next = node;            } else {                //如果前驱正常，那就把前驱的状态设置成SIGNAL，告诉它拿完号后通知自己一下。有可能失败，                compareAndSetWaitStatus(pred, ws, Node.SIGNAL);            }            return false;        }        static void selfInterrupt() {            Thread.currentThread().interrupt();        }    /**     * 如果线程找好安全休息点后，那就可以安心去休息了。此方法就是让线程去休息，真正进入等待状态。     * @return     */        private final boolean parkAndCheckInterrupt() {            LockSupport.park(this);            return Thread.interrupted();        }    /**     * acquireQueued()使线程在等待队列中获取资源，一直获取到资源后才返回。     * 如果在整个等待过程中被中断过，则返回true，否则返回false。     * 进入等待状态休息，直到其他线程彻底释放资源后唤醒自己，自己再拿到资源，然后就可以去干自己想干的事了     * 在等待队列中排队拿号     * @param node     * @param arg     * @return     */        final boolean acquireQueued(final Node node, int arg) {            boolean failed = true;//标记是否成功拿到资源            try {                boolean interrupted = false;//标记等待过程中是否被中断过                for (;;) {//加入自旋  不断操作                    final Node p = node.predecessor();//拿到前驱                    if (p == head && tryAcquire(arg)) {////拿到资源后，将head指向该结点。所以head所指的标杆结点，就是当前获取到资源的那个结点或null。                        setHead(node);                        p.next = null; // help GC 这里帮助垃圾回收器回收节点                        failed = false;//返回等待过程中是否被中断过                        return interrupted;                    }                    // //如果自己可以休息了，就进入waiting状态，直到被unpark()                    /**                     * 结点进入队尾后，检查状态，找到安全休息点；                     调用park()进入waiting状态，等待unpark()或interrupt()唤醒自己；                     被唤醒后，看自己是不是有资格能拿到号。如果拿到，head指向当前结点，                     并返回从入队到拿到号的整个过程中是否被中断过；如果没拿到，继续流程1。                     */                    if (shouldParkAfterFailedAcquire(p, node) &&                            parkAndCheckInterrupt())//检查状态 接下来将会进行检查状态分析 看看线程是否进入waiting状态                        interrupted = true;////如果等待过程中被中断过，哪怕只有那么一次，就将interrupted标记为true                }            } finally {                if (failed)                    cancelAcquire(node);            }        }        private void doAcquireInterruptibly(int arg)                throws InterruptedException {            final Node node = addWaiter(Node.EXCLUSIVE);            boolean failed = true;            try {                for (;;) {                    final Node p = node.predecessor();                    if (p == head && tryAcquire(arg)) {                        setHead(node);                        p.next = null; // help GC                        failed = false;                        return;                    }                    if (shouldParkAfterFailedAcquire(p, node) &&                            parkAndCheckInterrupt())                        throw new InterruptedException();                }            } finally {                if (failed)                    cancelAcquire(node);            }        }        private boolean doAcquireNanos(int arg, long nanosTimeout)                throws InterruptedException {            if (nanosTimeout <= 0L)                return false;            final long deadline = System.nanoTime() + nanosTimeout;            final Node node = addWaiter(Node.EXCLUSIVE);            boolean failed = true;            try {                for (;;) {                    final Node p = node.predecessor();                    if (p == head && tryAcquire(arg)) {                        setHead(node);                        p.next = null; // help GC                        failed = false;                        return true;                    }                    nanosTimeout = deadline - System.nanoTime();                    if (nanosTimeout <= 0L)                        return false;                    if (shouldParkAfterFailedAcquire(p, node) &&                            nanosTimeout > spinForTimeoutThreshold)                        LockSupport.parkNanos(this, nanosTimeout);                    if (Thread.interrupted())                        throw new InterruptedException();                }            } finally {                if (failed)                    cancelAcquire(node);            }        }    /**     * 此方法用于将当前线程加入等待队列尾部休息，直到其他线程释放资源唤醒自己，     * 自己成功拿到相应量的资源后才返回。下面是doAcquireShared()的源码：　　     * 有木有觉得跟acquireQueued()很相似？对，其实流程并没有太大区别。     * 只不过这里将补中断的selfInterrupt()放到doAcquireShared()里了，     * 而独占模式是放到acquireQueued()之外，其实都一样.　跟独占模式比，     * 还有一点需要注意的是，这里只有线程是head.next时（“老二”），     * 才会去尝试获取资源，有剩余的话还会唤醒之后的队友。那么问题就来了，     * 假如老大用完后释放了5个资源，而老二需要6个，老三需要1个，老四需要2个。     * 因为老大先唤醒老二，老二一看资源不够自己用继续park()，也更不会去唤醒老三和老四了。     * 独占模式，同一时刻只有一个线程去执行，这样做未尝不可；但共享模式下，     * 多个线程是可以同时执行的，现在因为老二的资源需求量大，     * 而把后面量小的老三和老四也都卡住了。     * @param arg     */        private void doAcquireShared(int arg) {            final Node node = addWaiter(Node.SHARED);//加入队列尾部            boolean failed = true;//是否成功标志            try {                boolean interrupted = false;//等待过程中是否被中断过的标志                for (;;) {                    final Node p = node.predecessor();//前驱                    if (p == head) {                        int r = tryAcquireShared(arg);//如果到head的下一个，因为head是拿到资源的线程，此时node被唤醒，                        // 很可能是head用完资源来唤醒自己的,尝试获取资源                        if (r >= 0) {                            setHeadAndPropagate(node, r);//将head指向自己，还有剩余资源可以再唤醒之后的线程                            p.next = null; // help GC                            if (interrupted)                                selfInterrupt();//如果等待过程中被打断过，此时将中断补上。                            failed = false;                            return;                        }                    }                    //判断状态，寻找安全点，进入waiting状态，等着被unpark()或interrupt()                    if (shouldParkAfterFailedAcquire(p, node) &&                            parkAndCheckInterrupt())                        interrupted = true;                }            } finally {                if (failed)                    cancelAcquire(node);            }        }        private void doAcquireSharedInterruptibly(int arg)                throws InterruptedException {            final Node node = addWaiter(Node.SHARED);            boolean failed = true;            try {                for (;;) {                    final Node p = node.predecessor();                    if (p == head) {                        int r = tryAcquireShared(arg);                        if (r >= 0) {                            setHeadAndPropagate(node, r);                            p.next = null; // help GC                            failed = false;                            return;                        }                    }                    if (shouldParkAfterFailedAcquire(p, node) &&                            parkAndCheckInterrupt())                        throw new InterruptedException();                }            } finally {                if (failed)                    cancelAcquire(node);            }        }        private boolean doAcquireSharedNanos(int arg, long nanosTimeout)                throws InterruptedException {            if (nanosTimeout <= 0L)                return false;            final long deadline = System.nanoTime() + nanosTimeout;            final Node node = addWaiter(Node.SHARED);            boolean failed = true;            try {                for (;;) {                    final Node p = node.predecessor();                    if (p == head) {                        int r = tryAcquireShared(arg);                        if (r >= 0) {                            setHeadAndPropagate(node, r);                            p.next = null; // help GC                            failed = false;                            return true;                        }                    }                    nanosTimeout = deadline - System.nanoTime();                    if (nanosTimeout <= 0L)                        return false;                    if (shouldParkAfterFailedAcquire(p, node) &&                            nanosTimeout > spinForTimeoutThreshold)                        LockSupport.parkNanos(this, nanosTimeout);                    if (Thread.interrupted())                        throw new InterruptedException();                }            } finally {                if (failed)                    cancelAcquire(node);            }        }    /**     * tryAcquire()尝试直接去获取资源，如果成功则直接返回；     * 此方法尝试去获取独占资源。如果获取成功，则直接返回true，否则直接返回false。     * 这也正是tryLock()的语义，当然不仅仅只限于tryLock()。如下是tryAcquire()的源码：     * 至于为甚这里直接抛出异常因为AQS只是一个框架，具体资源的获取/释放方式交由自定义同步器去实现，之所以没有抽象是因为     * 只是抢占锁 该框架还有共享锁的定义 所以写成抽象不方便开发者书写。     * @param arg     * @return     */        protected boolean tryAcquire(int arg) {            throw new UnsupportedOperationException();        }    /**     *     * @param arg     * @return     * 跟tryAcquire()一样，这个方法是需要独占模式的自定义同步器去实现的。正常来说，tryRelease()都会成功的，因为这是独占模式，该线程来释放资源，那么它肯定已经拿到独占资源了，直接减掉相应量的资源即可(state-=arg)，也不需要考虑线程安全的问题。但要注意它的返回值，上面已经提到了，release()是根据tryRelease()的返回值来判断该线程是否已经完成释放掉资源了！所以自义定同步器在实现时，     * 如果已经彻底释放资源(state=0)，要返回true，否则返回false  和上面的设计理念一样     * 这个函数并不复杂。一句话概括：用unpark()唤醒等待队列中最前边的那个未放弃线程，这里我们也用s来表示吧。此时，再和acquireQueued()联系起来，s被唤醒后，进入if (p == head && tryAcquire(arg))的判断（即使p!=head也没关系，它会再进入shouldParkAfterFailedAcquire()寻找一个安全点。这里既然s已经是等待队列中最前边的那个未放弃线程了，那么通过shouldParkAfterFailedAcquire()的调整，s也必然会跑到head的next结点，下一次自旋p==head就成立啦），然后s把自己设置成head标杆结点，表示自己已经获取到资源了，     * acquire()也返回了！！release()是独占模式下线程释放共享资源的顶层入口。它会释放指定量的资源，如果彻底释放了（即state=0）,它会唤醒等待队列里的其他线程来获取资源。     */        protected boolean tryRelease(int arg) {            throw new UnsupportedOperationException();        }    /**     * @param arg     * @return     */        protected int tryAcquireShared(int arg) {            throw new UnsupportedOperationException();        }        protected boolean tryReleaseShared(int arg) {            throw new UnsupportedOperationException();        }        protected boolean isHeldExclusively() {            throw new UnsupportedOperationException();        }    /**     * 此方法是独占模式下线程获取共享资源的顶层入口。如果获取到资源，线程直接返回，否则进入等待队列，直到获取到资源为止，且整个过程忽略中断的影响。这也正是lock()的语义，     * 当然不仅仅只限于lock()。获取到资源后，线程就可以去执行其临界区代码了.调用自定义同步器的tryAcquire()尝试直接去获取资源，如果成功则直接返回；     没成功，则addWaiter()将该线程加入等待队列的尾部，并标记为独占模式；acquireQueued()使线程在等待队列中休息，有机会时（轮到自己，会被unpark()）会去尝试获取资源。获取到资源后才返回。如果在整个等待过程中被中断过，则返回true，否则返回false。     如果线程在等待过程中被中断过，它是不响应的。只是获取资源后才再进行自我中断selfInterrupt()，将中断补上。     * @param arg     */        public final void acquire(int arg) {            if (!tryAcquire(arg) &&                    acquireQueued(addWaiter(Node.EXCLUSIVE), arg))                selfInterrupt();        }        public final void acquireInterruptibly(int arg)                throws InterruptedException {            if (Thread.interrupted())                throw new InterruptedException();            if (!tryAcquire(arg))                doAcquireInterruptibly(arg);        }        public final boolean tryAcquireNanos(int arg, long nanosTimeout)                throws InterruptedException {            if (Thread.interrupted())                throw new InterruptedException();            return tryAcquire(arg) ||                    doAcquireNanos(arg, nanosTimeout);        }    /**     * 释放     * @param arg     * @return     */        public final boolean release(int arg) {            if (tryRelease(arg)) {//它调用tryRelease()来释放资源。有一点需要注意的是，它是根据tryRelease()的返回值来判断该线程是否已经完成释放掉资源了！所以自定义同步器在设计tryRelease()的时候要明确这一点！！                Node h = head;//找到头结点                if (h != null && h.waitStatus != 0)                    unparkSuccessor(h);//唤醒等待队列里的下一个线程                return true;            }            return false;        }    /**     * 此方法是共享模式下线程获取共享资源的顶层入口。它会获取指定量的资源，获取成功则直接返回，获取失败则进入等待队列，     * 直到获取到资源为止，整个过程忽略中断。下面是acquireShared()的源码：tryAcquireShared()尝试获取资源，成功则直接返回；     失败则通过doAcquireShared()进入等待队列park()，直到被unpark()/interrupt()并成功获取到资源才返回。整个等待过程也是忽略中断的。     其实跟acquire()的流程大同小异，只不过多了个自己拿到资源后，还会去唤醒后继队友的操作（这才是共享嘛）。     * @param arg     */        public final void acquireShared(int arg) {            /**             * 这里tryAcquireShared()依然需要自定义同步器去实现。但是AQS已经把其返回值的语义定义好了：             * 负值代表获取失败；0代表获取成功，但没有剩余资源；正数表示获取成功，还有剩余资源，其他线程还可以去获取。             * 所以这里acquireShared()的流程就是：tryAcquireShared()尝试获取资源，成功则直接返回；              失败则通过doAcquireShared()进入等待队列，直到获取到资源为止才返回。             */            if (tryAcquireShared(arg) < 0)                doAcquireShared(arg);        }        public final void acquireSharedInterruptibly(int arg)                throws InterruptedException {            if (Thread.interrupted())                throw new InterruptedException();            if (tryAcquireShared(arg) < 0)                doAcquireSharedInterruptibly(arg);        }        public final boolean tryAcquireSharedNanos(int arg, long nanosTimeout)                throws InterruptedException {            if (Thread.interrupted())                throw new InterruptedException();            return tryAcquireShared(arg) >= 0 ||                    doAcquireSharedNanos(arg, nanosTimeout);        }    /**     * releaseShared()吧。此方法是共享模式下线程释放共享资源的顶层入口。它会释放指定量的资源，     * 如果彻底释放了（即state=0）,它会唤醒等待队列里的其他线程来获取资源。下面是releaseShared()的源码：     * 释放掉资源后，唤醒后继。跟独占模式下的release()相似，但有一点稍微需要注意：     * 独占模式下的tryRelease()在完全释放掉资源（state=0）后，才会返回true去唤醒其他线程，     * 这主要是基于可重入的考量；而共享模式下的releaseShared()则没有这种要求，     * 一是共享的实质--多线程可并发执行；二是共享模式基本也不会重入，     * 所以自定义同步器可以根据需要决定返回值。     * @param arg     * @return     */        public final boolean releaseShared(int arg) {            if (tryReleaseShared(arg)) {//尝试释放资源                doReleaseShared();//唤醒后继结点                return true;            }            return false;        }        public final boolean hasQueuedThreads() {            return head != tail;        }        public final boolean hasContended() {            return head != null;        }        public final Thread getFirstQueuedThread() {            return (head == tail) ? null : fullGetFirstQueuedThread();        }        private Thread fullGetFirstQueuedThread() {            Node h, s;            Thread st;            if (((h = head) != null && (s = h.next) != null &&                    s.prev == head && (st = s.thread) != null) ||                    ((h = head) != null && (s = h.next) != null &&                            s.prev == head && (st = s.thread) != null))                return st;            Node t = tail;            Thread firstThread = null;            while (t != null && t != head) {                Thread tt = t.thread;                if (tt != null)                    firstThread = tt;                t = t.prev;            }            return firstThread;        }        public final boolean isQueued(Thread thread) {            if (thread == null)                throw new NullPointerException();            for (Node p = tail; p != null; p = p.prev)                if (p.thread == thread)                    return true;            return false;        }        final boolean apparentlyFirstQueuedIsExclusive() {            Node h, s;            return (h = head) != null &&                    (s = h.next)  != null &&                    !s.isShared()         &&                    s.thread != null;        }        public final boolean hasQueuedPredecessors() {            Node t = tail; // Read fields in reverse initialization order            Node h = head;            Node s;            return h != t &&                    ((s = h.next) == null || s.thread != Thread.currentThread());        }        public final int getQueueLength() {            int n = 0;            for (Node p = tail; p != null; p = p.prev) {                if (p.thread != null)                    ++n;            }            return n;        }        public final Collection<Thread> getQueuedThreads() {            ArrayList<Thread> list = new ArrayList<Thread>();            for (Node p = tail; p != null; p = p.prev) {                Thread t = p.thread;                if (t != null)                    list.add(t);            }            return list;        }        public final Collection<Thread> getExclusiveQueuedThreads() {            ArrayList<Thread> list = new ArrayList<Thread>();            for (Node p = tail; p != null; p = p.prev) {                if (!p.isShared()) {                    Thread t = p.thread;                    if (t != null)                        list.add(t);                }            }            return list;        }        public final Collection<Thread> getSharedQueuedThreads() {            ArrayList<Thread> list = new ArrayList<Thread>();            for (Node p = tail; p != null; p = p.prev) {                if (p.isShared()) {                    Thread t = p.thread;                    if (t != null)                        list.add(t);                }            }            return list;        }        public String toString() {            int s = getState();            String q  = hasQueuedThreads() ? "non" : "";            return super.toString() +                    "[State = " + s + ", " + q + "empty queue]";        }        final boolean isOnSyncQueue(Node node) {            if (node.waitStatus == Node.CONDITION || node.prev == null)                return false;            if (node.next != null) // If has successor, it must be on queue                return true;            return findNodeFromTail(node);        }        private boolean findNodeFromTail(Node node) {            Node t = tail;            for (;;) {                if (t == node)                    return true;                if (t == null)                    return false;                t = t.prev;            }        }        final boolean transferForSignal(Node node) {            if (!compareAndSetWaitStatus(node, Node.CONDITION, 0))                return false;            Node p = enq(node);            int ws = p.waitStatus;            if (ws > 0 || !compareAndSetWaitStatus(p, ws, Node.SIGNAL))                LockSupport.unpark(node.thread);            return true;        }        final boolean transferAfterCancelledWait(Node node) {            if (compareAndSetWaitStatus(node, Node.CONDITION, 0)) {                enq(node);                return true;}            while (!isOnSyncQueue(node))                Thread.yield();            return false;        }         final int fullyRelease(Node node) {            boolean failed = true;            try {                int savedState = getState();                if (release(savedState)) {                    failed = false;                    return savedState;                } else {                    throw new IllegalMonitorStateException();                }            } finally {                if (failed)                    node.waitStatus = Node.CANCELLED;            }        }        public final boolean owns(ConditionObject condition) {            return condition.isOwnedBy(this);        }        public final boolean hasWaiters(ConditionObject condition) {            if (!owns(condition))                throw new IllegalArgumentException("Not owner");            return condition.hasWaiters();        }        public final int getWaitQueueLength(ConditionObject condition) {            if (!owns(condition))                throw new IllegalArgumentException("Not owner");            return condition.getWaitQueueLength();        }        public final Collection<Thread> getWaitingThreads(ConditionObject condition) {            if (!owns(condition))                throw new IllegalArgumentException("Not owner");            return condition.getWaitingThreads();        }        public class ConditionObject implements Condition, java.io.Serializable {            private static final long serialVersionUID = 1173984872572414699L;            /** First node of condition queue. */            private transient Node firstWaiter;            /** Last node of condition queue. */            private transient Node lastWaiter;            public ConditionObject() { }            private Node addConditionWaiter() {                Node t = lastWaiter;                // If lastWaiter is cancelled, clean out.                if (t != null && t.waitStatus != Node.CONDITION) {                    unlinkCancelledWaiters();                    t = lastWaiter;                }                Node node = new Node(Thread.currentThread(), Node.CONDITION);                if (t == null)                    firstWaiter = node;                else                    t.nextWaiter = node;                lastWaiter = node;                return node;            }            private void doSignal(Node first) {                do {                    if ( (firstWaiter = first.nextWaiter) == null)                        lastWaiter = null;                    first.nextWaiter = null;                } while (!transferForSignal(first) &&                        (first = firstWaiter) != null);            }            private void doSignalAll(Node first) {                lastWaiter = firstWaiter = null;                do {                    Node next = first.nextWaiter;                    first.nextWaiter = null;                    transferForSignal(first);                    first = next;                } while (first != null);            }            private void unlinkCancelledWaiters() {                Node t = firstWaiter;                Node trail = null;                while (t != null) {                    Node next = t.nextWaiter;                    if (t.waitStatus != Node.CONDITION) {                        t.nextWaiter = null;                        if (trail == null)                            firstWaiter = next;                        else                            trail.nextWaiter = next;                        if (next == null)                            lastWaiter = trail;                    }                    else                        trail = t;                    t = next;                }            }            public final void signal() {                if (!isHeldExclusively())                    throw new IllegalMonitorStateException();                Node first = firstWaiter;                if (first != null)                    doSignal(first);            }            public final void signalAll() {                if (!isHeldExclusively())                    throw new IllegalMonitorStateException();                Node first = firstWaiter;                if (first != null)                    doSignalAll(first);            }            public final void awaitUninterruptibly() {                Node node = addConditionWaiter();                int savedState = fullyRelease(node);                boolean interrupted = false;                while (!isOnSyncQueue(node)) {                    LockSupport.park(this);                    if (Thread.interrupted())                        interrupted = true;                }                if (acquireQueued(node, savedState) || interrupted)                    selfInterrupt();            }            private static final int REINTERRUPT =  1;            private static final int THROW_IE    = -1;            private int checkInterruptWhileWaiting(Node node) {                return Thread.interrupted() ?                        (transferAfterCancelledWait(node) ? THROW_IE : REINTERRUPT) :                        0;            }            private void reportInterruptAfterWait(int interruptMode)                    throws InterruptedException {                if (interruptMode == THROW_IE)                    throw new InterruptedException();                else if (interruptMode == REINTERRUPT)                    selfInterrupt();            }            public final void await() throws InterruptedException {                if (Thread.interrupted())                    throw new InterruptedException();                Node node = addConditionWaiter();                int savedState = fullyRelease(node);                int interruptMode = 0;                while (!isOnSyncQueue(node)) {                    LockSupport.park(this);                    if ((interruptMode = checkInterruptWhileWaiting(node)) != 0)                        break;                }                if (acquireQueued(node, savedState) && interruptMode != THROW_IE)                    interruptMode = REINTERRUPT;                if (node.nextWaiter != null) // clean up if cancelled                    unlinkCancelledWaiters();                if (interruptMode != 0)                    reportInterruptAfterWait(interruptMode);            }            public final long awaitNanos(long nanosTimeout)                    throws InterruptedException {                if (Thread.interrupted())                    throw new InterruptedException();                Node node = addConditionWaiter();                int savedState = fullyRelease(node);                final long deadline = System.nanoTime() + nanosTimeout;                int interruptMode = 0;                while (!isOnSyncQueue(node)) {                    if (nanosTimeout <= 0L) {                        transferAfterCancelledWait(node);                        break;                    }                    if (nanosTimeout >= spinForTimeoutThreshold)                        LockSupport.parkNanos(this, nanosTimeout);                    if ((interruptMode = checkInterruptWhileWaiting(node)) != 0)                        break;                    nanosTimeout = deadline - System.nanoTime();                }                if (acquireQueued(node, savedState) && interruptMode != THROW_IE)                    interruptMode = REINTERRUPT;                if (node.nextWaiter != null)                    unlinkCancelledWaiters();                if (interruptMode != 0)                    reportInterruptAfterWait(interruptMode);                return deadline - System.nanoTime();            }            public final boolean awaitUntil(Date deadline)                    throws InterruptedException {                long abstime = deadline.getTime();                if (Thread.interrupted())                    throw new InterruptedException();                Node node = addConditionWaiter();                int savedState = fullyRelease(node);                boolean timedout = false;                int interruptMode = 0;                while (!isOnSyncQueue(node)) {                    if (System.currentTimeMillis() > abstime) {                        timedout = transferAfterCancelledWait(node);                        break;                    }                    LockSupport.parkUntil(this, abstime);                    if ((interruptMode = checkInterruptWhileWaiting(node)) != 0)                        break;                }                if (acquireQueued(node, savedState) && interruptMode != THROW_IE)                    interruptMode = REINTERRUPT;                if (node.nextWaiter != null)                    unlinkCancelledWaiters();                if (interruptMode != 0)                    reportInterruptAfterWait(interruptMode);                return !timedout;            }            public final boolean await(long time, TimeUnit unit)                    throws InterruptedException {                long nanosTimeout = unit.toNanos(time);                if (Thread.interrupted())                    throw new InterruptedException();                Node node = addConditionWaiter();                int savedState = fullyRelease(node);                final long deadline = System.nanoTime() + nanosTimeout;                boolean timedout = false;                int interruptMode = 0;                while (!isOnSyncQueue(node)) {                    if (nanosTimeout <= 0L) {                        timedout = transferAfterCancelledWait(node);                        break;                    }                    if (nanosTimeout >= spinForTimeoutThreshold)                        LockSupport.parkNanos(this, nanosTimeout);                    if ((interruptMode = checkInterruptWhileWaiting(node)) != 0)                        break;                    nanosTimeout = deadline - System.nanoTime();                }                if (acquireQueued(node, savedState) && interruptMode != THROW_IE)                    interruptMode = REINTERRUPT;                if (node.nextWaiter != null)                    unlinkCancelledWaiters();                if (interruptMode != 0)                    reportInterruptAfterWait(interruptMode);                return !timedout;            }            final boolean isOwnedBy(AbstractQueuedSynchronizer sync) {                return sync == AbstractQueuedSynchronizer.this;            }            protected final boolean hasWaiters() {                if (!isHeldExclusively())                    throw new IllegalMonitorStateException();                for (Node w = firstWaiter; w != null; w = w.nextWaiter) {                    if (w.waitStatus == Node.CONDITION)                        return true;                }                return false;            }            protected final int getWaitQueueLength() {                if (!isHeldExclusively())                    throw new IllegalMonitorStateException();                int n = 0;                for (Node w = firstWaiter; w != null; w = w.nextWaiter) {                    if (w.waitStatus == Node.CONDITION)                        ++n;                }                return n;            }            protected final Collection<Thread> getWaitingThreads() {                if (!isHeldExclusively())                    throw new IllegalMonitorStateException();                ArrayList<Thread> list = new ArrayList<Thread>();                for (Node w = firstWaiter; w != null; w = w.nextWaiter) {                    if (w.waitStatus == Node.CONDITION) {                        Thread t = w.thread;                        if (t != null)                            list.add(t);                    }                }                return list;            }        }        private static final Unsafe unsafe = Unsafe.getUnsafe();        private static final long stateOffset;        private static final long headOffset;        private static final long tailOffset;        private static final long waitStatusOffset;        private static final long nextOffset;        static {            try {                /**                 * 利用静态代码块  实现得到对象的偏移量 那么就可一利用cas机制了                 */                stateOffset = unsafe.objectFieldOffset                        (AbstractQueuedSynchronizer.class.getDeclaredField("state"));                headOffset = unsafe.objectFieldOffset                        (AbstractQueuedSynchronizer.class.getDeclaredField("head"));                tailOffset = unsafe.objectFieldOffset                        (AbstractQueuedSynchronizer.class.getDeclaredField("tail"));                waitStatusOffset = unsafe.objectFieldOffset                        (Node.class.getDeclaredField("waitStatus"));                nextOffset = unsafe.objectFieldOffset                        (Node.class.getDeclaredField("next"));            } catch (Exception ex) { throw new Error(ex); }        }        private final boolean compareAndSetHead(Node update) {            return unsafe.compareAndSwapObject(this, headOffset, null, update);        }        private final boolean compareAndSetTail(Node expect, Node update) {            return unsafe.compareAndSwapObject(this, tailOffset, expect, update);        }        private static final boolean compareAndSetWaitStatus(Node node,                                                             int expect,                                                             int update) {            return unsafe.compareAndSwapInt(node, waitStatusOffset,                    expect, update);        }        private static final boolean compareAndSetNext(Node node,                                                       Node expect,                                                       Node update) {            return unsafe.compareAndSwapObject(node, nextOffset, expect, update);        }    }

package com.kailong.lock;/** * Created by Administrator on 2017/4/20. */public class AbstractOwnableSynchronizer implements java.io.Serializable {    /** 序列化id */    private static final long serialVersionUID = 3737899427754241961L;    /**     * 空构造器供子类使用。     */    protected AbstractOwnableSynchronizer() { }    /**     * 当前所有者的排他模式同步。     */    private transient Thread exclusiveOwnerThread;    /**     * 设置当前拥有独占访问权限的线程。      {@code null}参数表示没有线程拥有访问权限。      这种方法不会强加任何同步或      {@code volatile}字段访问。      @param线程所有者线程     */    protected final void setExclusiveOwnerThread(Thread thread) {        exclusiveOwnerThread = thread;    }    /**     *返回由{@code setExclusiveOwnerThread}最后设置的线程，     *或{@code null}如果从未设置。 此方法不另行     *强制执行任何同步或{@code易失性}字段访问。     *返回所有者线程     */    protected final Thread getExclusiveOwnerThread() {        return exclusiveOwnerThread;    }}

package com.kailong.lock;import java.util.Collection;import java.util.concurrent.TimeUnit;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;import java.util.concurrent.locks.ReentrantReadWriteLock;/** * Created by Administrator on 2017/4/20. */public class MyLock {    private final Sync sync;//同步策略    /**     * 抽象的同步  用模板方法设计模式  提供两种策略 公平锁和非公平锁     */    static abstract class Sync extends AbstractQueuedSynchronizer{        private static final long serialVersionUID = -5179523762034025860L;        abstract void lock();//抽象加锁方法        /**         *  这个方法相当于AQS的ryAcquire，为什么非公平版的TryAcquire代码需要写在父类Sync 这里？          注意tryLock，它是只调用非公平版的tryLock。而ReentrantLock 是代理了          Sync ，根据多态机制。所以非公平版的TryAcquire只能写在父类Sync这里了。         * @param acquires         * @return         */        final boolean nonfairTryAcquire(int acquires) {            final Thread current = Thread.currentThread();            int c = getState();            if (c == 0) {                if (compareAndSetState(0, acquires)) {                    setExclusiveOwnerThread(current);                    return true;                }            }            else if (current == getExclusiveOwnerThread()) {                int nextc = c + acquires;                if (nextc < 0) // overflow                    throw new Error("Maximum lock count exceeded");                setState(nextc);                return true;            }            return false;        }        protected final boolean tryRelease(int releases) {            int c = getState() - releases;            if (Thread.currentThread() != getExclusiveOwnerThread())                throw new IllegalMonitorStateException();            boolean free = false;            if (c == 0) {                free = true;                setExclusiveOwnerThread(null);            }            setState(c);            return free;        }        protected final boolean isHeldExclusively() {            return getExclusiveOwnerThread() == Thread.currentThread();        }        final ConditionObject newCondition() {            return new ConditionObject();        }        final Thread getOwner() {            return getState() == 0 ? null : getExclusiveOwnerThread();        }        final int getHoldCount() {            return isHeldExclusively() ? getState() : 0;        }        final boolean isLocked() {            return getState() != 0;        }        private void readObject(java.io.ObjectInputStream s)                throws java.io.IOException, ClassNotFoundException {            s.defaultReadObject();            setState(0); // reset to unlocked state        }    }    /**     * 静态内部类  实现非公平锁     */    static  final  class  NonfairSync extends Sync{        @Override        void lock() {            if (compareAndSetState(0, 1))                setExclusiveOwnerThread(Thread.currentThread());            else                acquire(1);        }        protected final boolean tryAcquire(int acquires) {            return nonfairTryAcquire(acquires);        }    }    /**     * 静态内部类实现公平锁     */    static final class FairSync extends Sync{        @Override        void lock() {            acquire(1);        }        protected final boolean tryAcquire(int acquires) {            final Thread current = Thread.currentThread();            int c = getState();            if (c == 0) {                if (!hasQueuedPredecessors() &&                        compareAndSetState(0, acquires)) {                    setExclusiveOwnerThread(current);                    return true;                }            }            else if (current == getExclusiveOwnerThread()) {                int nextc = c + acquires;                if (nextc < 0)                    throw new Error("Maximum lock count exceeded");                setState(nextc);                return true;            }            return false;        }    }    /**     * 无参构造方法默认是非公平锁     */    public MyLock() {        sync = new NonfairSync();    }    /**     * 传递boolean值 判断公平锁还是非公平锁     * @param fair     */    public MyLock(boolean fair) {        sync = fair ? new FairSync() : new NonfairSync();    }    /**     * 加锁方法 调用sync的lock方法 他会根据子类的模板方法来加锁 实现公平锁或者非公平锁     */    public void lock() {        sync.lock();    }    /**     *     * @throws InterruptedException     */    public void lockInterruptibly() throws InterruptedException {        sync.acquireInterruptibly(1);    }    /**     *     * @return     */    public boolean tryLock() {        return sync.nonfairTryAcquire(1);    }    /**     *     * @param timeout     * @param unit     * @return     * @throws InterruptedException     */    public boolean tryLock(long timeout, TimeUnit unit)            throws InterruptedException {        return sync.tryAcquireNanos(1, unit.toNanos(timeout));    }    /**     *     */    public void unlock() {        sync.release(1);    }    /**     *     * @return     */    public Condition newCondition() {        return sync.newCondition();    }    /**     *     * @return     */    public int getHoldCount() {        return sync.getHoldCount();    }    /**     *     * @return     */    public boolean isHeldByCurrentThread() {        return sync.isHeldExclusively();    }    /**     *     * @return     */    public boolean isLocked() {        return sync.isLocked();    }    /**     *     * @return     */    public final boolean isFair() {        return sync instanceof FairSync;    }    /**     *     * @return     */    protected Thread getOwner() {        return sync.getOwner();    }    /**     *     * @return     */    public final boolean hasQueuedThreads() {        return sync.hasQueuedThreads();    }    /**     *     * @param thread     * @return     */    public final boolean hasQueuedThread(Thread thread) {        return sync.isQueued(thread);    }    /**     *     * @return     */    public final int getQueueLength() {        return sync.getQueueLength();    }    /**     *     * @return     */    protected Collection<Thread> getQueuedThreads() {        return sync.getQueuedThreads();    }    /**     *     * @param condition     * @return     */    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);    }    /**     *     * @param condition     * @return     */    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);    }    /**     *     * @param condition     * @return     */    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);    }    /**     * toString 方法覆盖     * @return     */    public String toString() {        Thread o = sync.getOwner();        return super.toString() + ((o == null) ?                "[Unlocked]" :                "[Locked by thread " + o.getName() + "]");    }    public  static void main(String[]args){        Lock lock=new ReentrantLock();    }}

package com.kailong.lock;import java.util.concurrent.TimeUnit;import java.util.concurrent.locks.Condition;/** * Created by Administrator on 2017/4/20. * 自定义顶层接口 实现锁的基本功能 */public interface MysLock {    /**     * 加锁  如果锁已经被占用那么等待     */    void lock();    /**     *获得锁但优先响应中断     * @throws InterruptedException     */    void lockInterruptibly() throws InterruptedException;    /**     * 尝试获得锁 如果成功 返回true 失败返回false 此方法不等待，立即返回     * @return     */    boolean tryLock();    /**     *给定时间尝试获得锁     * @param time     * @param unit     * @return     * @throws InterruptedException     */    boolean tryLock(long time, TimeUnit unit) throws InterruptedException;    /**     * 释放锁     */    void unlock();    /**     *条件     * @return     */    Condition newCondition();}