Java并發(fā)中的ReentrantLock和AQS的源碼詳解

public class ReentrantLockText {
		
	public static void main(String[] args) {
		Lock lock = new ReentrantLock();
		
		
		Thread t1 = new Thread(()->{
			try {
				lock.lock();
				System.out.println("t1 start");
				TimeUnit.SECONDS.sleep(Integer.MAX_VALUE);
				System.out.println("t1 end");
			} catch (InterruptedException e) {
				System.out.println("interrupted!");
			} finally {
				lock.unlock();
			}
		});
		t1.start();
		
		Thread t2 = new Thread(()->{
			try {
				//lock.lock();
				lock.lockInterruptibly(); //可以對interrupt()方法做出響應(yīng)
				System.out.println("t2 start");
				TimeUnit.SECONDS.sleep(5);
				System.out.println("t2 end");
			} catch (InterruptedException e) {
				System.out.println("interrupted!");
			} finally {
				lock.unlock();
			}
		});
		t2.start();
		
		try {
			TimeUnit.SECONDS.sleep(1);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		t2.interrupt(); //打斷線程2的等待
		
	}
}

public class Lock_condition {

    public static void main(String[] args) {

        char[] aI = "1234567".toCharArray();
        char[] aC = "ABCDEFG".toCharArray();

        Lock lock = new ReentrantLock();
        Condition conditionT1 = lock.newCondition();
        Condition conditionT2 = lock.newCondition();

        new Thread(()->{
            try {
                lock.lock();

                for(char c : aI) {
                    System.out.print(c);
                    conditionT2.signal();
                    conditionT1.await();
                }
                conditionT2.signal();

            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "t1").start();

        new Thread(()->{
            try {
                lock.lock();

                for(char c : aC) {
                    System.out.print(c);
                    conditionT1.signal();
                    conditionT2.await();
                }

                conditionT1.signal();

            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "t2").start();
    }
}

static final class Node {
        static final Node SHARED = new Node();
        static final Node EXCLUSIVE = null;
        static final int CANCELLED =  1;
        static final int SIGNAL    = -1;
        static final int PROPAGATE = -3;
        volatile int waitStatus;
        volatile Node next;
        volatile Node prev;
        volatile Thread thread;
        Node nextWaiter;

private transient volatile Node head;
    private transient volatile Node tail;
    private volatile int state;

ReentrantLock lock = new ReentrantLock(true);//ture則是公平鎖

final void lock() {
            if (compareAndSetState(0, 1))//cas原子操作嘗試去修改值，如果修改成功說明成功獲取到了鎖
                setExclusiveOwnerThread(Thread.currentThread());
            else
                acquire(1);
        }

protected final void setExclusiveOwnerThread(Thread thread) {
        exclusiveOwnerThread = thread;
    }

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;
        }

public final boolean hasQueuedPredecessors() {
        // The correctness of this depends on head being initialized
        // before tail and on head.next being accurate if the current
        // thread is first in queue.
        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 void acquire(int arg) {
        if (!tryAcquire(arg) &&
            acquireQueued(addWaiter(Node.EXCLUSIVE), arg))
            selfInterrupt();
    }

private Node addWaiter(Node mode) {
        Node node = new Node(Thread.currentThread(), mode);
        // Try the fast path of enq; backup to full enq on failure
        Node pred = tail;
        if (pred != null) {
            node.prev = pred;
            if (compareAndSetTail(pred, node)) {
                pred.next = node;
                return node;
            }
        }
        enq(node);
        return node;
    }

private Node enq(final Node node) {
        for (;;) {
            Node t = tail;
            if (t == null) { // Must initialize
                if (compareAndSetHead(new Node()))
                    tail = head;
            } else {
                node.prev = t;
                if (compareAndSetTail(t, node)) {
                    t.next = node;
                    return t;
                }
            }
        }
    }

final boolean acquireQueued(final Node node, int arg) {
        boolean failed = true;
        try {
            boolean interrupted = false;
            for (;;) {
                final Node p = node.predecessor();
                if (p == head && tryAcquire(arg)) {
                    setHead(node);
                    p.next = null; // help GC
                    failed = false;
                    return interrupted;
                }
                if (shouldParkAfterFailedAcquire(p, node) &&
                    parkAndCheckInterrupt())
                    interrupted = true;
            }
        } finally {
            if (failed)
                cancelAcquire(node);
        }
    }

private static boolean shouldParkAfterFailedAcquire(Node pred, Node node) {
        int ws = pred.waitStatus;
        if (ws == Node.SIGNAL)
            /*
             * This node has already set status asking a release
             * to signal it, so it can safely park.
             */
            return true;
        if (ws > 0) {
            /*
             * Predecessor was cancelled. Skip over predecessors and
             * indicate retry.
             */
            do {
                node.prev = pred = pred.prev;
            } while (pred.waitStatus > 0);
            pred.next = node;
        } else {
            /*
             * waitStatus must be 0 or PROPAGATE.  Indicate that we
             * need a signal, but don't park yet.  Caller will need to
             * retry to make sure it cannot acquire before parking.
             */
            compareAndSetWaitStatus(pred, ws, Node.SIGNAL);
        }
        return false;
    }

public final boolean release(int arg) {
        if (tryRelease(arg)) {
            Node h = head;
            if (h != null && h.waitStatus != 0)
                unparkSuccessor(h);
            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;
        }

final boolean acquireQueued(final Node node, int arg) {
        boolean failed = true;
        try {
            boolean interrupted = false;
            for (;;) {
            //被阻塞的線程，被喚醒后在進(jìn)行循環(huán)，
            //然后通過return interrupted;
                final Node p = node.predecessor();
                if (p == head && tryAcquire(arg)) {
                    setHead(node);
                    p.next = null; // help GC
                    failed = false;
                    return interrupted;
                }
                if (shouldParkAfterFailedAcquire(p, node) &&
                    parkAndCheckInterrupt())
                    interrupted = true;
            }
        } finally {
            if (failed)
                cancelAcquire(node);
        }
    }