package com.example.demo.study;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

public class Study0201 {

    public static void main(String[] args) throws InterruptedException {
        // 創(chuàng)建鎖對(duì)象
        ReentrantLock lock = new ReentrantLock();
        // 創(chuàng)建條件變量
        Condition condition = lock.newCondition();
        // 以下創(chuàng)建兩個(gè)線程，里面都會(huì)獲取鎖和釋放鎖
        Thread thread1 = new Thread(() -> {
            lock.lock();
            try {
                System.out.println("await begin");
                // 注意，這里調(diào)用條件變量的await方法，當(dāng)前線程就會(huì)丟到condition條件變量中的條件隊(duì)列中阻塞
                condition.await();
                System.out.println("await end");
            } catch (InterruptedException e) {
                //
            } finally {
                lock.unlock();
            }

        });

        Thread thread2 = new Thread(() -> {
            lock.lock();
            try {
                System.out.println("signal begin");
                // 喚醒被condition變量?jī)?nèi)部隊(duì)列中的某個(gè)線程
                condition.signal();
                System.out.println("signal end");
            } finally {
                lock.unlock();
            }
        });
        thread1.start();
        Thread.sleep(500);
        thread2.start();
    }
}

package com.example.demo.study;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

public class Study0201 {

    public static void main(String[] args) throws InterruptedException {
        // 創(chuàng)建鎖對(duì)象
        ReentrantLock lock = new ReentrantLock();
        // 創(chuàng)建條件變量1
        Condition condition1 = lock.newCondition();
        //條件變量2
        Condition condition2 = lock.newCondition();
        
        // 以下創(chuàng)建兩個(gè)線程，里面都會(huì)獲取鎖和釋放鎖
        Thread thread1 = new Thread(() -> {
            lock.lock();
            try {
                System.out.println("await begin");//1
                condition1.await();
                System.out.println("await end");//5
                
                System.out.println("condition2---signal---start");//6
                condition2.signal();
                System.out.println("condition2---signal---endend");//7
            } catch (InterruptedException e) {
                //
            } finally {
                lock.unlock();
            }

        });

        Thread thread2 = new Thread(() -> {

            lock.lock();
            try {
                System.out.println("signal begin");//2
                condition1.signal();
                System.out.println("signal end");//3
                
                System.out.println("condition2---await---start");//4
                condition2.await();
                System.out.println("condition2---await---end");//8
            } catch (InterruptedException e) {
                //
            } finally {
                lock.unlock();
            }

        });

        thread1.start();
        Thread.sleep(500);
        thread2.start();

    }

}

public final void await() throws InterruptedException {
    if (Thread.interrupted())
        throw new InterruptedException();
    //新建一個(gè)Node.CONDITION節(jié)點(diǎn)放到條件隊(duì)列最后面
    Node node = addConditionWaiter();
    //釋放當(dāng)前線程獲取的鎖
    int savedState = fullyRelease(node);
    int interruptMode = 0;
    //調(diào)用park()方法阻塞掛起當(dāng)前線程
    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);
}

private Node addConditionWaiter() {
    Node t = lastWaiter;
    //第一次進(jìn)來(lái)，這個(gè)lastWaiter是null，即t = null,不會(huì)進(jìn)入到這個(gè)if語(yǔ)句
    if (t != null && t.waitStatus != Node.CONDITION) {
        unlinkCancelledWaiters();
        t = lastWaiter;
    }
    //創(chuàng)建一個(gè)Node.CONDITION類型的節(jié)點(diǎn)，然后下面這個(gè)if中就是將第一個(gè)節(jié)點(diǎn)firstWaiter和最后一個(gè)節(jié)點(diǎn)都指向這個(gè)新創(chuàng)建的節(jié)點(diǎn)
    Node node = new Node(Thread.currentThread(), Node.CONDITION);
    if (t == null)
        firstWaiter = node;
    else
        t.nextWaiter = node;
    lastWaiter = node;
    return node;
}

public final void signal() {
    if (!isHeldExclusively())
        throw new IllegalMonitorStateException();
    //條件隊(duì)列移除第一個(gè)節(jié)點(diǎn)，然后把這個(gè)節(jié)點(diǎn)丟到阻塞隊(duì)列中，然后激活這個(gè)線程
    Node first = firstWaiter;
    if (first != null)
        doSignal(first);
}