一、让线程顺序运行的11种方法

1 方法说明

1. 使用线程的join方法
2. 使用主线程的join方法
3. 使用线程的wait方法
4. 使用线程的线程池方法
5. 使用线程的Condition（条件变量）方法
6. 使用CountDownLatch（倒计数）的方法
7. 使用线程的CyclicBarrier（回环栅栏）方法
8. 使用线程的Semaphore（信号量）方法
9. 使用LockSupport的park与unpark方法
10. 使用阻塞队列的put与take方法
11. 使用CAS思想来完成多线程的顺序执行AtomicReference<Thread>

2 实现

2.1 使用线程的join方法

**join()😗*是Theard的方法，作用是调用线程需等待该join()线程执行完成后，才能继续用下运行。

**应用场景：**当一个线程必须等待另一个线程执行完毕才能执行时可以使用join方法。

2.1.1 实现代码

package cn.lyf.leetcode.thread.demo;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.TimeUnit;

/**
 * @author lyf
 * @version 1.0
 * @classname ThreadDemo1
 * @description 方法说明
 *
 * 
 * 演示： 1、使用线程的join方法
 * join():是Theard的方法，作用是调用线程需等待该join()线程执行完成后，才能继续用下运行。
 * 
 * 应用场景：当一个线程必须等待另一个线程执行完毕才能执行时可以使用join方法。
 *
 * @since 2023/4/11 9:38
 */
@Slf4j
public class ThreadDemo1 {
    public static void main(String[] args) {
        Thread threadA = new Thread(() -> {
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
        }, "thread-a");

        Thread threadB = new Thread(() -> {
            try {
                threadA.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
        }, "thread-b");

        Thread threadC = new Thread(() -> {
            try {
                threadB.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
        }, "thread-c");

        threadA.start();
        threadB.start();
        threadC.start();
    }

    /**
     * 让线程睡眠timeOut 毫秒
     *
     * @param timeOut 单位毫秒
     */
    public static void sleep(long timeOut) {
        sleep(timeOut, TimeUnit.MILLISECONDS);
    }

    /**
     * 让线程睡眠
     *
     * @param timeOut 睡眠时间
     * @param unit    睡眠时间单位
     */
    public static void sleep(long timeOut, TimeUnit unit) {
        try {
            TimeUnit.MILLISECONDS.sleep(unit.toMillis(timeOut));
        } catch (InterruptedException e) {
            log.error("", e);
        }
    }
}

2.1.2 运行结果

2023-04-11 09:48:23 [ thread-a ]  INFO ThreadDemo1:39 - start...
2023-04-11 09:48:23 [ thread-a ]  INFO ThreadDemo1:42 - end...
2023-04-11 09:48:23 [ thread-b ]  INFO ThreadDemo1:51 - start...
2023-04-11 09:48:23 [ thread-b ]  INFO ThreadDemo1:54 - end...
2023-04-11 09:48:23 [ thread-c ]  INFO ThreadDemo1:63 - start...
2023-04-11 09:48:23 [ thread-c ]  INFO ThreadDemo1:66 - end...

2.2 使用主线程的join方法

在主线程中调用线程的join方法

2.2.1 实现代码

package cn.lyf.leetcode.thread.demo;

import lombok.extern.slf4j.Slf4j;

import static cn.lyf.leetcode.thread.demo.ThreadDemo1.sleep;

/**
 * @author lyf
 * @version 1.0
 * @classname ThreadDemo2
 * @description 方法说明
 *
 * 2. 使用主线程的join方法
 *
 * @since 2023/4/11 9:38
 */
@Slf4j
public class ThreadDemo2 {
    public static void main(String[] args) throws Exception {
        Thread threadA = new Thread(() -> {
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
        }, "thread-a");

        Thread threadB = new Thread(() -> {
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
        }, "thread-b");

        Thread threadC = new Thread(() -> {
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
        }, "thread-c");


        threadA.start();
        threadA.join();
        threadB.start();
        threadB.join();
        threadC.start();
    }
}

2.2.2 运行结果

2023-04-11 09:54:07 [ thread-a ]  INFO ThreadDemo2:36 - start...
2023-04-11 09:54:07 [ thread-a ]  INFO ThreadDemo2:39 - end...
2023-04-11 09:54:07 [ thread-b ]  INFO ThreadDemo2:43 - start...
2023-04-11 09:54:07 [ thread-b ]  INFO ThreadDemo2:46 - end...
2023-04-11 09:54:07 [ thread-c ]  INFO ThreadDemo2:50 - start...
2023-04-11 09:54:07 [ thread-c ]  INFO ThreadDemo2:53 - end...

2.3 使用线程的wait方法

2.3.1 实现代码

package cn.lyf.leetcode.thread.demo;

import lombok.extern.slf4j.Slf4j;

import static cn.lyf.leetcode.thread.demo.ThreadDemo1.sleep;

/**
 * @author lyf
 * @version 1.0
 * @classname ThreadDemo3
 * @description 方法说明
 *
 * 
 * 3. 使用线程的wait方法
 *
 * @since 2023/4/11 9:38
 */
@Slf4j
public class ThreadDemo3 {
    static final Object LOCK1 = new Object();
    static final Object LOCK2 = new Object();
    /**
     * 为什么要加这两个标识状态?
     * 如果没有状态标识，当thread-a已经运行完了thread-b才运行，
     * thread-b在等待thread-a唤醒导致thread-b永远处于等待状态
     */
    static boolean isRun1 = false;
    static boolean isRun2 = false;

    public static void main(String[] args) {
        new Thread(() -> {
            synchronized (LOCK1) {
                log.info("start...");
                sleep(100);
                log.info("end...");
                isRun1 = true;
                LOCK1.notify();
            }
        }, "thread-a").start();

        new Thread(() -> {
            synchronized (LOCK1) {
                while (!isRun1) {
                    try {
                        LOCK1.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                synchronized (LOCK2) {
                    log.info("start...");
                    sleep(100);
                    log.info("end...");
                    isRun2 = true;
                    LOCK2.notify();
                }
            }
        }, "thread-b").start();

        new Thread(() -> {
            synchronized (LOCK2) {
                while (!isRun2) {
                    try {
                        LOCK2.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                log.info("start...");
                sleep(100);
                log.info("end...");
            }
        }, "thread-c").start();
    }
}

2.3.2 运行结果

2023-04-11 10:09:54 [ thread-a ]  INFO ThreadDemo3:47 - start...
2023-04-11 10:09:54 [ thread-a ]  INFO ThreadDemo3:49 - end...
2023-04-11 10:09:54 [ thread-b ]  INFO ThreadDemo3:65 - start...
2023-04-11 10:09:54 [ thread-b ]  INFO ThreadDemo3:67 - end...
2023-04-11 10:09:54 [ thread-c ]  INFO ThreadDemo3:83 - start...
2023-04-11 10:09:54 [ thread-c ]  INFO ThreadDemo3:85 - end...

2.4 使用线程的线程池方法

JAVA通过Executors提供了四种线程池

• 单线程化线程池(newSingleThreadExecutor);
• 可控最大并发数线程池(newFixedThreadPool);
• 可回收缓存线程池(newCachedThreadPool);
• 支持定时与周期性任务的线程池(newScheduledThreadPool)。

**单线程化线程池(newSingleThreadExecutor)😗*优点，串行执行所有任务。

**submit()：**提交任务。

**shutdown()：**方法用来关闭线程池，拒绝新任务。

**应用场景:**串行执行所有任务。如果这个唯一的线程因为异常结束，那么会有一个新的线程来替代它。此线程池保证所有任务的执行顺序按照任务的提交顺序执行。

2.4.1 实现代码

package cn.lyf.leetcode.thread.demo;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import static cn.lyf.leetcode.thread.demo.ThreadDemo1.sleep;

/**
 * @author lyf
 * @version 1.0
 * @classname ThreadDemo1
 * @description 方法说明
 *
 * 4. 使用线程的线程池方法
 *
 * @since 2023/4/11 9:38
 */
@Slf4j
public class ThreadDemo4 {
    public static void main(String[] args) {
        ExecutorService poolExecutor = Executors.newSingleThreadExecutor();

        poolExecutor.submit(() -> {
            log.info("threadA start...");
            sleep(100);
            log.info("threadA end...");
        });

        poolExecutor.submit(() -> {
            log.info("threadB start...");
            sleep(100);
            log.info("threadB end...");
        });

        poolExecutor.submit(() -> {
            log.info("threadC start...");
            sleep(100);
            log.info("threadC end...");
        });

        poolExecutor.shutdown();
    }
}

2.4.2 运行结果

2023-04-11 10:27:11 [ pool-1-thread-1 ]  INFO ThreadDemo4:41 - threadA start...
2023-04-11 10:27:11 [ pool-1-thread-1 ]  INFO ThreadDemo4:43 - threadA end...
2023-04-11 10:27:11 [ pool-1-thread-1 ]  INFO ThreadDemo4:47 - threadB start...
2023-04-11 10:27:11 [ pool-1-thread-1 ]  INFO ThreadDemo4:49 - threadB end...
2023-04-11 10:27:11 [ pool-1-thread-1 ]  INFO ThreadDemo4:53 - threadC start...
2023-04-11 10:27:11 [ pool-1-thread-1 ]  INFO ThreadDemo4:55 - threadC end...

2.5 使用线程的Condition(条件变量)方法

**Condition（条件变量）😗*通常与一个锁关联。需要在多个Contidion中共享一个锁时，可以传递一个Lock/RLock实例给构造方法，否则它将自己生成一个RLock实例。

• Condition中await()方法类似于Object类中的wait()方法。
• Condition中await(long time,TimeUnit unit)方法类似于Object类中的wait(long time)方法。
• Condition中signal()方法类似于Object类中的notify()方法。
• Condition中signalAll()方法类似于Object类中的notifyAll()方法。

**应用场景：**Condition是一个多线程间协调通信的工具类，使得某个，或者某些线程一起等待某个条件（Condition）,只有当该条件具备( signal 或者 signalAll方法被调用)时 ，这些等待线程才会被唤醒，从而重新争夺锁。

2.5.1 实现代码

package cn.lyf.leetcode.thread.demo;

import lombok.extern.slf4j.Slf4j;

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

import static cn.lyf.leetcode.thread.demo.ThreadDemo1.sleep;

/**
 * @author lyf
 * @version 1.0
 * @classname ThreadDemo5
 * @description 方法说明
 * 
 * 5.使用线程的Condition（条件变量）方法
 *
 * @since 2023/4/11 9:38
 */
@Slf4j
public class ThreadDemo5 {
    static final Lock LOCK = new ReentrantLock();
    static final Condition CONDITION_A = LOCK.newCondition();
    static final Condition CONDITION_B = LOCK.newCondition();
    static boolean isRunA = false;
    static boolean isRunB = false;

    public static void main(String[] args) {
        new Thread(() -> {
            // 加锁
            LOCK.lock();
            log.info("start...");
            try {
                sleep(100);
            } catch (Exception e) {
                log.error("", e);
            } finally {
                isRunA = true;
                CONDITION_A.signal();
                // 解锁
                LOCK.unlock();
                log.info("end...");
            }
        }, "thread-a").start();

        new Thread(() -> {
            // 加锁
            LOCK.lock();
            while (!isRunA) {
                try {
                    CONDITION_A.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            log.info("start...");
            try {
                sleep(100);
            } catch (Exception e) {
                log.error("", e);
            } finally {
                isRunB = true;
                CONDITION_B.signal();
                // 解锁
                LOCK.unlock();
                log.info("end...");
            }
        }, "thread-b").start();

        new Thread(() -> {
            // 加锁
            LOCK.lock();
            while (!isRunB) { // 这里根据状态码，来使thread-c处于一直等待状态
                try {
                    CONDITION_B.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            log.info("start...");
            try {
                sleep(100);
            } catch (Exception e) {
                log.error("", e);
            } finally {
                // 解锁
                LOCK.unlock();
                log.info("end...");
            }
        }, "thread-c").start();
    }
}

2.5.2 运行结果

2023-04-11 10:34:06 [ thread-a ]  INFO ThreadDemo5:48 - start...
2023-04-11 10:34:06 [ thread-a ]  INFO ThreadDemo5:58 - end...
2023-04-11 10:34:06 [ thread-b ]  INFO ThreadDemo5:72 - start...
2023-04-11 10:34:06 [ thread-b ]  INFO ThreadDemo5:82 - end...
2023-04-11 10:34:06 [ thread-c ]  INFO ThreadDemo5:96 - start...
2023-04-11 10:34:06 [ thread-c ]  INFO ThreadDemo5:104 - end...

2.6 使用线程的CountDownLatch（倒计数）方法

**CountDownLatch:**位于java.util.concurrent包下，利用它可以实现类似计数器的功能。

**应用场景:**比如有一个任务C，它要等待其他任务A,B执行完毕之后才能执行，此时就可以利用CountDownLatch来实现这种功能了。

2.6.1 实现代码

package cn.lyf.leetcode.thread.demo;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.CountDownLatch;

import static cn.lyf.leetcode.thread.demo.ThreadDemo1.sleep;

/**
 * @author lyf
 * @version 1.0
 * @classname ThreadDemo6
 * @description 方法说明
 *
 * 
 * 6. 使用CountDownLatch（倒计数）的方法
 *
 * @since 2023/4/11 9:38
 */
@Slf4j
public class ThreadDemo6 {
    public static void main(String[] args) {
        CountDownLatch countDownLatchA = new CountDownLatch(1);
        CountDownLatch countDownLatchB = new CountDownLatch(1);
        new Thread(() -> {
            log.info("start...");
            sleep(100);
            log.info("end...");
            countDownLatchA.countDown();
        }, "thread-a").start();

        new Thread(() -> {
            try {
                countDownLatchA.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            log.info("start...");
            sleep(100);
            log.info("end...");
            countDownLatchB.countDown();
        }, "thread-b").start();

        new Thread(() -> {
            try {
                countDownLatchB.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            log.info("start...");
            sleep(100);
            log.info("end...");
        }, "thread-c").start();
    }
}

2.6.2 运行结果

2023-04-11 10:37:24 [ thread-a ]  INFO ThreadDemo6:40 - start...
2023-04-11 10:37:24 [ thread-a ]  INFO ThreadDemo6:42 - end...
2023-04-11 10:37:24 [ thread-b ]  INFO ThreadDemo6:52 - start...
2023-04-11 10:37:25 [ thread-b ]  INFO ThreadDemo6:54 - end...
2023-04-11 10:37:25 [ thread-c ]  INFO ThreadDemo6:64 - start...
2023-04-11 10:37:25 [ thread-c ]  INFO ThreadDemo6:66 - end...

2.7 使用线程的CyclicBarrier（回环栅栏）方法

**CyclicBarrier(回环栅栏)😗*通过它可以实现让一组线程等待至某个状态之后再全部同时执行。叫做回环是因为当所有等待线程都被释放以后，CyclicBarrier可以被重用。我们暂且把这个状态就叫做barrier，当调用await()方法之后，线程就处于barrier了。

**应用场景:**公司组织春游,等待所有的员工到达集合地点才能出发，每个人到达后进入barrier状态。都到达后，唤起大家一起出发去旅行。

2.7.1 实现代码

package cn.lyf.leetcode.thread.demo;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;

import static cn.lyf.leetcode.thread.demo.ThreadDemo1.sleep;

/**
 * @author lyf
 * @version 1.0
 * @classname ThreadDemo7
 * @description 方法说明
 *
 * 7. 使用线程的CyclicBarrier（回环栅栏）方法
 *
 * @since 2023/4/11 9:38
 */
@Slf4j
public class ThreadDemo7 {
    public static void main(String[] args) {
        CyclicBarrier cyclicBarrier1 = new CyclicBarrier(2);
        CyclicBarrier cyclicBarrier2 = new CyclicBarrier(2);
        new Thread(() -> {
            log.info("start...");
            sleep(100);
            log.info("end...");
            try {
                cyclicBarrier1.await();
            } catch (InterruptedException | BrokenBarrierException e) {
                e.printStackTrace();
            }
        }, "thread-a").start();

        new Thread(() -> {
            try {
                cyclicBarrier1.await();
            } catch (InterruptedException | BrokenBarrierException e) {
                e.printStackTrace();
            }
            log.info("start...");
            sleep(100);
            log.info("end...");


            try {
                cyclicBarrier2.await();
            } catch (InterruptedException | BrokenBarrierException e) {
                e.printStackTrace();
            }
        }, "thread-b").start();

        new Thread(() -> {
            try {
                cyclicBarrier2.await();
            } catch (InterruptedException | BrokenBarrierException e) {
                e.printStackTrace();
            }
            log.info("start...");
            sleep(100);
            log.info("end...");
        }, "thread-c").start();
    }
}

2.7.2 运行结果

2023-04-11 10:47:37 [ thread-a ]  INFO ThreadDemo7:41 - start...
2023-04-11 10:47:37 [ thread-a ]  INFO ThreadDemo7:43 - end...
2023-04-11 10:47:37 [ thread-b ]  INFO ThreadDemo7:57 - start...
2023-04-11 10:47:38 [ thread-b ]  INFO ThreadDemo7:59 - end...
2023-04-11 10:47:38 [ thread-c ]  INFO ThreadDemo7:75 - start...
2023-04-11 10:47:38 [ thread-c ]  INFO ThreadDemo7:77 - end...

2.8 使用Sephmore(信号量)实现线程按顺序运行

**Sephmore(信号量)😗*Semaphore是一个计数信号量,从概念上将，Semaphore包含一组许可证,如果有需要的话，每个acquire()方法都会阻塞，直到获取一个可用的许可证,每个release()方法都会释放持有许可证的线程，并且归还Semaphore一个可用的许可证。然而，实际上并没有真实的许可证对象供线程使用，Semaphore只是对可用的数量进行管理维护。

**acquire()😗*当前线程尝试去阻塞的获取1个许可证,此过程是阻塞的,当前线程获取了1个可用的许可证，则会停止等待，继续执行。

**release()😗*当前线程释放1个可用的许可证。

**应用场景:**Semaphore可以用来做流量分流，特别是对公共资源有限的场景，比如数据库连接。假设有这个的需求，读取几万个文件的数据到数据库中，由于文件读取是IO密集型任务，可以启动几十个线程并发读取，但是数据库连接数只有10个，这时就必须控制最多只有10个线程能够拿到数据库连接进行操作。这个时候，就可以使用Semaphore做流量控制。

2.8.1 实现代码

package cn.lyf.leetcode.thread.demo;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.Semaphore;

import static cn.lyf.leetcode.thread.demo.ThreadDemo1.sleep;

/**
 * @author lyf
 * @version 1.0
 * @classname ThreadDemo8
 * @description 方法说明
 * 
 * 8. 使用线程的Semaphore（信号量）方法
 *
 * @since 2023/4/11 9:38
 */
@Slf4j
public class ThreadDemo8 {
    public static void main(String[] args) {
        // 这里一定要将permits设置为0，只有设置为0 thread-a才会先执行，thread-b才会后执行
        Semaphore semaphore1 = new Semaphore(0);
        // 同上
        Semaphore semaphore2 = new Semaphore(0);
        new Thread(() -> {
            log.info("start...");
            sleep(100);
            log.info("end...");
            semaphore1.release();
        }, "thread-a").start();

        new Thread(() -> {
            try {
                semaphore1.acquire();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            log.info("start...");
            sleep(100);
            log.info("end...");
            semaphore1.release();
            semaphore2.release();
        }, "thread-b").start();

        new Thread(() -> {
            try {
                semaphore2.acquire();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            log.info("start...");
            sleep(100);
            log.info("end...");
            semaphore2.release();
        }, "thread-c").start();
    }
}

2.8.2 运行结果

2023-04-11 11:00:58 [ thread-a ]  INFO ThreadDemo8:42 - start...
2023-04-11 11:00:58 [ thread-a ]  INFO ThreadDemo8:44 - end...
2023-04-11 11:00:58 [ thread-b ]  INFO ThreadDemo8:54 - start...
2023-04-11 11:00:58 [ thread-b ]  INFO ThreadDemo8:56 - end...
2023-04-11 11:00:58 [ thread-c ]  INFO ThreadDemo8:67 - start...
2023-04-11 11:00:58 [ thread-c ]  INFO ThreadDemo8:69 - end...

2.9 使用LockSupport的park与unpark方法

java.util.concurrent.locks.LockSupport#park()

java.util.concurrent.locks.LockSupport#unpark(Thread thread)

• park：方法是使当前线程暂停运行
• unpark：方法是使指定线程恢复运行

2.9.1 实现代码

package cn.lyf.leetcode.thread.demo;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.locks.LockSupport;

import static cn.lyf.leetcode.thread.demo.ThreadDemo1.sleep;

/**
 * @author lyf
 * @version 1.0
 * @classname ThreadDemo9
 * @description 方法说明
 * 
 * 9. LockSupport
 * @since 2023/4/11 9:38
 */
@Slf4j
public class ThreadDemo9 {
    /**
     * 这里加标识，是为了保证threadA 在Unpark 时，ThreadB 已经处于Park状态了
     */
    static volatile boolean isRunA = false;

    /**
     * 这里加标识，是为了保证threadB 在Unpark 时，ThreadC 已经处于Park状态了
     */
    static volatile boolean isRunB = false;

    public static void main(String[] args) {

        Thread threadC = new Thread(() -> {
            while (!isRunB) {
                LockSupport.park();
            }
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
        }, "thread-c");

        Thread threadB = new Thread(() -> {
            while (!isRunA) {
                LockSupport.park();
            }
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
            isRunB = true;
            LockSupport.unpark(threadC);
        }, "thread-b");


        Thread threadA = new Thread(() -> {
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
            isRunA = true;
            LockSupport.unpark(threadB);
        }, "thread-a");

        threadC.start();
        threadB.start();
        threadA.start();
    }
}

2.9.2 运行结果

2023-04-11 11:25:20 [ thread-a ]  INFO ThreadDemo9:56 - start...
2023-04-11 11:25:20 [ thread-a ]  INFO ThreadDemo9:59 - end...
2023-04-11 11:25:20 [ thread-b ]  INFO ThreadDemo9:46 - start...
2023-04-11 11:25:20 [ thread-b ]  INFO ThreadDemo9:49 - end...
2023-04-11 11:25:20 [ thread-c ]  INFO ThreadDemo9:36 - start...
2023-04-11 11:25:20 [ thread-c ]  INFO ThreadDemo9:39 - end...

2.10 使用阻塞队列的put与take方法

阻塞队列的常用API

方法类型	抛出异常	特殊值	阻塞	超时
插入	add(e)	offer(e)	put(e)	offer(e, timeOut, unit)
移除	remove()	poll()	take()	poll(timeOut, unit)
检查	element()	peek()	不可用	不可用

本例主要是使用take操作的阻塞作用

2.10.1 实现代码

package cn.lyf.leetcode.thread.demo;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;

import static cn.lyf.leetcode.thread.demo.ThreadDemo1.sleep;

/**
 * @author lyf
 * @version 1.0
 * @classname ThreadDemo10
 * @description 方法说明
 * 
 * 10. 阻塞队列来实现
 * @since 2023/4/11 9:38
 */
@Slf4j
public class ThreadDemo10 {

    static volatile boolean isRunA = false;

    static volatile boolean isRunB = false;

    static BlockingQueue<Object> queue1 = new LinkedBlockingQueue<>();
    static BlockingQueue<Object> queue2 = new LinkedBlockingQueue<>();

    public static void main(String[] args) {
        final Object obj = new Object();
        Thread threadA = new Thread(() -> {
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
            isRunA = true;
            try {
                queue1.put(obj);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "thread-a");

        Thread threadB = new Thread(() -> {
            while (!isRunA) {
                try {
                    queue1.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
            isRunB = true;
            try {
                queue2.put(obj);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        }, "thread-b");

        Thread threadC = new Thread(() -> {
            while (!isRunB) {
                try {
                    queue2.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
        }, "thread-c");

        threadC.start();
        threadB.start();
        threadA.start();
    }
}

2.10.2 运行结果

2023-04-11 12:19:10 [ thread-a ]  INFO ThreadDemo10:32 - start...
2023-04-11 12:19:10 [ thread-a ]  INFO ThreadDemo10:35 - end...
2023-04-11 12:19:10 [ thread-b ]  INFO ThreadDemo10:52 - start...
2023-04-11 12:19:10 [ thread-b ]  INFO ThreadDemo10:55 - end...
2023-04-11 12:19:10 [ thread-c ]  INFO ThreadDemo10:73 - start...
2023-04-11 12:19:10 [ thread-c ]  INFO ThreadDemo10:76 - end...

2.11 使用CAS思想来实现线程的顺序运行（AtomicReference<Thread>）

compare and swap的缩写，中文翻译成比较并交换, 实现并发算法时常用到的一种技术。它包含三个操作数——内存位置、预期原值及更新值。

执行CAS操作的时候，将内存位置的值与预期原值比较：

如果相匹配，那么处理器会自动将该位置值更新为新值，

如果不匹配，处理器不做任何操作，多个线程同时执行CAS操作只有一个会成功。

2.11.1 实现代码

package cn.lyf.leetcode.thread.demo;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.atomic.AtomicReference;

import static cn.lyf.leetcode.thread.demo.ThreadDemo1.sleep;

/**
 * @author lyf
 * @version 1.0
 * @classname ThreadDemo11
 * @description 方法说明
 * <p>
 * 11. 使用CAS思想来完成多线程的顺序执行
 * @since 2023/4/11 9:38
 */
@Slf4j
public class ThreadDemo11 {
    public static void main(String[] args) {
        AtomicReference<Thread> threadAtomicReference = new AtomicReference<>();
        Thread threadA = new Thread(() -> {
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
            threadAtomicReference.set(Thread.currentThread());
        }, "thread-a");

        Thread threadB = new Thread(() -> {
            while (!threadAtomicReference.compareAndSet(threadA, null)) {
                sleep(1);
            }
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
            threadAtomicReference.set(Thread.currentThread());
        }, "thread-b");

        Thread threadC = new Thread(() -> {
            while (!threadAtomicReference.compareAndSet(threadB, null)) {
                sleep(1);
            }
            log.info("start...");
            // 模拟业务执行时长
            sleep(100);
            log.info("end...");
        }, "thread-c");

        threadC.start();
        threadB.start();
        threadA.start();
    }
}

2.11.2 运行结果

2023-04-11 14:06:32 [ thread-a ]  INFO ThreadDemo11:23 - start...
2023-04-11 14:06:32 [ thread-a ]  INFO ThreadDemo11:26 - end...
2023-04-11 14:06:32 [ thread-b ]  INFO ThreadDemo11:34 - start...
2023-04-11 14:06:32 [ thread-b ]  INFO ThreadDemo11:37 - end...
2023-04-11 14:06:32 [ thread-c ]  INFO ThreadDemo11:45 - start...
2023-04-11 14:06:33 [ thread-c ]  INFO ThreadDemo11:48 - end...

3 参考文章

• 多线程-顺序执行