顺序打印-进阶版

方法一：三个线程竞争同一个锁，通过count判断是否打印

方法二：三个线程同时start，分别上锁，从a开始，打印后唤醒b

三个线程分别打印A，B，C
方法一：通过count计数打印（三个线程上同样的锁，打印一个，召唤所有锁，如果不满足条件，则wait等待，锁自动解锁）
方法二：

/**
 * 有三个线程，分别只能打印A，B和C
 * 要求按顺序打印ABC，打印10次
 * 输出示例：
 * ABC
 * ABC
 * ABC
 * ABC
 * ABC
 * ABC
 * ABC
 * ABC
 * ABC
 * ABC
 */
public class Thread_ {
    // 计数器
    private static volatile int COUNTER = 0;
    // 定义一个单独的锁对象
    private static Object lock = new Object();

    public static void main(String[] args) {
        // 创建三个线程，并指定线程名，每个线程名分别用A,B,C表示
        Thread t1 = new Thread(() -> {
            // 循环10次
            for (int i = 0; i < 10; i++) {
                // 执行的代码加锁
                synchronized (lock) {
                    // 每次唤醒后都重新判断是否满足条件// 每条线程判断的条件不一样，注意线程t1,t2
                    while (COUNTER % 3 != 0) {
                        try {
                            // 不满足输出条件时，主动等待并释放锁
                            lock.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                    // 满足输出条件，打印线程名，每条线程打印的内容不同
                    System.out.print(Thread.currentThread().getName());
                    // 累加计数
                    COUNTER++;
                    // 唤醒其他线程
                    lock.notifyAll();
                }
            }
        }, "A");

        Thread t2 = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                synchronized (lock) {
                    while (COUNTER % 3 != 1) {
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                    System.out.print(Thread.currentThread().getName());
                    COUNTER++;
                    lock.notifyAll();
                }
            }
        }, "B");

        Thread t3 = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                synchronized (lock) {
                    while (COUNTER % 3 != 2) {
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }

                    // 换行打印
                    System.out.println(Thread.currentThread().getName());
                    COUNTER++;
                    lock.notifyAll();
                }
            }
        }, "C");

        // 启动线程
        t1.start();
        t2.start();
        t3.start();
    }
}

public class Demo {
    private static Object locker1 = new Object();
    private static Object locker2 = new Object();
    private static Object locker3 = new Object();

    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(() -> {
            try {
                for (int i = 0; i < 10; i++) {
                    synchronized (locker1) {
                        locker1.wait();
                    }
                    System.out.print("A");
                    synchronized (locker2) {
                        locker2.notify();
                    }
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });

        Thread t2 = new Thread(() -> {
            try {
                for (int i = 0; i < 10; i++) {
                    synchronized (locker2) {
                        locker2.wait();
                    }
                    System.out.print("B");
                    synchronized (locker3) {
                        locker3.notify();
                    }
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });

        Thread t3 = new Thread(() -> {
            try {
                for (int i = 0; i < 10; i++) {
                    synchronized (locker3) {
                        locker3.wait();
                    }
                    System.out.println("C");
                    synchronized (locker1) {
                        locker1.notify();
                    }
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        t1.start();
        t2.start();
        t3.start();

        Thread.sleep(1000);

        // 从线程 t1 启动
        synchronized (locker1) {
            locker1.notify();
        }
    }
}