多线程交替打印ABC

Java管程实现

class Solution {

    static final Object lock = new Object();
    static int state = 0;

    public static void main(String[] args) {
        Thread a = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                synchronized (lock) {
                    while (state % 3 != 0) {
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            throw new RuntimeException(e);
                        }
                    }
                    System.out.println("A");
                    state++;
                    lock.notifyAll();
                }
            }
        });
        Thread b = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                synchronized (lock) {
                    while (state % 3 != 1) {
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            throw new RuntimeException(e);
                        }
                    }
                    System.out.println("B");
                    state++;
                    lock.notifyAll();
                }
            }
        });
        Thread c = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                synchronized (lock) {
                    while (state % 3 != 2) {
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            throw new RuntimeException(e);
                        }
                    }
                    System.out.println("C");
                    state++;
                    lock.notifyAll();
                }
            }
        });
        a.start();
        b.start();
        c.start();
    }
}

ReentrantLock实现

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

class Solution {

    static final ReentrantLock lock = new ReentrantLock();
    static final Condition printA = lock.newCondition();
    static final Condition printB = lock.newCondition();
    static final Condition printC = lock.newCondition();
    static int state = 0;

    public static void main(String[] args) {
        Thread a = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                lock.lock();
                try {
                    while (state % 3 != 0) {
                        printA.await();
                    }
                    System.out.println("A");
                    state++;
                    printB.signal();
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                } finally {
                    lock.unlock();
                }
            }
        });
        Thread b = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                lock.lock();
                try {
                    while (state % 3 != 1) {
                        printB.await();
                    }
                    System.out.println("B");
                    state++;
                    printC.signal();
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                } finally {
                    lock.unlock();
                }
            }
        });
        Thread c = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                lock.lock();
                try {
                    while (state % 3 != 2) {
                        printC.await();
                    }
                    System.out.println("C");
                    state++;
                    printA.signal();
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                } finally {
                    lock.unlock();
                }
            }
        });
        a.start();
        b.start();
        c.start();
    }
}