【Java多线程实战设计】用三个线程按顺序循环打印abc三个字母，比如abcabcabc java多线程

目录
1 思路
2 synchronized/wait/notifyAll 机制
3 ReentrantLock/Condition.await()/Condition.signalAll() 机制
1 思路启动三个线程，采用多线程间等待/通知的机制来设计。维护一个全局不变数组printArr和变量索引index，printArr[index]就是接下来的线程要打印的字符。三个线程一开始就定好了打印的字符，当线程获取锁后，要判断printArr[index]与指定该线程的字符相等，相等就打印字符同时index = (index+1)%3，不相等表明还没轮到当前线程打印，当前线程等待。
2 synchronized/wait/notifyAll 机制

public class Test1 {private static char[] printArr = new char[]{'a','b','c'}; private static volatile int index; // 保证index的可见性public static void main(String[] args) { ExecutorService threadPool = Executors.newFixedThreadPool(3); final Object lock = new Object(); threadPool.execute(new MyThread(lock,printArr[index])); threadPool.execute(new MyThread(lock,printArr[index+1])); threadPool.execute(new MyThread(lock,printArr[index+2])); threadPool.shutdown(); }private static class MyThread extends Thread{// 静态内部打印类 Object lock; // 同步锁和等待/通知锁 char printC; // 指定的要打印的字符 MyThread(final Object lock ,char printC){ this.lock = lock; this.printC = printC; }@Override public void run(){ while(true){ synchronized (lock){ char c = printArr[index]; if (c == printC){ System.out.println(c); index = (index+1)%printArr.length; // index“+1” lock.notifyAll(); // 唤醒所有等待在lock上的线程 } else { try { lock.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } } } } } }

3 ReentrantLock/Condition.await()/Condition.signalAll() 机制

public class Test2 {private static char[] printArr = new char[]{'a','b','c'}; private static volatile int index; // 保证index的可见性public static void main(String[] args) { ExecutorService threadPool = Executors.newFixedThreadPool(3); ReentrantLock lock = new ReentrantLock(); Condition condition = lock.newCondition(); threadPool.execute(new MyThread(lock,condition,printArr[index])); threadPool.execute(new MyThread(lock,condition,printArr[index+1])); threadPool.execute(new MyThread(lock,condition,printArr[index+2])); threadPool.shutdown(); }private static class MyThread extends Thread{// 静态内部打印类 ReentrantLock lock; Condition condition; char printC; // 指定的要打印的字符MyThread(ReentrantLock lock ,Condition condition ,char printC){ if (lock == null || condition == null) throw new NullPointerException("lock or condition is null"); this.lock = lock; this.condition = condition; this.printC = printC; }@Override public void run(){ while(true){ lock.lock(); try { char c = printArr[index]; if (c == printC){ System.out.println(c); index = (index+1)%printArr.length; condition.signalAll(); } else { try { condition.await(); } catch (InterruptedException e) { e.printStackTrace(); } } }finally { lock.unlock(); } } } } }

【【Java多线程实战设计】用三个线程按顺序循环打印abc三个字母，比如abcabcabc】