Java程序之多线程顺序打印 ABC--Condition(推荐)

package abc3;

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

class ABCPrinter {//使用ReentrantLock + condition   //这里指的是三个线程总共打印100个
    private static final int PRINT_COUNT = 15;
    private static volatile int count = 0;//静态保证类的所有对象都共享一份  volatile保证可见性,禁止指令重排序


    private static final Lock lock = new ReentrantLock();
    private static final Condition conditionA = lock.newCondition();
    private static final Condition conditionB = lock.newCondition();
    private static final Condition conditionC = lock.newCondition();

    public static void main(String[] args) {
        new Thread(() -> println("a", conditionA, conditionB)).start();
        new Thread(() -> println("b", conditionB, conditionC)).start();
        new Thread(() -> println("c", conditionC, conditionA)).start();
    }

    private static void println(String str, Condition current, Condition next) {
        try {
            lock.lock();
            while (count < PRINT_COUNT) {
                while (count % 3 != getThreadIndex(str)) {//套while循环 防止虚假唤醒
                    current.await();
                }
                if (count < PRINT_COUNT) {//双重判断 防止最后阻塞的线程唤醒后 打印数字超过范围
                    System.out.println(Thread.currentThread().getName() + " : " + count + " : " + str);
                }
                count++;
                next.signal();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    private static int getThreadIndex(String str) {
        switch (str) {
            case "a":
                return 0;
            case "b":
                return 1;
            case "c":
                return 2;
            default:
                throw new IllegalArgumentException("Invalid thread name");
        }
    }
}