多个线程顺序进行和轮询进行的问题

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废话不说了，晚上看到一个问题，需要ABC线程，能依次打印ABC（需要循环的）？

之前看能没有看到它需要循环打出这些，只是觉得他要顺序打出，所以就用了join 这个关键字做了一个demo；

package com.zeng.thread;/** * 实现三个线程ABC，按照顺序输出ABC * 方案一 *  * @author leo-zeng * */public class Test1 {public static void main(String[] args) throws Exception {//A 线程Thread t1 = new Thread(new Runnable() {public void run() {System.out.println("A");try {Thread.sleep(100);} catch (InterruptedException e) {e.printStackTrace();}}},"A");//b线程Thread t2 = new Thread(new Runnable() {public void run() {System.out.println("B");try {Thread.sleep(100);} catch (InterruptedException e) {e.printStackTrace();}}}, "B");//C 线程Thread t3 = new Thread(new Runnable() {public void run() {System.out.println("C");try {Thread.sleep(100);} catch (InterruptedException e) {e.printStackTrace();}}},"C");t1.start();t1.join();t2.start();t2.join();t3.start();}}

打印出的结果是ABC

后来仔细一看，不满足，问题的条件是需要循环打出ABC，所以用join 是不满足的，这会只能用到lock，通过condition来满足这个需求；下面也写了这个demo，

demo比较简单，通过一个reentrantLock 和 condition 的await 和single 方法，进行线程间的轮询，来达到结果；看下demo吧！

package com.zeng.thread;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.ReentrantLock;/** * Abc 三个线程分别输出循环输出 abc 用reentrantLock *  * @author leo-zeng *  */public class ReentrantLockDemo {public static void main(String[] args) {// 重入锁final ReentrantLock rLock = new ReentrantLock();// 三个conditionfinal Condition aCon = rLock.newCondition();final Condition bCon = rLock.newCondition();final Condition cCon = rLock.newCondition();//线程aThread a = new Thread(new Runnable() {public void run() {try {//先给第一个线程加上一段时间，给bc 线程 加锁 ，加信号Thread.sleep(500);} catch (InterruptedException e2) {// TODO Auto-generated catch blocke2.printStackTrace();}for (int i = 0; i < 3; i++) {try {// 加上锁rLock.lock();System.out.println("A");Thread.sleep(1000);// 打印完A 之后 关闭a 给b 信号bCon.signal();//等待一个a给的信号try {aCon.await();} catch (InterruptedException e1) {e1.printStackTrace();}} catch (InterruptedException e) {e.printStackTrace();} finally {// 解锁rLock.unlock();}}}}, "A");//线程bThread b = new Thread(new Runnable() {public void run() {for (int i = 0; i < 3; i++) {try {// 加上锁rLock.lock();try {//等待bconbCon.await();} catch (InterruptedException e2) {e2.printStackTrace();}System.out.println("B");Thread.sleep(1000);// 打印完b 之后  给c 信号cCon.signal();} catch (InterruptedException e) {e.printStackTrace();} finally {// 解锁rLock.unlock();}}}}, "B");//线程cThread c = new Thread(new Runnable() {public void run() {for (int i = 0; i <3; i++) {try {// 加上锁rLock.lock();try {//等待cconcCon.await();} catch (InterruptedException e2) {e2.printStackTrace();}System.out.println("C");Thread.sleep(1000);// 打印完c 之后  给a 信号aCon.signal();} catch (InterruptedException e) {e.printStackTrace();} finally {// 解锁rLock.unlock();}}}}, "C");//a b c 线程a.start();b.start();c.start();Thread.yield();}}

这里就不重点介绍ReentrantLock锁了；下次再和synchronized 一起对比介绍！

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