Java中CountDownLatch用法解析
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2024-03-08 21:36:46
countdownlatch类是一个同步计数器,构造时传入int参数,该参数就是计数器的初始值,每调用一次countdown()方法,计数器减1,计数器大于0 时,awai...
countdownlatch类是一个同步计数器,构造时传入int参数,该参数就是计数器的初始值,每调用一次countdown()方法,计数器减1,计数器大于0 时,await()方法会阻塞程序继续执行
countdownlatch如其所写,是一个倒计数的锁存器,当计数减至0时触发特定的事件。利用这种特性,可以让主线程等待子线程的结束。下面以一个模拟运动员比赛的例子加以说明。
import java.util.concurrent.countdownlatch; import java.util.concurrent.executor; import java.util.concurrent.executorservice; import java.util.concurrent.executors; public class countdownlatchdemo { private static final int player_amount = 5; public countdownlatchdemo() { // todo auto-generated constructor stub } /** * @param args */ public static void main(string[] args) { // todo auto-generated method stub //对于每位运动员,countdownlatch减1后即结束比赛 countdownlatch begin = new countdownlatch(1); //对于整个比赛,所有运动员结束后才算结束 countdownlatch end = new countdownlatch(player_amount); player[] plays = new player[player_amount]; for(int i=0;i<player_amount;i++) plays[i] = new player(i+1,begin,end); //设置特定的线程池,大小为5 executorservice exe = executors.newfixedthreadpool(player_amount); for(player p:plays) exe.execute(p); //分配线程 system.out.println("race begins!"); begin.countdown(); try{ end.await(); //等待end状态变为0,即为比赛结束 }catch (interruptedexception e) { // todo: handle exception e.printstacktrace(); }finally{ system.out.println("race ends!"); } exe.shutdown(); } }
接下来是player类
import java.util.concurrent.countdownlatch; public class player implements runnable { private int id; private countdownlatch begin; private countdownlatch end; public player(int i, countdownlatch begin, countdownlatch end) { // todo auto-generated constructor stub super(); this.id = i; this.begin = begin; this.end = end; } @override public void run() { // todo auto-generated method stub try{ begin.await(); //等待begin的状态为0 thread.sleep((long)(math.random()*100)); //随机分配时间,即运动员完成时间 system.out.println("play"+id+" arrived."); }catch (interruptedexception e) { // todo: handle exception e.printstacktrace(); }finally{ end.countdown(); //使end状态减1,最终减至0 } } }
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