CountDownLatch類(lèi)是一個(gè)同步計(jì)數(shù)器,構(gòu)造時(shí)傳入int參數(shù),該參數(shù)就是計(jì)數(shù)器的初始值，每調(diào)用一次countDown()方法，計(jì)數(shù)器減1,計(jì)數(shù)器大于0 時(shí)，await()方法會(huì)阻塞程序繼續(xù)執(zhí)行
CountDownLatch如其所寫(xiě)，是一個(gè)倒計(jì)數(shù)的鎖存器，當(dāng)計(jì)數(shù)減至0時(shí)觸發(fā)特定的事件。利用這種特性，可以讓主線程等待子線程的結(jié)束。下面以一個(gè)模擬運(yùn)動(dòng)員比賽的例子加以說(shuō)明。
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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 //對(duì)于每位運(yùn)動(dòng)員，CountDownLatch減1后即結(jié)束比賽 CountDownLatch begin = new CountDownLatch(1); //對(duì)于整個(gè)比賽，所有運(yùn)動(dòng)員結(jié)束后才算結(jié)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); //設(shè)置特定的線程池，大小為5 ExecutorService exe = Executors.newFixedThreadPool(PLAYER_AMOUNT); for(Player p:plays) exe.execute(p); //分配線程 System.out.println("Race begins!"); begin.countDown(); try{ end.await(); //等待end狀態(tài)變?yōu)?，即為比賽結(jié)束 }catch (InterruptedException e) { // TODO: handle exception e.printStackTrace(); }finally{ System.out.println("Race ends!"); } exe.shutdown(); }} |
接下來(lái)是Player類(lèi)
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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的狀態(tài)為0 Thread.sleep((long)(Math.random()*100)); //隨機(jī)分配時(shí)間，即運(yùn)動(dòng)員完成時(shí)間 System.out.println("Play"+id+" arrived."); }catch (InterruptedException e) { // TODO: handle exception e.printStackTrace(); }finally{ end.countDown(); //使end狀態(tài)減1，最終減至0 } } } |
以上就是本文的全部?jī)?nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持服務(wù)器之家。
