CountDownLatch闭锁
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CountDownLatch闭锁
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CountDownLatch :閉鎖,在完成某些運(yùn)算時(shí),只有其他所有線程的運(yùn)算全部完成,當(dāng)前運(yùn)算才繼續(xù)執(zhí)行
方法:
countDown?():減少鎖存器的計(jì)數(shù),如果計(jì)數(shù)達(dá)到零,釋放所有等待的線程
await?():導(dǎo)致當(dāng)前線程等到鎖存器向下計(jì)數(shù)為零,除非線程為 interrupted
案例分析:
我們要統(tǒng)計(jì)50個(gè)線程執(zhí)行完LatchDemo中的run()之后的時(shí)間,這時(shí)我們需要在LatchDemo中定義一個(gè)CountDownLatch閉鎖 CountDownLatch創(chuàng)建的時(shí)候可以給定一個(gè)初始化值
?
public class CountDownLatchTest {public static void main(String[] args) {//構(gòu)造一個(gè)以給定計(jì)數(shù)初始化的 CountDownLatch//初始值即為要統(tǒng)計(jì)的線程數(shù)final CountDownLatch latch = new CountDownLatch(50);LatchDemo ld = new LatchDemo(latch);long start = System.currentTimeMillis();for (int i = 0; i < 50; i++) {new Thread(ld).start();}/*調(diào)用CountDownLatch的await()方法,只有該對(duì)象的鎖存器計(jì)數(shù)為0時(shí),即線程全部走完后,程序才會(huì)繼續(xù)往下走這時(shí)就能統(tǒng)計(jì)出來(lái)50個(gè)線程都執(zhí)行完之后的時(shí)間*/try {latch.await();} catch (InterruptedException e) {}long end = System.currentTimeMillis();System.out.println("耗費(fèi)時(shí)間為:" + (end - start));}}class LatchDemo implements Runnable {private CountDownLatch latch;public LatchDemo(CountDownLatch latch) {this.latch = latch;}@Overridepublic void run() {try {for (int i = 0; i < 50000; i++) {if (i % 2 == 0) {System.out.println(i);}}} finally {//當(dāng)線程執(zhí)行完run方法之后,調(diào)用countDown()使鎖存器計(jì)數(shù)減1latch.countDown();}}}?
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