在多線程開發(fā)中，常常遇到希望一組線程完成之后在執(zhí)行之后的操作，java提供了一個(gè)多線程同步輔助類，可以完成此類需求：
類中常見的方法：
其中構(gòu)造方法：
CountDownLatch(int count) 參數(shù)count是計(jì)數(shù)器，一般用要執(zhí)行線程的數(shù)量來賦值。
long getCount()：獲得當(dāng)前計(jì)數(shù)器的值。
void countDown()：當(dāng)計(jì)數(shù)器的值大于零時(shí)，調(diào)用方法，計(jì)數(shù)器的數(shù)值減少1，當(dāng)計(jì)數(shù)器等數(shù)零時(shí)，釋放所有的線程。
void await()：調(diào)所該方法阻塞當(dāng)前主線程，直到計(jì)數(shù)器減少為零。
代碼例子：
線程類：
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import java.util.concurrent.CountDownLatch;public class TestThread extends Thread{CountDownLatch cd;String threadName;public TestThread(CountDownLatch cd,String threadName){ this.cd=cd; this.threadName=threadName;}@Overridepublic void run() { System.out.println(threadName+" start working..."); dowork(); System.out.println(threadName+" end working and exit..."); cd.countDown();//告訴同步類完成一個(gè)線程操作完成}private void dowork(){ try { Thread.sleep(2000); System.out.println(threadName+" is working..."); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }}} |
測(cè)試類：
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import java.util.concurrent.CountDownLatch;public class TsetCountDownLatch { public static void main(String[] args) { try { CountDownLatch cd = new CountDownLatch(3);// 表示一共有三個(gè)線程 TestThread thread1 = new TestThread(cd, "thread1"); TestThread thread2 = new TestThread(cd, "thread2"); TestThread thread3 = new TestThread(cd, "thread3"); thread1.start(); thread2.start(); thread3.start(); cd.await();//等待所有線程完成 System.out.println("All Thread finishd"); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } }} |
輸出結(jié)果：
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thread1 start working...thread2 start working...thread3 start working...thread2 is working...thread2 end working and exit...thread1 is working...thread3 is working...thread3 end working and exit...thread1 end working and exit...All Thread finishd |
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原文鏈接：http://www.cnblogs.com/ITer-jack/p/6791803.html
