CountDownLatch和CyclicBarrier的主要联系和区别如下：
1.闭锁CountDownLatch做减计数，而栅栏CyclicBarrier则是加计数。
2.CountDownLatch是一次性的，CyclicBarrier可以重用。
3.CountDownLatch强调一个线程等多个线程完成某件事情。CyclicBarrier是多个线程互等，等大家都完成。
4.鉴于上面的描述，CyclicBarrier在一些场景中可以替代CountDownLatch实现类似的功能。

另外，值得一提的是，CountDownLatch和CyclicBarrier在创建和启动线程时，都没有明确提到同时启动全部线程，事实上这在技术上是不大可能，不必要，不提倡的。

先看例子一：

class SubRunnable implements Runnable {private CountDownLatch begin, end;private List<Integer> sublist;public SubRunnable(List<Integer> sublist, CountDownLatch begin,CountDownLatch end) {this.sublist = sublist;this.begin = begin;this.end = end;}@Overridepublic void run() {try {begin.await();            if (sublist != null) {for (int i : sublist) {System.out.println("线程" + Thread.currentThread().getName() + ", i = " + i);}}} catch (InterruptedException e) {e.printStackTrace();} finally{System.out.println(System.currentTimeMillis() + ",线程" + Thread.currentThread().getName() + ",开始执行！");end.countDown();}}
}
public class BatchWithCountDownLatch {private static final int MAX = 3;private static void list(List<Integer> list) {if(list == null){list = new ArrayList<Integer>();}for(int i = 0 ;i < 1000;i++){list.add(i);}}public static void main(String[] args) {List<Integer> list = new ArrayList<Integer>();list(list);//把list拆分成多个int mod = list.size() % MAX;int threadCount = mod == 0 ? list.size() / MAX : list.size() / MAX + 1;ExecutorService executors = Executors.newFixedThreadPool(threadCount);CountDownLatch begin = new CountDownLatch(1); CountDownLatch end = new CountDownLatch(threadCount); for(int i = 0; i< threadCount;i++){int subsize = (i + 1) * MAX;executors.execute(new SubRunnable(list.subList(i * MAX, subsize > list.size() ? list.size() : subsize),begin,end));}System.out.println("开始 !");begin.countDown();long startTime = System.currentTimeMillis();try {end.await();} catch (InterruptedException e) {e.printStackTrace();} finally {System.out.println("线程" + Thread.currentThread().getName() + "," + System.currentTimeMillis() + ", 所有线程已完成，开始进入下一步！");System.out.println("花费时间 -> " + (System.currentTimeMillis() - startTime) + " ms");}System.out.println("开始进入第二步操作! ");        System.out.println("end! ");}
}

这是根据jdk文档中的伪代码例程，编写的一个例子，我们完全可以将这个例程改为只使用一个CountDownLatch来实现之。经过测试，发现begin的引入对程序基本无用，当list是1000的数量级时，最先启动的线程仍然比最后启动的快几十毫秒左右；而不设置begin开始闭锁的程序，也是完全一样的情况。

例子二：

class SubRunnable implements Runnable {private CyclicBarrier cyclicBarrier;private List<Integer> sublist;public SubRunnable(List<Integer> sublist, CyclicBarrier cyclicBarrier) {this.sublist = sublist;this.cyclicBarrier = cyclicBarrier;}@Overridepublic void run() {        try {System.out.println(System.currentTimeMillis() + ",线程" + Thread.currentThread().getName() + ",开始执行！");if(sublist != null){for(int i : sublist){System.out.println("线程" + Thread.currentThread().getName() + ", i = " + i);}}cyclicBarrier.await();} catch (InterruptedException | BrokenBarrierException e) {e.printStackTrace();}}
}
public class ReplaceCountDownLatch {private static final int MAX = 3;private static void list(List<Integer> list) {if(list == null){list = new ArrayList<Integer>();}for(int i = 0 ;i < 10;i++){list.add(i);}}public static void main(String[] args) throws InterruptedException, BrokenBarrierException {List<Integer> list = new ArrayList<Integer>();list(list);//把list拆分成多个int mod = list.size() % MAX;int threadCount = mod == 0 ? list.size() / MAX : list.size() / MAX + 1;ExecutorService executors = Executors.newFixedThreadPool(threadCount);final CyclicBarrier cyclicBarrier = new CyclicBarrier(threadCount,new Runnable() {@Overridepublic void run() {//根据jdkdoc里的描述，哪个线程最后运行完，就执行下面的代码。System.out.println("线程" + Thread.currentThread().getName() + "," + System.currentTimeMillis() + ", 所有线程已完成，开始进入下一步！");}});for(int i = 0; i< threadCount;i++){int subsize = (i + 1) * MAX;executors.execute(new SubRunnable(list.subList(i * MAX, subsize > list.size() ? list.size() : subsize),cyclicBarrier));}cyclicBarrier.await();executors.shutdown();System.out.println("开始进入第二步操作! ");System.out.println("end! ");}
}

使用栅栏CyclicBarrier实现和上面闭锁CountDownLatch相同的功能。