基于ZooKeeper实现队列源码

package org.massive.common; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooKeeper; import java.io.IOException; import java.util.concurrent.CountDownLatch; import java.util.concurrent.TimeUnit;  public class ZooKeeperClient {  private static String connectionString = "localhost:2181";  private static int sessionTimeout = 10000;  public static ZooKeeper getInstance() throws IOException, InterruptedException {  //--------------------------------------------------------------  // 为避免连接还未完成就执行zookeeper的get/create/exists操作引起的（KeeperErrorCode = ConnectionLoss)  // 这里等Zookeeper的连接完成才返回实例  //--------------------------------------------------------------  final CountDownLatch connectedSignal = new CountDownLatch(1);  ZooKeeper zk = new ZooKeeper(connectionString, sessionTimeout, new Watcher() {   @Override   public void process(WatchedEvent event) {    if (event.getState() == Event.KeeperState.SyncConnected) {    connectedSignal.countDown();    } else if (event.getState() == Event.KeeperState.Expired) {    }   }   });  connectedSignal.await(sessionTimeout, TimeUnit.MILLISECONDS);  return zk;  }  public static int getSessionTimeout() {  return sessionTimeout;  }  public static void setSessionTimeout(int sessionTimeout) {  ZooKeeperClient.sessionTimeout = sessionTimeout;  } }