Exception in thread "main" java.lang.NullPointerException thrown in zookeeper with java

Question

Zookeeper's throws following error when executing the compiled jar. I can't find what is causing that.

Exception in thread "main" java.lang.NullPointerException
        at org.apache.zookeeper.client.ConnectStringParser.<init>(ConnectStringParser.java:50)
        at org.apache.zookeeper.ZooKeeper.<init>(ZooKeeper.java:446)
        at org.apache.zookeeper.ZooKeeper.<init>(ZooKeeper.java:383)
        at ds.tutorials.sycnhronization.ZooKeeperClient.<init>(ZooKeeperClient.java:17)
        at ds.tutorials.sycnhronization.DistributedLock.<init>(DistributedLock.java:35)
        at ds.tutorials.communication.server.InventoryServer.<init>(InventoryServer.java:36)
        at ds.tutorials.communication.server.InventoryServer.main(InventoryServer.java:140)