call from java.net.unknownhostexception: ubuntu-larntin: ubuntu-larntin to localhost:9000 failed on connection exception: java.net.connectexception: connection refused;

wrr@ubuntu:~$ hadoop namenode -format

wrr@ubuntu:~$ cd /home/wrr/java/hadoop-2.7.6/sbin
wrr@ubuntu:~/java/hadoop-2.7.6/sbin$ ./hadoop-daemon.sh start namenode
starting namenode, logging to /home/wrr/java/hadoop-2.7.6/logs/hadoop-wrr-namenode-ubuntu.out
wrr@ubuntu:~/java/hadoop-2.7.6/sbin$ jps
8307 datanode
9317 namenode
7431 
9352 jps
8476 resourcemanager

import org.apache.hadoop.conf.configuration;
import org.apache.hadoop.fs.filesystem;
import org.apache.hadoop.fs.path;
public class hdfsfileifexist {
    public static void main(string[] args){
        try{
            string filename = "test";
            configuration conf = new configuration();
            conf.set("fs.defaultfs", "hdfs://localhost:9000");
            conf.set("fs.hdfs.impl", "org.apache.hadoop.hdfs.distributedfilesystem");
            filesystem fs = filesystem.get(conf);
            if(fs.exists(new path(filename))){
                system.out.println("文件存在");
            }else{
                system.out.println("文件不存在");
            }
 
        }catch (exception e){
            e.printstacktrace();
        }
    }
}