java connects to Linux channel to execute shell script

package com.test.linux;

import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;

import org.apache.commons.io.IOUtils;

import ch.ethz.ssh2.ChannelCondition;
import ch.ethz.ssh2.Connection;
import ch.ethz.ssh2.Session;
import ch.ethz.ssh2.StreamGobbler;

public class RemoteShellExecutor {
     
     private Connection conn;
     /** Remote machine IP */
     private String ip;
     /** username*/
     private String osUsername;
     /** password*/
     private String password;
     private String charset = Charset.defaultCharset().toString();

     private static final int TIME_OUT = 1000 * 5 * 60;

     /**
      * Constructor
      * @paramip
      * @param usr
      * @param password
      */
     public RemoteShellExecutor(String ip, String usr, String pasword) {
          this.ip = ip;
         this.osUsername = usr;
         this.password = pasword;
     }


     /**
     * Log in
     * @return
     * @throws IOException
     */
     private boolean login() throws IOException {
         conn = new Connection(ip);
         conn.connect();
         return conn.authenticateWithPassword(osUsername, password);
     }

     /**
     * Execute the script
     *
     * @param cmds
     * @return
     * @throws Exception
     */
     public int exec(String cmds) throws Exception {
         InputStream stdOut = null;
         InputStream stdErr = null;
         String outStr = "";
         String outErr = "";
         int ret = -1;
         try {
         if (login()) {
             // Open a new {@link Session} on this connection
             Session session = conn.openSession();
             // Execute a command on the remote machine.
             session.execCommand(cmds);
             
             stdOut = new StreamGobbler(session.getStdout());
             outStr = processStream(stdOut, charset);
             
             stdErr = new StreamGobbler(session.getStderr());
             outErr = processStream(stdErr, charset);
             
             session.waitForCondition(ChannelCondition.EXIT_STATUS, TIME_OUT);
             
             System.out.println("outStr=" + outStr);
             System.out.println("outErr=" + outErr);
             
             ret = session.getExitStatus();
         } else {
             throw new Exception("Failed to log in to the remote machine" + ip); // The implementation of the custom exception class is omitted
         }
         } finally {
             if (conn != null) {
                 conn.close();
             }
             IOUtils.closeQuietly(stdOut);
             IOUtils.closeQuietly(stdErr);
         }
         return ret;
     }

     /**
     * @param in
     * @param charset
     * @return
     * @throws IOException
     * @throws UnsupportedEncodingException
     */
     private String processStream(InputStream in, String charset) throws Exception {
         byte[] buf = new byte[1024];
         StringBuilder sb = new StringBuilder();
         while (in.read(buf) != -1) {
             sb.append(new String(buf, charset));
         }
         return sb.toString();
     }

    public static void main(String args[]) throws Exception {
        RemoteShellExecutor executor = new RemoteShellExecutor("172.xx.x.xxx", "root", "DSJdsj171");
        
        System.out.println(executor.exec("/usr/hqmart/nfs/nfsJob.sh")); //shell script file on linux system
    }
}