use strict;
use warnings;
use Net::SSH::Expect;
my $ssh = Net::SSH::Expect-> new(
    host => "host123",
    password => "passwd",
    user => "username",
    raw_pty => 1,
    timeout => 1,
);
$ssh->login();
$ssh->exec("su - root");
$ssh->exec("passwd");
$ssh->exec("su - user");
$ssh->exec("command1);
$ssh->exec("subcommand");
my $output = $ssh->exec("subcommand 2");
warn "$outputn";
$ssh->exec("n");
my $output2 = $ssh->exec("subcommand 3");
warn "$output2n";
$ssh->exec("n")

import java.io.InputStreamReader;
import ch.ethz.ssh2.Connection;
import ch.ethz.ssh2.SCPClient;
import ch.ethz.ssh2.Session;
import ch.ethz.ssh2.StreamGobbler;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
public void sshExecute() throws Exception {

String username = "username";
String password = "passwd";
    String hostname = "host123";
    logger.setLevel(Level.INFO);

    Object lastCommandOutput = null;
    logger.info("starting connection with "+hostname);
    Connection connection = new Connection(hostname);
    logger.info("connection object created..");
    connection.connect();
connection.authenticateWithPassword(username, password);
    Session session = connection.openSession();
    InputStream stdout = new StreamGobbler(session.getStdout());
BufferedReader stdoutReader = new BufferedReader(new InputStreamReader(stdout));
  logger.info("connected");

    String tempCommand = "su - root";
    String Pswd="passwd";
    logger.info("sending command: " + tempCommand);

    session.execCommand(tempCommand + Pswd);
    TimeUnit.SECONDS.sleep(5);

    session.execCommand("su - user");

  // Get output
    StringBuffer sb = new StringBuffer();
    while(true){
        String line = stdoutReader.readLine();
        if(line == null)
              break;
        sb.append(line+"n");
    }
    String output = sb.toString();
    lastCommandOutput = output;
    logger.info("got output: " + output);
    stdoutReader.close();
}

java.io.IOException: A remote execution has already started.  java.lang.Error: java.io.IOException: A remote execution has already started at com.user1.test.Assert.fail(Assert.java:35)