public static void main(String[] arg) throws JSchException, InterruptedException {
    JSch jsch = new JSch();

    String[] proxyInfo = queryUserAndHost("proxy server", arg.length > 0 ? arg[0] : null);

    Session gateway = jsch.getSession(proxyInfo[0], proxyInfo[1]);

    UserInfo ui = new SwingDialogUserInfo();
    gateway.setUserInfo(ui);
    gateway.connect();

    String[] targetInfo = queryUserAndHost("target server", arg.length > 1 ? arg[1] : null);

    Session session = jsch.getSession(targetInfo[0], targetInfo[1]);

    session.setProxy(new ProxySSH(gateway));

    session.setUserInfo(ui);

    System.err.println("connecting session ...");
    session.connect();

    System.err.println("session connected.");
    System.err.println("opening shell channel ...");

    Channel channel = session.openChannel("shell");

    channel.setOutputStream(System.out, true);
    channel.setExtOutputStream(System.err, true);

    channel.setInputStream(System.in, true);

    channel.connect();

    System.err.println("shell channel connected.");

    do {
      Thread.sleep(100);
    } while (!channel.isEOF());
    System.err.println("exitcode: " + channel.getExitStatus());
    session.disconnect();
    Thread.sleep(50);

    gateway.disconnect();
  }