public void loadManagersFromDB(){

        String jdbcUrl = "jdbc:postgresql://localhost/first_database";
        String username = "postgres";
        String password = "postgres";

        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;

        Manager man = null;

        try
        {
            conn = DriverManager.getConnection(jdbcUrl, username, password);
            stmt = conn.createStatement();
            rs = ((java.sql.Statement) stmt).executeQuery(
                    "select employees.id,employees.first_name,employees.last_name, "
                    + "employees.year_of_birth,employees.title,employees.monthly_salary, managers.bonus, "
                    + "languages.language from employees"
                    + " join managers on employees.id = managers.emp_id "
                    + "join languages on employees.id = languages.employee_id");
            while (rs.next())
            {

                if((man == null) || (man.getId() != rs.getInt("id"))) {
                    man = new Manager(rs.getInt("id"),rs.getString("first_name"),
                        rs.getString("last_name"),rs.getInt("year_of_birth"),
                        rs.getString("title"),rs.getFloat("monthly_salary"), rs.getFloat("bonus"));


                }

                ResultSet rs1 = null;
                rs1 = conn.createStatement().executeQuery("select subordinate from subordinates where manager=" + man.getId());

                if(!man.getLanguages().contains(rs.getString("language")))
                {
                    man.addLanguage(rs.getString("language"));
                }
                while(rs1.next()) {
                    for(String emp_names: keysOfEmps())
                    {
                        if(showEmp(emp_names).getId() == rs1.getInt("subordinate"))
                        {
                            for(String sub_names: giveSubsKeys())
                            {
                                if(showSub(sub_names).getId() != rs1.getInt("subordinate"))
                                {
                                    man.addSubordinates(showEmp(emp_names));
                                }
                            }
                        }
                    }
                }

                man.addManager(man);

            }

            man.showManagers();

        } catch (SQLException e)
        {
            e.printStackTrace();
        }
        finally
        {
            try {
                if (stmt != null) {
                    stmt.close();
                }
                if (rs != null) {
                    rs.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }


    }




public static Set<String> keysOfEmps()
    {
        return employees.keySet();
    }


public static Employee showEmp(String first_last_names)
    {
        return employees.get(first_last_names);
    }

public int getId()
    {
        if(id != 0)
        {
            return id;
        }
        else
        {
            return id;
        }
    }

public Set<String> giveSubsKeys()
    {
        return subordinates.keySet();
    }


public Employee showSub(String first_last)
    {
        return subordinates.get(first_last.trim());
    }


    public void showManagers()
    {
        for(String manager_names: getManagersKeys())
        {
            System.out.println(showManager(manager_names));
        }
    }