public void loadDevsFromDB(){

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

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

        Developer dev = 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, developers.bonus, "
                    + "dev_skills.skill, languages.language from employees"+
                                    " join developers on employees.id = developers.emp_id "
                                    + "join dev_skills on employees.id = dev_skills.emp_id "
                                    + "join languages on employees.id = languages.employee_id");
            while (rs.next())
            {
                if((dev == null) || (dev.getId() != rs.getInt("id"))) {
                    dev = new Developer(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 employee_id,language from languages where employee_id=" + dev.getId());*/
                }
                if(!dev.getLanguages().contains(rs.getString("language")))
                {
                    dev.addLanguage(rs.getString("language"));
                }
                if(!dev.showProgLang().contains(rs.getString("skill")))
                {
                    dev.addProgrammingLang(rs.getString("skill"));
                }
                dev.addDeveloper(dev);

            }
            //System.out.println(dev.toString() + " " + dev.getLanguages().toString());
            dev.giveAllDevs();
//          dev.giveDevsKeys().toString();

        } 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 ArrayList<String> showProgLang()
    {
        return this.programming_languages;
    }

public void giveAllDevs()
    {
        for(String dev_names: giveDevsKeys())
        {
            System.out.println(showDev(dev_names));
        }
    }

public Set<String> giveDevsKeys()
    {
        return developers.keySet();
    }

public Developer showDev(String first_last_name)
    {
        return developers.get(first_last_name.trim());
    }