public void connect () {
    try{
          Class.forName("com.mysql.jdbc.Driver");
          String servername = "potsdam-moodle.de";
          String datenbank = "e209123";
          String url = "jdbc:mysql://" + servername + "/" + datenbank;
          String username = "e209123";
          String password = "Wh3c#3a3";
          Connection connection = DriverManager.getConnection(url, username, password);
      } catch  (Exception e){
            e.printStackTrace();
            System.out.println("Error" + e);
       }
}

public void update(Float preis, String spalte) {
    try {
        connect();
        String query = "Update Produkte SET Preis= ? Where Name= ?";
        PreparedStatement st = connection.prepareStatement(query);
        st.setFloat(1,  preis);
        st.setString(2, spalte);
        st.executeUpdate();
      }
      catch  (Exception e){
        e.printStackTrace();
        System.out.println("Error" + e);
    }
}

tableView2Column2.setOnEditCommit(new EventHandler<CellEditEvent>() {   //Anfang
      public void handle(CellEditEvent t){
        update(Float.parseFloat(""+t.getNewValue()), ((Produkt) t.getTableView().getItems().get(t.getTablePosition().getRow())).getName());
    }
  }
);