private void update(){
    connection();
    try{
        String sqldb =
                "update votersInfo set votersName = ? , age = ?,state = ? where votersId =?"
                ;
        prep = conn.prepareStatement(sqldb);

        //int intA = Integer.parseInt(jTextField1.getText());
        prep.setInt(1, Integer.parseInt(jTextField1.getText()));
        prep.setString(2, jTextField2.getText());
        prep.setInt(3, Integer.parseInt(jTextField3.getText()));
        prep.setString(4, jTextField4.getText());
        int a = prep.executeUpdate();
        if (a>0){
            JOptionPane.showMessageDialog(rootPane, "Sucessful");
        }
    }
    catch(Exception e){
       // System.err.println(e.printStackTrace());
        e.printStackTrace();
    }
}

String sqldb =
            "update votersInfo set votersName = ? [1], age = ? [2] ,state = ? [3] where votersId =? [4]";

prep.setInt(1, Integer.parseInt(jTextField1.getText())); //setting name to an Integer
    prep.setString(2, jTextField2.getText()); //setting age to a String
    prep.setInt(3, Integer.parseInt(jTextField3.getText())); //setting state to an Integer
    prep.setString(4, jTextField4.getText()); //setting votersId to a String