public class Acesso {

    public boolean acesso;

    public void Acessar (String login, String senha){
        Connection conexao = null;
        Statement stmt = null;
        ResultSet tabela = null;


        try{
            Class.forName("com.mysql.jdbc.Driver");
            conexao = DriverManager.getConnection("jdbc:mysql://127.0.0.1/cadastro_potato", "root", "");
            stmt = (Statement) conexao.createStatement();
            tabela = stmt.executeQuery("select login, senha from usuario where login ='"+ login + "'and senha ='"+senha+"'");

            if(tabela.next()){

                acesso = true;
            }else{
                JOptionPane.showMessageDialog(null, "Usuário e Senha Incorretos");
                acesso = false;
            }


        }catch(ClassNotFoundException | SQLException ex){

        }
    }
}