Acesso a banco falhas

public void validaSenha(){
   String dbURL ="jdbc:derby://localhost/sample";
   String usuarioBanco = "app";
   String senhaBanco = "app";

   try {
        Class.forName("org.apache.derby.jdbc.ClientDriver");
        connection = DriverManager.getConnection(dbURL, usuarioBanco, senhaBanco);
   }
   catch (ClassNotFoundException cnfex) {
          System.err.println(
          "");
          cnfex.printStackTrace();
          System.exit(1);
   }
   catch (SQLException sqlex) {
          System.err.println("");
          sqlex.printStackTrace();
   }
   
}
public ResultSet  getSenha(){
    Statement statement;
    ResultSet resultset;

    try {
    String query = "Select nivel_acesso from senha_programa where senha = " +
            " ' " + JOptionPane.showInputDialog("Digite sua senha") + " ' ";
    statement = connection.createStatement();
    resultset = statement.executeQuery(query);
    //JOptionPane.showMessageDialog(null, resultset);
    statement.close();
    return resultset;
    }
    catch ( SQLException sqlex ) {
    sqlex.printStackTrace();
    return null;
    }
}
public String retornaSenha(){
    String senha = getSenha().toString();
    //JOptionPane.showMessageDialog(null, senha);
    return senha;

}