title: NullPointerException when using executeQuery
body: <p>I have a null pointer exception in </p>
  
  <pre><code>ResultSet rs = aStatement.executeQuery(Query); // it can't be executed 
  </code></pre>
  
  <p>my code is like this :</p>
  
  <pre><code> public static boolean testLogin(String user, String password) throws SQLException {
      String Query = "select * from TBL_Users where userName = '" + user + "' and  passWord = '" + password + "' ";
      ResultSet rs = aStatement.executeQuery(Query);
  
      while (rs.next()) {
  
          info.Id = rs.getInt("ID");
          info.userName = rs.getString("userName");
          info.Name = rs.getString("User_Name");
          info.Password = rs.getString("passWord");
          info.isAdmin = rs.getBoolean("Admin");
          return true;
      }
      return false;
  }
  </code></pre>
  
  <p>}</p>