List question

[John Olivas]

My question is why do I throw an exception every time I try to add data to my List?

method below, thanks!

private List<String> submitSqlStatementToDatabase(String SqlStatement, Connection connection) {

        Statement statement = null; // query statement object
        ResultSet resultSet = null; // manages results object
        List <String>result = null; // return data

        // try catch is task #6
        try {

            // Creates a Statement object for sending SQL statements to the database.
            statement = connection.createStatement();

            // send the query (statment method execute query)
            resultSet = statement.executeQuery(SqlStatement);

            // Retrieves the number, types and properties of this ResultSet object's columns.
            ResultSetMetaData metaData = resultSet.getMetaData();

            // Returns the number of columns in this ResultSet object.
            int numberOfColumns = metaData.getColumnCount();

            // for each column in the table loop and print out the column name
            //StringBuilder sb = new StringBuilder("");
            for (int i = 1; i <= numberOfColumns; i++) {
                System.out.printf("%-8s\t", metaData.getColumnName(i));
                result.add(resultSet.getString(i));
            }
            System.out.println();
            // add the column names to the result

            // Moves the cursor froward one row from its current position.
            while (resultSet.next()) {
                for (int i = 1; i <= numberOfColumns; i++) {
                    System.out.printf("%-8s\t", resultSet.getObject(i));
                    result.add(resultSet.getString(i));
                    //sb.append(resultSet.getObject(i));
                    //sb.append("\t");
                }
                System.out.println();
                //sb.append("\n");
                // TODO add the table rows to the result
                //String text = sb.toString();
                //result.add(text);
            }
        } catch (SQLException e) {
            System.err.println("SQL statement failed with " + e.getMessage());
        }

        return result;
    }

[pete stein]

You need to show the exact expression information that is returned and indicate which line is throwing it to get better help. So for now I can only guess that you're getting a NullPointerException as you never initialize the result List<String>.

For instance, I would change this:

List <String>result = null; // List is null  

to this:

List <String> result = new ArrayList<String>(); // List now initialized

ps: I added code tags to your post to help make it readable. The forum FAQ's will show you how to do this yourself: UseCodeTags

ps2: Please let me be the first to welcome you to JavaRanch!

[David Newton]

(And make sure you close the connection, and don't over-comment.)

[John Olivas]

Thank you both. I will add the code tags and remove the excess comments before posting.

And yes you were correct, initializing the List did the trick.