JDBC returning empty result set

I figured it out....stupid Oracle didn't like the number of concurrent connections I had (all two of them, one for console, one for java). Unfortunately, the server is not under my control so I will just have to deal with it. You would think that Oracle would provide a better response. Instead it just returned empty result sets.

Thanks for the responses

edit Since this was asked/answered there have been a number of people pointed out that the underlying cause is more likely related to the commit/transaction settings in use. Please be sure to see other answers for additional hints and possible solutions.

I see a few pitfalls in your code, there are a few places where things can go wrong:

First, use of regular statements. Use prepared statements so you won't have problems with SQL injection.

Instead of

statement = connection.createStatement();

use

statement = connection.prepareStatement(String sql);

With this, your query becomes

"select distinct group_name From group_members where username= ?"

and you set username with

 statement.setString(1, username);

Next, I don't like use of your myDB class. What if results is null? You're not doing any error checking for that in your public List<InterestGroup> getGroups() method.

public void sendQuery(String query) seems to me like it shouldn't be void, but it should return a ResultSet. Also, search on the net for proper ways to do JDBC exception handling.

Also, this line:

new InterestGroup(results.getString("group_name"), myDB)

Why do you have myDB as a parameter?

I'd suggest adding more System.out.println statements in your code so you can see where things can go wrong.