Java and SQLite: Throwing ResultSet closed but proceeding

Question

I've got a following problem: I'm trying to insert data (in this case a username) into a table using the following code:

void AddNewUser(String name, Connection conn){

    if(ret == null){
        ret = new DB_Retriever(conn);
    }

    if(!ret.UserExists(name, conn)){
        try{
            Statement stm = conn.createStatement();
            stm.executeUpdate(DB_OperationalData.insert_new_user[0][0] + name + DB_OperationalData.insert_new_user[0][1]);
            stm.executeUpdate(DB_OperationalData.insert_new_user[1][0] + name + DB_OperationalData.insert_new_user[1][1]);
            stm.close();
        }
        catch(SQLException e){
            e.printStackTrace();
        }
    }
}

By the way: It absolutely doesn't matter what I put in the catch clause, nothing that I put there is executed. Just to make everything clear, here is the content of the DB_OperationalData.insert_new_user String array:

public static final String[][] insert_new_user = {
    {"INSERT INTO User (Username, Status) VALUES ('","','IN');"},
    {"INSERT INTO Statistics (Player_ID) SELECT ID FROM User WHERE Username='","';"}};

The second statement is supposed to copy the ID of the user that is inserted and put it into Player_ID field of the Statistics table (Table User's ID is an autonumbered field).

The exception I get is:

Error while processing the query: java.sql.SQLException: ResultSet closed

What is interesting, is that it works and the data is added correctly but I simply do not want any exceptions thrown.

That's the console output I get:

This is 'data' Package Testing class
Connection to the database established.
The number of tables existing in the database is: 0
All the queries have been processed successfully
Adding new users: 
Error while processing the query: java.sql.SQLException: ResultSet closed

All the lines above the Exception are my own printouts, so I know what has actually happened.

[EDIT]

I have changed the code to use the PreparedStatement instead of ordinary Statement and the current try clause looks as follows:

PreparedStatement pstm = conn.prepareStatement(DB_OperationalData.insert_new_user[0]);
pstm.setString(1, name);
pstm.addBatch();
conn.setAutoCommit(false);
pstm.executeBatch();
conn.setAutoCommit(true);
pstm.close();

And the output is (still regardless of the contents of the catch clause):

This is 'data' Package Testing class
Connection to the database established.
The number of tables existing in the database is: 0
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at org.sqlite.PrepStmt.batch(PrepStmt.java:173)
at org.sqlite.PrepStmt.setString(PrepStmt.java:254)
at data.DB_Writer.AddNewUser(DB_Writer.java:28)
at data.DataHandler.AddNewUser(DataHandler.java:94)
at data.Tester.main(Tester.java:18)
All the queries have been processed successfully
Adding new users: 
Error while processing the query: java.sql.SQLException: ResultSet closed

[EDIT 2] With regards to the original version, when I remove the stm.close(); there is absolutely no difference and I still get the 'ResultSet closed' Exception.

[EDIT 3] Here is the code of the method that is calling the above:

public void AddNewUser(String username)throws IllegalUsernameException{
    if(username.length()==0 || username.length()>20){
        throw new IllegalUsernameException();
    }
    writer.AddNewUser(username, conn);

}

The connection to the database is established by this class:

class DB_Connection {


public static Connection getConnection(){
    Connection conn = null;

    try{
        Class.forName("org.sqlite.JDBC");
    }
    catch(ClassNotFoundException e){
        log("Error while loading the database driver: " + e);
        return null;
    }
    try{
        conn = DriverManager.getConnection("jdbc:sqlite:database.db");
    }
    catch(SQLException e){
        log("Unable to connect to the database: " + e);
        return null;
    }
    return conn;
}

public static void log(String msg){
    System.out.println(msg);
}

}

The DB_Retriever's method that is checking for the existing username:

boolean UserExists(String name, Connection conn){

    String result = "";

    try{
        Statement stm = conn.createStatement();
        ResultSet rs = stm.executeQuery(DB_OperationalData.user_exists[0] + name + DB_OperationalData.user_exists[1]);
        result = rs.getString("Username");
    }
    catch(SQLException e){
        System.out.println("Error while processing the query: " + e);
    }

    if(result.equals(name)){
        return true;
    }

    return false;
}

Answer 1

The only location where Error while processing the query: java.sql.SQLException: ResultSet closed could be printed to the console is in UserExists(..), unless there is another method with a similar catch block. Indeed the ResultSet is not used correctly in UserExists, what may cause the error.

For a more complete description of how to work with JDBC look at this answer or the JDBC documentation. A possible alternative to the existing UserExists is:

boolean userExists(String name, Connection conn) {
   PreparedStatement stmt = null;
   try{
      stmt = conn.prepareStatement("SELECT COUNT(Username) FROM User WHERE Username = ?");
      stmt.setString(1, name);
      ResultSet rs = stmt.executeQuery();
      rs.next();  // set cursor to first row
      int count = rs.getInt(1);
      rs.close();
      return count > 0;
   } catch(SQLException e) {
      // propagate error
      throw new RuntimeException(e);
   } finally {
      // clean up resources
      if (stmt != null) {
        try {
           stmt.close();
        } catch (SQLException ignore) {
           log("error on sql clean up", ignore);
        }
      }
   }
}