Java Database Connectivity (JDBC)

I can't get my delete method to work:

// delete book
 	public void deleteBook(String isbn)
 	{
 		boolean deleted = false;
 		
 		try
 		{
 			doStatementQuery(bookSQLStatements.RemoveBook(isbn), 3, 1);
 			statement.close();
 			bookSQLStatements.CloseDatabase();
 			deleted = true;
 		}
 		catch(SQLException sqlException)
 		{
 			System.out.println(sqlException.toString());
 			deleted = false;
 		}
 		
 		if(deleted)
 		{
 			JOptionPane.showMessageDialog(null, "Book Details Relating to: " + isbn + " have been deleted", "Deletion Confirmation", 1);
 		}
 		else
 		{
 			JOptionPane.showMessageDialog(null, "It has not been possible to delete Book Details relating to: " + isbn + "!", "Deletion Confirmation", 1);
 		}
 	}
 	
 	// this method creates a statement from the query passed as an argument
 	private void doStatementQuery(String query, int execute, int connect)
 	{
 		int result = 0;
 		resultSet = null;
 		statement = null;
 		connection = null;
 		
 		switch(connect)
 		{
 			case 1: connection = bookSQLStatements.OpenDatabase();
 			break;
 		}
 		
 		try
 		{
 			statement = connection.createStatement();
 			System.out.println(query);
 			
 			if(execute == 1)
 			{
 				resultSet = statement.executeQuery(query);	
 			} 	
 			
 			else if(execute == 2)
 			{
 				result = statement.executeUpdate(query);
 			}		
 			
 			else if (execute == 3) 
 			{ 
				statement.execute(query);
			}
		}
 		catch(SQLException sqle)
 		{
 			System.out.println(sqle.toString());
 		}
 	}

// method to remove a book from the database
 	public String RemoveBook(String isbnIn)
 	{
 		return "DELETE FROM Book WHERE ISBN = '" + isbnIn + "'";
 	}

is about all of the methods that it relates to, it's not throwing an error but it's also not working. Thank you for any help that you can give, Wonkey