public boolean acceptReturn(String ISBN)
    {
        try
        {
            Statement statementTitleISBN = connection.createStatement();
            ResultSet isbnFromTitles = statementTitleISBN.executeQuery("SELECT ISBN FROM Titles");

            Statement statementISBN = connection.createStatement();
            ResultSet isbnFromCheckedOut = statementISBN.executeQuery("SELECT ISBN FROM Checkedout");

            ArrayList<String> isbnFromTitlesArrayList = new ArrayList<String>();
            ArrayList<String> isbnFromCheckedOutArrayList = new ArrayList<String>();

            while(isbnFromTitles.next())
            {
                isbnFromTitlesArrayList.add(isbnFromTitles.getString("ISBN").toLowerCase().trim());
            }

            while(isbnFromCheckedOut.next())
            {
                isbnFromCheckedOutArrayList.add(isbnFromCheckedOut.getString("ISBN").toLowerCase().trim());
            }
             if (isbnFromCheckedOutArrayList.contains(ISBN.toLowerCase().trim()))
            {
                preparedStatement = connection.prepareStatement("DELETE FROM CheckedOut WHERE ISBN = ?");
                preparedStatement.setString(1, ISBN);
                preparedStatement.executeUpdate();
                setQuery("SELECT * FROM CheckedOut");
                return true;
            }
             else if (!isbnFromCheckedOutArrayList.contains(ISBN.toLowerCase().trim()))
             {
                 JOptionPane.showMessageDialog(null, "Book has already been returned", "Error", JOptionPane.ERROR_MESSAGE);
                 return false;
             }
             else if (!isbnFromTitlesArrayList.contains(ISBN.toLowerCase().trim()))
             {
                 JOptionPane.showMessageDialog(null, "Book not found", "Error", JOptionPane.ERROR_MESSAGE);
                 return false;
             }
             return false;
        } catch (SQLException sqlException)
        {
            sqlException.printStackTrace();
            close();
            return false;
        }
    }