Why I get NullPointerException? [закрыт]

This is my backend method:

String sql = "SELECT BR.ID, BR.BORROWER_NAME, BK.BOOK_NAME, BK.AUTHOR,BR.WHEN_BORROWED FROM BORROWERS BR\n" + "INNER JOIN BOOKS BK ON BR.BOOKS_ID = BK.ID\n" + "WHERE BR.ACTIVE = 1 AND BK.ACTIVE = 1";

    try {
        c = DBHelper.getConnection();
        if (c != null) {
            ps = c.prepareStatement(sql);
            rs = ps.executeQuery();
            while (rs.next()) {
                Borrowers borrower = new Borrowers();
                Books book = new Books();
                borrower.setId(rs.getLong("ID"));
                borrower.setBorrowerName(rs.getString("BORROWER_NAME"));
                book.setBookName(rs.getString("BOOK_NAME"));
                book.setAuthor(rs.getNString("AUTHOR"));
                borrower.setWhenBorrowed(rs.getDate("WHEN_BORROWED"));
                borrower.setBook(book);
                borrowersList.add(borrower);
            }

And this is JFrame method for library project. It shows NullPointerException in the for each row:

       jTable1.setModel(model);
        model.addColumn("No");
        model.addColumn("Borrower");
        model.addColumn("Book");
        model.addColumn("Author");
        model.addColumn("When Borrowed");
        for (Borrowers borrowers : borrowersList) {
            Object[] data = new Object[]{
                borrowers.getId(), borrowers.getBorrowerName(), borrowers.getBook().getBookName(), borrowers.getBook().getAuthor(),
                borrowers.getWhenBorrowed()
            };
            model.addRow(data);
        }
        model.fireTableDataChanged();