java内存管理的问题（代码效率）

下面的两段代码在查询大容量表的时候，会有效率上的差距吗？
第二种方法有没有可能造成栈溢出问题呢
代码片段一
stmt = con.prepareStatement(sql);
stmt.setInt(1, category.getId());
rs = stmt.executeQuery();
Book book = null;
while(rs.next()){
book = new Book();
book.setAuthor(rs.getString("author"));
book.setAuthorSummary(rs.getString("author_summary"));
book.setAddTime(rs.getLong("add_time"));
book.setDangPrice(rs.getDouble("dang_price"));
book.setFixedPrice(rs.getDouble("fixed_price"));
book.setCatalogue(rs.getString("catalogue"));
book.setPrintTime(rs.getLong("publish_time"));
book.setPublishing(rs.getString("publishing"));
book.setProductName(rs.getString("product_name"));
books.add(book);
}
代码片段二
stmt = con.prepareStatement(sql);
stmt.setInt(1, category.getId());
rs = stmt.executeQuery();
while(rs.next()){
Bookbook = new Book();
book.setAuthor(rs.getString("author"));
book.setAuthorSummary(rs.getString("author_summary"));
book.setAddTime(rs.getLong("add_time"));
book.setDangPrice(rs.getDouble("dang_price"));
book.setFixedPrice(rs.getDouble("fixed_price"));
book.setCatalogue(rs.getString("catalogue"));
book.setPrintTime(rs.getLong("publish_time"));
book.setPublishing(rs.getString("publishing"));
book.setProductName(rs.getString("product_name"));
books.add(book);
}