Abstraction is necessary, but I think OOP as practiced in many companies likes abstraction a bit too much. At the extreme people treat everything except the co

Abstraction is necessary, but I think OOP as practiced in many companies likes abstraction a bit too much. At the extreme people treat everything except the code they currently work on as black boxes and code like this is written: //this was written long ago in one class List<Book> getBooks(BookRepository bookRepository, String author) { var books = bookRepository.getBooksByAuthor(author); if (books.isEmpty()) return null; return books; } //this too but in a different task and in a different class Collection<Book> getBookAboutKeyword(String author, String keyword) { var books = getBooks(this.bookRepo, author); if (books == null) { return null; } // let's ignore the fact this should use filtering on db return books.stream().filter(Book b -> b.about(keyword)).collect(Collections::toList()); } //this is written now and there's a NPE List<Book> getBooksAndFooBarThem(List<Books> books, String author, String keyword) { var books = getBookAboutKeyword(books, author, keyword); //foobar them return books; } And of course the solution to NPE was to put ANOTHER null check in the getBooksAndFooBarThem function because anything up or down the callstack is black magic.