A higher-order function is a function or method that accepts functions as arguments, returns a function, or both. In Java streams, map and filter accept function-valued arguments: map transforms elements, while filter decides which elements remain. section 6.3.1
Turn a book pipeline into a readable transformation
A verbose approach can separate the operations and increase the reader’s jumping between declarations. A compact pipeline keeps the story in order: books.stream().filter(book -> book.publishedDate().isAfter(LocalDate.now().minusYears(1))).map(Book::author).toList(). The filter keeps recent books; map transforms each remaining Book into its author name. section 6.3.1
Chaining higher-order methods creates transformation stages that read from top to bottom. The pipeline remains lazy, so author extraction does not occur until a terminal operation requests the result. For short, one-shot operations, inline lambdas or method references usually keep the transformation easier to follow; avoid multiline lambda blocks when they obscure the pipeline. section 6.3.1
