Java™ How To Program (Early Objects), Tenth Edition

Section 17.7 Creating a Stream<String> from a File

• Files method lines creates a Stream<String> for reading the lines of text from a file.

• Stream method flatMap (p. 760) receives a Function that maps an object into a stream—e.g., a line of text into words.

• Pattern method splitAsStream (p. 760) uses a regular expression to tokenize a String.

• Collectors method groupingBy with three arguments receives a classifier, a Map factory and a downstream Collector. The classifier is a Function that returns objects which are used as keys in the resulting Map. The Map factory is an object that implements interface Supplier and returns a new Map collection. The downstream Collector determines how to collect each group’s elements.

• Map method entrySet ...