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 ...
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