Here’s another neat streams snippet, which in three lines handles what would take at least two loops in pre-Java 8 code. The task at hand is to count the number of occurrences of each unique word in a file. Given the content shown below, this Bash command line would solve it.
The Java code follows a similar flow as seen in the pipes above: Read the file, split each line by space, and flatten the result from all lines into a single stream. Finally, the collect() function is used with the groupingBy() helper, to map each token (or word) in the stream (the identity) to its count.
The Java map will contain the following key-value pairs. Here, the words are also accidentally sorted alphabetically. However, the order is not guaranteed by collect() function, since it returns a HashMap.