Count all the words in a file using java Streams

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I was trying to count the number of unique words in a text file. For the sake of simplicity, my current file content is:

This is a sample file

My attempt is:

long wordCount = 
    Files.lines(Paths.get("sample.txt"))
         .map(line -> line.split("\\s+"))
         .distinct()
         .count();
System.out.println(wordCount);

This compiles and runs fine, but results in 1, while it should be 5.

distinct-values java-stream java-8 word java
2 Answers

You are mapping each line to an array (transforming a Stream<String> to a Stream<String[]>, and then count the number of array elements (i.e. the number of lines in the file).

You should use flatMap to create a Stream<String> of all the words in the file, and after the distinct() and count() operations, you'll get the number of distinct words.

long wordCount = 
    Files.lines(Paths.get("sample.txt"))
         .flatMap(line -> Arrays.stream(line.split("\\s+")))
         .distinct()
         .count();
user_12215710

You seem to be counting the lines in your file instead :

map(line -> line.split("\\s+")) // this is a Stream<String[]>

You shall further use Stream.flatMap as:

long wordCount = Files.lines(Paths.get("sample.txt"))
        .map(line -> line.split("\\s+"))
        .flatMap(Arrays::stream)
        .distinct()
        .count();
user_17461180
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