word_freq.java in Java

The word-count CLI in Java: read a file, tally a map, print a top ten.

// word_freq: count word frequencies in a file, print the top ten
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.HashMap;
import java.util.Map;

class WordFreq {
    public static void main(String[] args) throws Exception {
        if (args.length != 1) {
            System.err.println("usage: word_freq <file>");
            System.exit(1);
        }

        var counts = new HashMap<String, Integer>();
        for (var line : Files.readAllLines(Path.of(args[0]))) {
            for (var word : line.toLowerCase().split("[^a-z']+")) {
                if (!word.isEmpty()) {
                    counts.merge(word, 1, Integer::sum);
                }
            }
        }

        System.out.println(counts.size() + " distinct words");
        counts.entrySet().stream()
            .sorted(Map.Entry.<String, Integer>comparingByValue()
                .reversed())
            .limit(10)
            .forEach(e -> System.out.printf("%5d  %s%n",
                                            e.getValue(), e.getKey()));
    }
}

How it works

1. args carries the command line; bad usage exits with code 1.
2. merge with Integer::sum makes the tally one line.
3. A stream sorts the entries by count and formats the report.

Keywords and builtins used here

• WordFreq
• class
• for
• if
• main
• new
• public
• static
• throws
• var
• void

The run, in numbers

Lines

31

Characters to type

795

Tokens

221

Three-star pace

90 tpm

At the three-star pace of 90 tokens a minute, this run takes about 147 seconds.

Type this snippet

Step 1 of 2 in Encore, step 28 of 29 in Language basics.

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