Parses a list of words, sorts lexicographically, and groups words that are anagrams. Today I learned how to use the streams API and the word "lexicographic".

AnagramFinder.java

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class AnagramFinder {

    public static void parseAnagrams(Stream<String> inStream, Writer pw) {
        inStream
                .sorted() // Sort input words lexicographically
                .collect(Collectors.groupingBy(word -> Stream.of(word // GroupBy -> Map of key<String> value<List> pairs
                        .split("")) // Split word into Array of chars
                        .sorted() // Sort array of chars
                        .collect(Collectors.joining()))) //Map key -> sortedString | value -> List of anagrams
                .forEach((key, value) -> { // for each (key, value) pair in the Hash Map...
                    try {
                        pw.append(value.stream() //join value<list> eleements, with "," separator, write out
                                .collect(Collectors.joining(",")))
                                .append("\n");  //Add \n after every (key, value) pair. 
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                });
    }

    public static void main(String[] args) {
        String pathToCSV = "/home/bryce/Workspace/MENG/anagrams-finder/src/com/company/";
        String fileName = "words.csv";
        String outputFileName = "output.csv";
        
        try ( //Try-with-resource: Closes all resources that implement AutoClosable feature
                PrintWriter pw = new PrintWriter(new File(pathToCSV + outputFileName));
                Stream<String> inStream = Files.lines(Paths.get(pathToCSV.concat(fileName)));
        ) {
            parseAnagrams(inStream, pw);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

AnagramFinderTest.java

import java.io.StringWriter;
import java.util.Arrays;
import java.util.stream.Stream;

import static com.company.AnagramFinder.parseAnagrams;
import static org.junit.jupiter.api.Assertions.*;

class AnagramFinderTest {

    @org.junit.jupiter.api.Test
    void testParseAnagrams() {
        Stream<String> inStream = Arrays.stream(new String[]
                {
                        "car",
                        "dog",
                        "bed",
                        "stop",
                        "god",
                        "pots",
                        "arc",
                        "tops"
                });

        String expected =
                "arc,car\n" +
                "bed\n" +
                "pots,stop,tops\n" +
                "dog,god\n";

        StringWriter stringWriter = new StringWriter();
        parseAnagrams(inStream, stringWriter);
        assertEquals(expected, stringWriter.toString());
    }
}