StreamStudy.java

package nextstep.fp;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class StreamStudy {
    public static long countWords() throws IOException {
        String contents = new String(Files.readAllBytes(Paths
                                                            .get("src/main/resources/fp/war-and-peace.txt")), StandardCharsets.UTF_8);
        List<String> words = Arrays.asList(contents.split("[\\P{L}]+"));
        return words.stream()
                    .filter(word -> word.length() > 12)
                    .count();
    }

    public static void printLongestWordTop100() throws IOException {
        String contents = new String(Files.readAllBytes(Paths
                                                            .get("src/main/resources/fp/war-and-peace.txt")), StandardCharsets.UTF_8);
        List<String> words = Arrays.asList(contents.split("[\\P{L}]+"));
        String joinWords = words.stream()
                              .filter(word -> word.length() > 12)
                              .distinct()
                              .sorted((p1, p2) -> Integer.compare(p2.length(), p1.length()))
                              .limit(100)
                              .map(String::toLowerCase)
                              .collect(Collectors.joining("\n"));

        System.out.println(joinWords);
    }

    public static List<Integer> doubleNumbers(List<Integer> numbers) {
        return numbers.stream()
                      .map(x -> 2 * x)
                      .collect(Collectors.toList());
    }

    public static long sumAll(List<Integer> numbers) {
        return numbers.stream()
                      .reduce(0, (x, y) -> x + y);
    }

    public static long sumOverThreeAndDouble(List<Integer> numbers) {
        return numbers.stream()
                      .filter(number -> number > 3)
                      .mapToInt(number -> number * 2)
                      .sum();
    }
}