Java 8 Stream API Sample

• 2018/03/30

Sample code

I tried reading and writing files with the Stream API that shipped with Java 8.

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Stream;

/**
 * Stream sample
 * The character set is fixed to UTF-8 (Shift_JIS cannot be used).
 */
public class SampleStream {
	/** Read path */
	private static final String INPUT_PATH = "C:\\temp\\in.txt";
	/** Write path */
	private static final String OUTPUT_PATH = "C:\\temp\\out.txt";

	public static void main(String[] args) throws Exception {
		// Obtain the FileSystem
		FileSystem fs = FileSystems.getDefault();
		// Path to the source file
		Path path = fs.getPath(INPUT_PATH);
		// Path to the output file
		Path out = fs.getPath(OUTPUT_PATH);

		// Read pattern #1: use Files.lines
		try (Stream<String> stream = Files.lines(path, StandardCharsets.UTF_8)) {
			stream.filter(s -> s.contains("link"))
					.map(s -> s.replace("html", "form"))
					.map(s -> s.replace("action", "href"))
					.forEach(System.out::println);
		} catch (IOException e) {
			System.out.println("error");
		}

		// Read pattern #2: use Files.readAllLines
		List<String> lines = Files.readAllLines(path, StandardCharsets.UTF_8);
		List<String> output = new ArrayList<String>();
		lines.stream().filter(s -> s.contains("link")).forEach(output::add);

		// Write the extracted data to a text file
		Files.write(out, output, StandardCharsets.UTF_8, StandardOpenOption.APPEND);

		// Print the output to verify it
		for (String put : output) {
			System.out.println(put);
		}
	}

}

• Apparently UTF-8 is the only supported encoding; trying Shift_JIS throws an exception.