16. Input/Output (IO)

16.1. Writing to a file

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.util.Arrays;
import java.util.List;

List<String> names = Arrays.asList("John", "Jack", "Jane", "Joyce");

try (var writer = new BufferedWriter(new FileWriter(new File("test.txt")))) {
  for (var name : names) {
    writer.write(name);
    writer.write('\n');
  }
}

16.2. Reading from a file

16.2.1. Reading one line at a time

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;

try (var reader = new BufferedReader(new FileReader(new File("test.txt")))) {
  String line = null;
  while ((line = reader.readLine()) != null) {
    System.out.println(line);
  }
}

16.2.2. Reading all lines

import java.nio.file.Files;
import java.nio.file.Paths;

for (var line : Files.readAllLines(Paths.get("test.txt"))) {
  System.out.println(line);
}

16.2.3. Reading whole file

import java.nio.file.Files;
import java.nio.file.Paths;

String text = new String(
    Files.readAllBytes(
        Paths.get("test.txt")));

System.out.println(text);