The Files Class

Files — high-level operations around Path

Path describes a path, while the Files class performs operations on that path: it creates files and directories, reads and writes data, copies, moves, deletes, and obtains file-system properties. It is a set of static methods, so there is no need to create a Files object.

Path path = Path.of("notes.txt");

Files.writeString(path, "Hello", StandardCharsets.UTF_8);
String text = Files.readString(path, StandardCharsets.UTF_8);

For a small text file, methods like these are often simpler than manually assembling a reader/writer chain. But convenience does not remove the question of size: methods that return the whole file as one string or array load all of its contents into memory.

Directories, copying, and moving

Path source = Path.of("data", "report.txt");
Path backup = Path.of("backup", "report.txt");

Files.createDirectories(backup.getParent());
Files.copy(source, backup);

createDirectories() creates missing directories along the path and does not require each parent to be created with a separate call. For copying and moving, behavior when the target file already exists is configured with options, such as StandardCopyOption.REPLACE_EXISTING.

Checks and metadata

Through Files, you can check a path's type and read file properties: for example isDirectory(), isRegularFile(), size(), and the last-modified time. However, the state of the file system can change between a check and the next operation.

Methods that return a Stream

Some operations, such as Files.list() and Files.lines(), return a Stream connected to an open file-system resource. That stream must be closed after use.

try (Stream<Path> entries = Files.list(Path.of("data"))) {
    entries.forEach(System.out::println);
}