How to copy or move a file

Short answer

Suppose there is a file photo.jpg. Files.copy() copies it, Files.move() moves or renames it:

void main() throws IOException {
    Files.copy(Path.of("photo.jpg"), Path.of("photo-backup.jpg"));
    Files.move(Path.of("photo.jpg"), Path.of("holiday.jpg"));
 
    IO.println(Files.exists(Path.of("photo.jpg")));
    IO.println(Files.exists(Path.of("photo-backup.jpg")));
    IO.println(Files.exists(Path.of("holiday.jpg")));
}

Output:

false
true
true

Overwriting an existing file

By default copying onto an existing file throws. The REPLACE_EXISTING option allows overwriting:

void main() throws IOException {
    Files.writeString(Path.of("backup.jpg"), "old");
    Files.copy(Path.of("photo.jpg"), Path.of("backup.jpg"), StandardCopyOption.REPLACE_EXISTING);
 
    IO.print(Files.readString(Path.of("backup.jpg")));
}

Output:

image data

Into another folder

resolve() appends a file name to a folder path:

void main() throws IOException {
    Path source = Path.of("photo.jpg");
    Path archive = Files.createDirectories(Path.of("archive"));
 
    Path target = Files.move(source, archive.resolve(source.getFileName()));
    IO.println(target.toString().replace('\\', '/'));
}

Output:

archive/photo.jpg

Common mistake

Copying without the option when the target file already exists:

void main() throws IOException {
    Files.writeString(Path.of("backup.jpg"), "old");
    Files.copy(Path.of("photo.jpg"), Path.of("backup.jpg"));
}

Output:

Exception in thread "main" java.nio.file.FileAlreadyExistsException: backup.jpg

Thanks for reading!

Short answer

Overwriting an existing file

Into another folder

Common mistake

Functions used in this recipe

Thanks for reading!