1Z0-819 I/O Operations 2

Question 1

Which method in the `Files` class copies a file and replaces the destination if it already exists?

Accepted Answer

Files.copy(src, dst, StandardCopyOption.REPLACE_EXISTING)

Answer

`Files.copy` with `StandardCopyOption.REPLACE_EXISTING` overwrites the destination file if it exists.

Question 2

What does `Files.walk(path)` return?

Accepted Answer

A `Stream<Path>` of all files in the directory tree

Answer

`Files.walk` returns a lazy `Stream<Path>` that traverses the directory tree depth-first.

Question 3

Which `OpenOption` must be specified to append to an existing file using `Files.newOutputStream`?

Accepted Answer

StandardOpenOption.APPEND

Answer

`StandardOpenOption.APPEND` positions the stream at the end of the file before each write.

Question 4

What exception is thrown when you call `Files.readAllBytes` on a path that does not exist?

Accepted Answer

NoSuchFileException

Answer

`Files.readAllBytes` throws `NoSuchFileException` (a subclass of `IOException`) when the file is absent.

Question 5

What is the result of `Path.relativize(other)` when `other` is not relative to the base path?

Accepted Answer

It may include `..` segments to navigate up the tree

Answer

`relativize` uses `..` components to express a path from base to target even when traversal above base is needed.

(1Z0-819) Oracle Java SE 11 Developer Practice Test