Java fila NIO.2

Question 1

How do you get an attribute of a file?

Answer 1

Object object = Files.getAttribute(path, “creationTime”,

LinkOption.NOFOLLOW_LINKS);

Question 2

What is the difference between File and Files?

Answer 2

File is an old class (java 4) that represents file/directory path names, whereas Files was introduced in java 7 as a utility class with comprehensive support for IO APIs

Question 3

What is the difference between Path and Paths?

Answer 3

The path interface represents a file/directory path and defines a useful list of methods. Paths is a utility class that offers only two methods ( both to get the path object)

Question 4

What is the Files.lines() used for?

Answer 4

Read contents of a file

Question 5

What is a Path?

Answer 5

Programming abstraction to represent the path of a file/directory

Question 6

How do you get the instance of a path?

Answer 6

using the get() method of the Paths class

Question 7

What does the Files.list(Path path) method returns?

Answer 7

Stream{Path}

It is like a walk() method with dept limit to 1, it is analogous to File.listFiles()

Question 8

What does the Files.walk(Path path) method return?

Answer 8

Stream{Path}. It will not traverse symbolic links by default

Question 9

What is the difference between Files.list() and Files.walk()?

Answer 9

.list() does not recursively traverse the directories while .walk() does

Question 10

What does the Files.lines() returns?

Answer 10

Stream{Lines}

Question 11

Given:

File file = new File(“x”);

how can you get a instance of Path?

Answer 11

file.toPath();

Question 12

What are the common optional arguments in NIO2 and its usages?

Answer 12

EnumValue:Usage

• NOFOLLOW_LINKS : test file exists, read file data, copy, move file
• FOLLOW_LINKS : transverse a directory tree
• COPY_ATTRIBUTES : copy file
• REPLACE_EXISTING: copy file/ move file
• ATOMIC_MOVE: move file

Question 13

What does the toAbsolutePath() does?

Answer 13

Returns the absolute path of this path. If the path is already absolute, then it just returns it

Question 14

What does the relativize(String other) method do?

Answer 14

constructs a relative path between the path and the given path.

• It requires that both paths be absolute or both relative, or else it will throw a new IllegalArgumentException
• If this path and the given path are equal then an empty path is returned
• A relative path cannot be constructed if only one of the paths have a root component.
• Where both paths have a root component then it is implementation dependent if a relative path can be constructed.

Question 15

What does the resolve(Path path)

resolve(String string) method do?

Answer 15

• adds two paths
• if the other is a absolute path, just returns other
• if the other path is empty, just return THIS path
• where the given path has a root component then resolution is highly implementation dependent and therefore unspecified.

Question 16

True or false?

Files belong to java.io while File belong to NIO2?

Answer 16

False,

File belongs to legacy java.io while Files belong to the NIO2

Question 17

What does the Files.move(Path path, Path path) do?

Answer 17

moves or renames a file, throws IOException

Question 18

What does the Files.delete(Path path) do?

Answer 18

deles a file or EMPTY directory within the file system. It throws IOException under a variety of circumstances
(if it is a non empty directory)

Question 19

What does the Files.readAllLines(Path path, ?Charset) return?

Answer 19

reads the lines of a text file and returns the results as an ordered List of String. Throws IOException, can pass an option charset param

Question 20

Regarding to file attributes…

what is a view?

Answer 20

A view is a group of related attributes for a particular file system type

Question 21

What does the Files.readAttributes(Path path, Class{a}, LinkOption options) returns?

Answer 21

returns a read only view of the file attributes. May throw Exception

Question 22

What does the

Files.getFileAttributeView(Path path,Class type, LinkOption… options) return?

Answer 22

return the underlying attribute view and it provides a direct resource for modifying file information. May throw Exception

Question 23

What are the attributes and view classes?

Answer 23

Attributes class: View class

BasicFileAttributes: BasicFileAttributeView

DosFileAttributes:DosFileAttributeview

PosixFileAttributes: PosixFileAttributeView

Question 24

What does the Files.find(Path, int, Bipredicate) does?

Answer 24

behaves in a similar maner as the Files.walk(). Returns a Stream{Path}

Question 25

Given the path:

/zoo/animals/bear/koala/food.text

what does

a) path.subPath(1,3)
b) path.subPath(1,2)
c) path.subPath(0,1)

returns?

Answer 25

a) animals/bear
b) animals
c) zoo

Question 26

What are some key points regarding Path.getName(int index)

Answer 26

1. Indices for path name start from 0
2. root (ie: c:) is not included in the path names
3. \ is not a part of a pathName
4. if you pass a negative index or a value greater than or equal to the number of elements, or this path has zero name elements, java will throw java.lang.IllegalException