b2-c09

Question 1

Name the five key interfaces of JDBC

Answer 1

Driver: Establishes a connection to the database
Connection: Sends commands to a database
PreparedStatement: Executes a SQL query
CallableStatement: Executes commands stored in the database
ResultSet: Reads results of a query

Question 2

What does the NIO.2 acronym stand for?

Answer 2

The second version of the Non-blocking Input/Output API. It is sometimes referred to as the “New I/O.”

Question 3

Which legacy class is NIO.2 / java.nio.file.Path is intended to replace?

Answer 3

java.io.File

Question 4

What are the similarities between java.nio.file.Path and java.io.File?

Answer 4

1. Both may refer to an absolute path or relative path within the file system.
2. Both may refer to a file or a directory.

Question 5

What are the differences between java.nio.file.Path and java.io.File?

Answer 5

Unlike the java.io.File class, the Path interface contains support for creating, detecting, and navigating symbolic link.

Question 6

What is symbolic link?

Answer 6

A symbolic link is a special file within a file system that serves as a reference or pointer to another file or directory

Question 7

In general, symbolic links are transparent to the user, as the operating system takes care of resolving the reference to the actual file.

True/False

Answer 7

True

Question 8

What is the rationale for making Path an interface as opposed to a class

Answer 8

When a Path is created, the JVM returns a file system–specific implementation, such as a Windows or Unix Path class.

Question 9

List six ways to create Path object

Answer 9

With/from:

1. Path interface - Path.of()
2. Paths class - Paths.get()
3. URI class
4. FileSystem class
5. java.io.File class
6. String values

Question 10

The simplest and most straightforward way to obtain a Path object is to use ________________________________________________________.

Answer 10

the static factory method defined within the Path interface.

public static Path of(String first, String… more)

Question 11

Describe absolute path and relative path

Answer 11

• if path starts with / it is absolute (Unix)
• if path starts with a drive letter (c:), it is absolute (Windows)
• otherwise, it is relative

Question 12

Path.of() can take a varargs besides a connected string of path elements. What is the benefit of this capability?

Answer 12

The advantage of the varargs is that it is more robust, as it inserts the proper operating system path separator for you.

Question 13

Describe Path.of()

Answer 13

-a static method defined in Path interface

-Path factory method
public static Path of(String first, String… more)

Question 14

How can a Path object be constructed from String values?

Answer 14

Relative

Path path1 = Path.of(“pandas/cuddly.png”);

Absolute -Windows

Path path2 = Path.of(“c:\zooinfo\November\employees.txt”);

Absolute - Unix

Path path3 = Path.of(“/home/zoodirectory

Question 15

What parameters types does Path.of() take?

Answer 15

1. String values

Path path1 = Path.of(“pandas/cuddly.png”);

Path path2 = Path.of(“c:\zooinfo\November\employees.txt”);

Path path3 = Path.of(“/home/zoodirectory

Or

2. Varargs

Path path1 = Path.of(“pandas”, “cuddly.png”);

Path path2 = Path.of(“c:”, “zooinfo”, “November”, “employees.txt”);

Path path3 = Path.of(“/”, “home”, “zoodirectory”);

Question 16

Describe Paths.get()

Answer 16

-static method defined in java.nio.file.Paths factory class

-Paths factory method
public static Path get​(String first, String… more)

-Paths creates instances of Path interface

Question 17

What type of parameters does Paths.get() take?

Answer 17

-a String value

Path path1 = Paths.get(“pandas/cuddly.png”);

Path path2 = Paths.get(“c:\zooinfo\November\employees.txt”);

Or

-varargs

Path path3 = Paths.get(“/”, “home”, “zoodirectory”);

Question 18

Describe URI

Answer 18

-a constructor from java.net.URI class

• a uniform resource identifier (URI) starts with schema words:
  file: // for local file systems,
  http: //, https://, ftp:// for remote file systems.

-URI Constructor
public URI(String str) throws URISyntaxException

Question 19

How do you convert URI to Path and Vice versa?

Answer 19

-URI to Path, using Path factory method
public static Path of(URI uri)

-URI to Path, using Paths factory method
public static Path get(URI uri)

-Path to URI, using Path instance method
public URI toURI()

URI a = new URI("file://icecream.txt");
Path b = Path.of(a);
Path c = Paths.get(a);
URI d = b.toUri();

Question 20

What are the other URI types (other than file://…)

Answer 20

http://

Path path5 = Paths.get(new URI(“http://www.wiley.com”));

ftp://

Path path6 = Paths.get(new URI(“ftp://username:secret@ftp.example.com”));

N.B. Knowing these syntaxes not expected for the exam; just know they exist.

Question 21

Describe FileSystems/FileSystem classes

Answer 21

-FileSystems creates instances of the abstract FileSystem

-FileSystems factory method
public static FileSystem getDefault()

Question 22

Describe getPath​(String first, String… more)

Answer 22

-FileSystem instance method

public Path getPath​(String first, String… more)

Question 23

Illustrate how to obtain Path instance using FileSystem

Answer 23

Path path1 = FileSystems.getDefault().getPath(“pandas/cuddly.png”);
Path path2 = FileSystems.getDefault()
.getPath(“c:\zooinfo\November\employees.txt”);
Path path3 = FileSystems.getDefault().getPath(“/home/zoodirectory”);

Question 24

How do you get remote file with FileSystems?

Answer 24

-FileSystems factory method
public static FileSystem getFileSystem​(URI uri)

-example

FileSystem fs = FileSystems.getFileSystem(
      new URI("http://www.selikoff.net")
       );
Path path = fs.getPath("duck.txt");

Question 25

Using a diagram, show relationships within NIO.2

Answer 25

Photo herefile:///var/folders/52/w8f7mgjn6ys319x4f_s5mpwh0000gn/T/com.apple.Safari/WebKitDropDestination-l4d49GeV/IMG_3144.jpeg

Question 26

How do you convert Path to java.io.File and vice versa?

Answer 26

-Path to File, using Path instance method
public default File toFile()

-File to Path, using java.io.File instance method
public Path toPath()

-examples:

File file = new File("husky.png");
Path path = file.toPath();
File backToFile = path.toFile();

Question 27

Describe the 2 file system symbols

Answer 27

. current directory

.. parent of current directory