03. File & Path APIs

Files & Path APIs

In this section, you will learn to:

• Use the Files and Path APIs
• Describe the different file open options and know when to use each

Files API

The Files API is Java's Swiss Army knife for file operations. It contains static methods for doing all sorts of file operations.

Which of the following is the Java Files API not useful for?

Reading and writing files on the local file system

Copying a local file to a mounted network drive

Giving yourself permissions to an existing file

Downloading a URL from the Internet

Telling whether a Path points to a file or a directory

SOLUTION:

Downloading a URL from the Internet

File Open Options

When you create, read, or write a file, there are standard modes that you can use to do so. Java uses the StandardOpenOptions class to encapsulate all these modes.

Here are some of the common modes:

Option	Description
READ	Open a file for reading, fail if it doesn't exist.
CREATE	Create a file.
CREATE_NEW	Same as CREATE, but fail if the file already exists.
WRITE	Open a file for writing.
APPEND	Same as WRITE, but write to the end of the file.

You are allowed to use more than one option at a time.

QUIZ QUESTION::

Match each file open option to what it does:

ANSWER CHOICES:

Open a file for writing

Open a file for reading, fail if it doesn't exist

Delete the file when it is closed

Create a file, but fail if the file already exists

Create a file

Open a file for writing, but always write at the end of the file

File Open Option	What it Does
READ
CREATE
CREATE_NEW
WRITE
APPEND
DELETE_ON_CLOSE

SOLUTION:

File Open Option	What it Does
WRITE	Open a file for writing
READ	Open a file for reading, fail if it doesn't exist
DELETE_ON_CLOSE	Delete the file when it is closed
CREATE_NEW	Create a file, but fail if the file already exists
CREATE	Create a file
APPEND	Open a file for writing, but always write at the end of the file

Path API

A Path is Java's way to refer to a file on a file system:

Path p = Path.of("your/path/here");

All paths either refer to files or directories.

• A file contains stored data or bytes.
• A directory contains zero or more files.

All paths are either absolute or relative.

• Absolute paths start with a forward-slash (/) (known as the root directory on Mac and Linux), or a drive name on Windows.
• Relative paths are only meaningful relative to some other starting point. They do not start with a forward slash or drive name.

Note that the Path object in Java always uses forward-slashes to delimit the parts of the path String, even if the underlying file system uses backslashes (such as the NTFS file system on Windows).

Path API Demo

QUIZ QUESTION::

Match the kind of path with its description

ANSWER CHOICES:

Uses a starting point, usually the current working directory where the program is running.

Starts with the root directory (/) on Linux and Mac, or a drive name on Windows.

Kind of path	Description
Absolute path
Relative path

SOLUTION:

Kind of path	Description
Relative path	Uses a starting point, usually the current working directory where the program is running.
Absolute path	Starts with the root directory (/) on Linux and Mac, or a drive name on Windows.

Which of the following are absolute paths?

/

C:/Documents/Udacity/FinalProjectRubric.xls

udacity/Downloads

../home/../home/local/bin/

/usr/lib/jvm/java-11-openjdk-amd64/bin/java

SOLUTION:

• `/`
• `C:/Documents/Udacity/FinalProjectRubric.xls`
• `/usr/lib/jvm/java-11-openjdk-amd64/bin/java`

Further Reading

• Files JavaDoc
• Path JavaDoc
• Paths JavaDoc
• StandardOpenOption JavaDoc