1. IO Package in Java

2. File class Class File provides information about The class provides
Files and directories
The class provides
A constructor with a String argument
Specifying the name of a file or directory
The name can be either an absolute path or a relative path

3. Methods of the File class

4. Methods of the File class (cont’d)

5. FileFilter interface FileFilter
Used for filtering the set of files shown to the user
Method
boolean accept(File pathName)
Tests whether or not the file is acceptable
Used in conjunction with
File[] listFiles method of the File class
To list files satisfying a given filter

6. NIO Package in Java

7. Core components
NIO has two pillars
Channels
Buffers

8. Channels Channel is similar to a stream but
Is bidirectional unlike a stream
And always read from and write to a buffer
Some channel implementations in Java NIO include
FileChannel
DatagramChannel
SocketChannel
ServerSocketChannel

9. Buffers Buffer is A Buffer is typically used as Types of buffers:
A container that can hold a finite number of elements
A Buffer is typically used as
Write data to the buffer
Call the flip method
Read data out of the buffer
Either call the clear method or the compact method
Types of buffers:
ByteBuffer, CharBuffer, DoubleBuffer
FloatBuffer, IntBuffer, LongBuffer

10. Properties of Buffers Buffers have 3 main properties clear method
Capacity
Position
Limit
clear method
position=0
limit =
capacity
compact method
limit=capacity
position=
position of last unread data + 1

11. NIO package File information can also be retrieved using
Classes of the sub-packages of the java.nio package
In particular, the following classes can be used:
Path
Objects represent the location of a file or directory
Paths
provides static methods used to create a Path object
Files
provides static methods for common file and directory manipulations
DirectoryStream
enables a program to list the content of a directory

12. Path class
Path is
a programmatic representation of a path in file system
used to examine, locate, and manipulate files
composed of methods that can among other things
obtain information about path through getFileName()
compare two paths using the equals() method
instantiated by means of the get method of the Paths class
Example: Path p = Paths.get(“sample.txt”);

13. Files class
Files
provides support for common file and directory manipulations
exists(Path)
Verifies existence of a file or a directory
isReadable(Path), isWritable(Path), isExecutable(Path)
Checks file accessibility
isSameFile(Path, Path)
Checks whether two paths locate the same file
delete(Path) and deleteIfExists(Path)
Delete files or directories
copy(Path, Path)and move(Path, Path)
Copy and move files or directories

14. Files class (cont’d) Files allows for management of meta-data
size(Path)
size of specified file in bytes
isDirectory(Path)
returns true if specified path is a directory
getLastModifiedTime(Path)
File’s last modified time
getOwner(Path)
Owner of specified file
readAttributes(Path, Class)
Reads attributes of a file in one bulk operation

15. Basic File Attributes (Example)
Path file = ...;
BasicFileAttributes attr = Files.readAttributes(file, BasicFileAttributes.class);
System.out.println("creationTime: " + attr.creationTime());
System.out.println("lastAccessTime: " + attr.lastAccessTime());
System.out.println("lastModifiedTime: " + attr.lastModifiedTime());
System.out.println("isDirectory: " + attr.isDirectory());
System.out.println("size: " + attr.size());

16. Reading, writing and creating files using Files class
Buffered I/O methods for text files in Files class
newBufferedReader(Path, Charset)
opens a file for reading returning a BufferedReader
Example:
Charset charset = Charset.forName(“US-ASCII”);
BufferedReader reader = Files.newBufferedReader(file, charset);
newBufferedWriter(Path, Charset)
returns a BufferedWriter
BufferedWriter writer = Files.newBufferedWriter(file, charset);

17. Reading, writing and creating files using Files class (cont’d)
Unbuffered I/O methods for text files in Files class
newInputStream(Path, OpenOption...)
returns an InputStream for reading bytes from file
Example:
InputStream in = Files.newInputStream(file);
newOutputStream(Path, Charset)
returns a OutputStream
OutputStream out = Files.newOutputStream(file);