Programming language JAVA Input output opearations

File
• Long-term storage of large amounts of data
• Persistent data exists a5er termina6on of program
• Files stored on secondary storage devices
– Magne6c disks
– Op6cal disks
– Magne6c tapes
• Sequen6al and random access ﬁles
2

File Class
• Provides useful informa6on about a file or directory
• Does not open files or process files
• To obtain or manipulate path, 6me, date,
permissions etc
• Constructor
– File(String directoryPath)
– File(String directoryPath, String fileName)
– File(File dirObj, String fileName)
• Example: FileDemo.java
3

Directory Class
• Directories are also files
• Contains list of files and directories
• For DirectoryisDirectory() returns true
String[] list()
– returns an array of strings that gives the files and
directories contained
File[] listFiles()
– Returns array of File objects
• Example: DirectoryDemo.java
4

Stream Classes
• Java views a File as a stream of bytes.
– File ends with end-of-ﬁle marker or a speciﬁc byte number
– File as a stream of bytes associated with an object.
– Java also associates streams with devices
• System.in, System.out, and System.err
– Streams can be redirected
• Stream is an abstrac6on that either produces or
consumes informa6on
5

Stream Classes
• Java’s stream-based I/O is built upon four
abstract classes.
– InputStream, OutputStream (for byte streams)
– Reader, Writer (for character streams)
• They form separate hierarchies
• Use the character stream classes when working
with characters or strings
• Use the byte stream classes when working with
bytes or other binary objects
6

Byte Stream Classes
• Byte-Stream classes are topped by InputStream and
OutputStream classes
• InputStream is an abstract class that defines Java’s
model of streaming byte input.
int available() void close() int read()
int read(byte buff[]) int read(byte buff[], int off, int num)
• OutputStream is an abstract class that defines Java’s
model of streaming byte output.
void flush() void close() void write(int b)
void write(byte buff[]) void write(byte buff[], int off, int num)
7

FileInputStream
• FileInputStream class creates an InputStream that
you can use to read bytes from a file
• Constructors
– FileInputStream(String filePath)
– FileInputStream(File fileObj)
• Example: FileInputStreamDemo.java
8

FileOutputStream
• FileOutputStream class creates an OutputStream
that you can use to write bytes to a file
• Constructors
– FileOutputStream(String filePath)
– FileOutputStream(File fileObj)
– FileOutputStream(String path, boolean append)
– FileOutputStream(File obj, boolean append)
• Example: FileOutputStreamDemo.java, FileCopyDemo.java
9

Character Streams
• Character Stream classes are topped by Reader and
Writer class
• Reader is an abstract class that defines Java’s model
of streaming character input
void close() int read() int read(char buff[])
int read(char buff[], int off, int num)
• Writer is an abstract class that defines Java’s model
of streaming character output
void flush() void close() void write(int ch)
void write(char buff[]) void write(char buff[], int off, int num)
void write(String s) void write(String s, int off, int num) 10

FileReader
• FileReader class creates a Reader that you can use to
read the contents of a file
• Constructors
– FileReader(String filePath)
– FileReader(File fileObj)
• Example: FileReaderDemo.java
11

FileWriter
• FileWriter class creates a Writer that you can use to
write to a file
• Constructors
– FileWriter(String filePath)
– FileWriter(File fileObj)
– FileWriter(String path, boolean append)
– FileWriter(File obj, boolean append)
• Example: FileWriterDemo.java
12

BufferedReader
• BufferedReader is a Reader that buffers input
• It improves performance by reducing the number of
6mes data us actually physically read from the input
stream
• Constructors
– BufferedReader(Reader reader)
– BufferedReader(Reader reader, int buffSize)
• Example: BufferedReaderDemo.java
13

BufferedWriter
• BufferedWriter is a Writer that buffers output
• It improves performance by reducing the number of
6mes data actually physically wricen to the output
stream
• Constructors
– BufferedWriter(Writer writer)
– BufferedWriter(Writer writer, int buffSize)
• Example: BufferedWriterDemo.java
14

Serializa6on
• Serializa6on is the process of wri6ng the state of an
object to a byte stream
– This is useful when you want to save the state of your
program to a persistent storage such as ﬁle
– Later these objects can be restored by using the process of
deserializa6on
• Serializa6on can be achieved by implemen6ng
Serializable interface
15

Object(Input/Output)Stream
• ObjectInputStream class extends the InputStream
class
• It is responsible for reading objects from a stream
• ObjectOutputStream class extends the
OutputStream class
• It is responsible for wri6ng objects to a stream
• Example: ObjectSerializaJonDemo.java
16

Data(Input/Output)Stream
• DataInputStream & DataOutputStream enable to
write or read primi6ve data to or from a stream
• They implement the DataOutput & DataInput
interfaces respec6vely
• Constructors
– DataOutputStream(OutputStream os)
– DataInputStream(InputStream is)
• Example: DataIODemo.java
18

Console
• It is used to read and write to the console
• It supplies no constructor. A Console object is
obtained by calling System.console()
• Important Methods
– prinf,
– readLine
– readPassword
• Example: ConsoleDemo.java
19

Programming language JAVA Input output opearations

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