IOStreams by Kamalakar Dandu

8/2/2019 IOStreams by Kamalakar Dandu

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Streams: An Intro

Programs need to send/receiveinformation from a variety of sources file on a disk,

data on a network,

data in memory,

data in another program.

Types of data: values, characters, image files

sound files

If the application wants to receive/senddata, it creates a stream, and reads/write to

the stream


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InputStreams Hierarchy

InputStream

FileInputStream

ByteArrayInputStream

FilterInputStream

SequenceInputStream PipedInputStream

AbstractClass extendsPublic class

ObjectInputStream

All these streams handle bytes


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Streams: An Intro...

Create Streams Add data java streams to stream

read char(byte) from stream

s

read char(byte) from stream

InputStreams are those streams that have a readingend

and the writing endis connected to a source which

supplies data (e.g. a HARD DISK).

Writing endreading end

j v a s t rj e a m

a v a s t r e a m sa

s t r e a m sa sourceva


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InputStream Class

InputStream

abstract int read()

int read(byte b[])

int read(byte b[], int off, int len)long skip(long n)

int available()

void close()

void mark(int readlimit)void reset()

boolean markSupported()

class Name

public

methods


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FileInputStream Class

FileInputStream extends InputStream

FileInputStream(File)

FileInputStream(FileDescriptor)

FileInputStream(String)native int read()

native long skip(long n)

native int available()

native void close()int read(byte b[])

int read(byte b[], int off, int len)

class Name

public

methods


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InputStream

int read()

int read(byte b[], int off, int len )

void mark(int)

long skip(long n)

int available()

void close()

int read(byte b[])

void reset()

FileInputStream

int read()int read(byte b[], int off, int len )

long skip(long n)

int available() void close()

int read(byte b[])

ex

tends

abstract methods Native Methods


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fis = new FileInputStream();

Using FileInputStream...

HD

system dependent

resources

Writing end reading end

fisis the handle to the stream. Onecan only read from this streamfis.read()will only read fromthe file in the hard disk(HD)


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Reading through

Streams Reading

open a stream (FileStream)

while more information { readinformation }

close the stream


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Example

Read from file ( given as string inthe command line )

then display contents on theconsole

Eg.FileInputDemo.java
http://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.java


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OutputStreams Hierarchy

OutputStream

FileOutputStream

ByteArrayOutputStream

FilterOutPutStream

PipedOutputStream


ObjectOutputStream
http://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.java


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OutputStream Class

OutputStream

abstract void write(int);

void write(byte[]);

void write(byte[], int, int);void flush();

void close();

class Name

public

methods
http://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.java


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FileOutputStream Class

FileOutputStream extends OutputStream

FileOutputStream(String);

FileOutputStream(String,boolean);

FileOutputStream(File);FileOutputStream(FileDescriptor);

native void write(int);

native void close();

void write(byte[]);void write(byte[], int, int);

FileDescriptor getFD();

class Name

public

methods
http://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.java


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fos = new FileOutputStream();

FileOutputStream...

HD

system dependent

resources

reading endwriting end

fis.write()will only write to thefile in the hard disk(HD)
http://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.java


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WritingthroughStreams

Writing

Open a stream (FileStream)

while more information { write information }Close the stream
http://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.java


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Example

Read form the console and

Write it to a file (given as string in the command line).

Eg: FileOutputDemo.java
http://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileInputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.java


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Class File

Uses of File class :

To extract information about filesand directories of the local filesystem

construct an object and use its

methods to obtain informationabout the files/dirs on the local filesystem
http://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.java


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Classjava.io.File

File

File (String thePath)

File (String , String fname)

File (File dir, String fname)

String getAbsolutePath()

String getCanonicalPath()

boolean exists()/ canRead()/canWrite()

long length()/lastModified();boolean isFile()/isDirectory()

boolean delete()/ renameTo(File)

class Name

public

methods
http://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.java


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Exercise

Write an application in java to displaylist of the directories or file contents of

the specified path Textfield should be present at the top, in

which we can

specify the file path. Once the file/dir in the textfield is

specified. It should display info about

the same in a textArea which is present

Eg FileTest.java
http://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileOutputDemo.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.java


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ByteArrayOutputStreams

application

Internal storage

ByteArrayOutputStream

baos.write(int)boas

ByteArrayOutputStream baos=new

ByteArrayOutputStream();

// retrieve data from stream

byte b[] = baos.toByteArray();

b

23 93143 54 155 length=5
http://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.java


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application

Internal storage


S.o.p(baos.read())

bais

ByteArrayInputStream bais=new

ByteArrayInputStream(byte[]);

23 93143 54 155

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S.o.p(baos.read())
http://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.java


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protected

InputStream in public int read()

throws IOException {

return in.read();}Implements all methods

by calling the methods

of the stream using

handle in

InputStream

FilterInputStream

BufferedInputStreamDataInputStream

LineNumberInputStreamPushbackInputStream

buffers input

give line nums for

chars:deprecated

allow bytes to be

sent back to

interface

DataInput

write primitivejava data types
http://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.java


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InputStreams

Streams available and their

functionalityapplication application

Hard Disk Array of bytes

ByteArrayInputStreamFileInputStream
http://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.java


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fis

application

Hard Disk

FileInputStream

BufferedInputStream

FileInputStream fis=new FileInputStream

(test.dat);

BufferedInputStream bis=new

BufferedInputStream (fis);

bis.read()

bisRequire another input stream asa parameter

BufferedInputStream

E.gBufferedTextInputTest.java
http://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/FileTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.java


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BufferedInputStreamClass

BufferedInputStream extends FilterStreamBufferedInputStream(InputStream)

BufferedInputStream(InputStream,int)

int available()

long skip(long n)

void close()

void mark(int)

void reset()int read(byte b[])

int read(byte b[], int off, int len)

class Namepublic

methods

Allows the use ofmark, reset and

other methods onthe inputstream
http://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.java


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Example

Read one fourth from file ( givenas string in the command line ),and then display contents on the

console. Reset it and thendisplay the first one fourth of thecontents again on the console.Eg: TestBufferedStream.java
http://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/BufferedTextInputTest.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.java


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DataInputStream

int readInt()

int read(byte b[], int

off, int len )

boolean readBoolean()

float readFloat()

long readLong()

int read(byte b[])

char readChar()

byte readByte()

String readLine()

short readShort()

int readUnsignedByte() int readUnsignedShort()

DataInput

String readUTF()

double readDouble()
http://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.java


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DataInput/OutputStreams

Read and write primitive datatypes in bit streams (actually

stored as bytes)

read and write in a machine

independent way Data must be written and read in

the same order
http://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.java


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DataOutputStream dos=new DataOutputStream (fos);

HD

FileOutputStream fos=new FileOutputStream (testdata.dat);

dos.writeboolean(true); dos.close(); fos.close();

DataInputStream dis=new DataInputStream (fis);FileInputStream fis=new FileInputStream (testdata.dat);

System.out.println(dis.readBoolean());

Information stored internally as bit/byteInternal information not available to

programmer

DataInput/OutputStreams
http://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.java


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Example

Write a program to write the following information to a file

named testItem.dat (items separated by tabs)

25.99 12 Tennis racket

345.32 6 T-shirtsWrite a second program to read and display the above

information from the file testItem.dat
http://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.java


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PrintStream

Deprecated

use PrintWriter instead
http://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.java


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Class System

An uninstantiable System class thatprovides a lot of important methods(all static) and references for otherobjects InputStream in

OutputStream out

OutputStream err

exit() gc()

arrayCopy

getProperties
http://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.java


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Reading from Keyboard

A handle to the Keyboard data isgiven to the user as a InputStream(System.in)

Programmer needs to encapsulate itwith higher level streams to obtainand process inputs

Use reader to trap characters, andthen process them depending as towhat the application requires
http://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.java


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application

String str = br.readLine()

br BufferedReader br=new BufferReader(new InputStreamReader(System.in) );

//process to obtain an integer

int i = Integer.parseInt(str);

Operating System Control returns after user

presses enter keyEg: KeyInput.java
http://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/TestBufferedStream.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.java


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Redirecting Output to File

Use setOut(OutputStream ) ofclass Systemto set the output

stream of the app

consequent commands to print()and println() are set to thatstream that was passed tosetOut
http://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.java


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applicationout

//write to System.out

System.out.println(java class);

Operating System

Normal Application
http://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.java


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Example

If the user gives a filename at thecommand prompt, then the

application will redirect output tothat file, and also to the console

if the user does not give a

filename, the application willwrite only to the console insteadof directing data to the file

Eg: RedirectOutput.java
http://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/KeyInput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.java


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Streams Heirarchy

Reader

BufferedReader

InputStreamReader

StringReader

CharArrayReaderPipedReader


FilterReader

All these streams handle chars

FileReader PushbackReader
http://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.java


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Streams Heirarchy

Writer

BufferedWriter

OuputStreamWriter

StringWriter

CharArrayWriterPipedWriter


FilterWriter

FileReader PrintWriter
http://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.java


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RandomAccessFile

Implements DataOut and DataInputIt Supports both Reading and writing to a file

Constructors:

RandomAccessFile(File file, String mode)

RandomAccessFile(String name, String mode)

The mode argument must either be equal to "r"

or "rw", indicating that the file is to be openedfor input only or for both input and output,

respectively.
http://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://iostreams/RedirectOutput.javahttp://../java/io/RandomAccessFile.htmlhttp://../java/io/File.htmlhttp://../java/lang/String.htmlhttp://../java/io/RandomAccessFile.htmlhttp://../java/lang/String.htmlhttp://../java/lang/String.htmlhttp://../java/lang/String.htmlhttp://../java/lang/String.htmlhttp://../java/io/RandomAccessFile.htmlhttp://../java/lang/String.htmlhttp://../java/io/File.htmlhttp://../java/io/RandomAccessFile.html


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Example

E.g TextIOTest.java ( Writer andRandomAccessFile )

E.g ReadStream.java ( Readers & Writersusing Applets )

Eg ReadStream.javaEg:TestIOTest.java
http://iostreams/ReadStream.javahttp://iostreams/ReadStream.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/ReadStream.java


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Object Serialization Converting the state of an object

into a serial information (binary /bytes).

Uses

Information can be sent over thenetwork to be reconstructed at theother end (rmi)

stored in a hard disk as a file, andthe object state can bereconstructed much after theobject has been removed from

memory (i.e persistence)
http://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.java


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Serializing Java

Objects Object serialization is achieved

through ObjectInputStream and

ObjectOutputStream

ObjectOutputStream is used to

write to a stream

ObjectInputStream is used to readfrom stream

class Name
http://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.java


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class Name

public

methods

ObjectOutputStreamObjectOutputStream(OutputStream)

final void writeObject(Object)

write(byte[]); write(byte[], int, int)

writeBoolean(boolean)writeByte(int); writeBytes(String)

writeChar(int); writeChars(String)

writeFloat(float); writeDouble(double)

writeFields()

write(int); writeInt(int)

writeShort(int); writeLong(long)

writeUTF(String);

defaultWriteObject();

flush(); close()

If you want to store theobject stateto a file, pass aFileInputStream handlehere

class ObjectOutputStream
http://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.java


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Serializing Java Objects

Steps to serialize object data to a stream

create an ObjectOutputStream

create object to be serialized (e.g.. Stringobject)

use the writeObject method with the objectreference as a parameter

ObjectOutputStream oos = new OOS();

String st = new String(java serialization);

oos.writeObject(st);

If you want to store theobject stateto a file, pass a

FileInputStream handlehere
http://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.java


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Steps to deserialize object state fromstream (reading from the stream)

create an ObjectInputStream

define type of handle for object

use the readObject method which returns thethe object reference to the serialized object as

an java Object reference typecast it back to the correct object type

sequence of reading is same as that of writing

Serializing Java Objects

Methods for input stream matchmethods in outputstream

OutputStream InputStreamwriteChar(char) char readChar()

ObjectInputStream ois = new OIS();String st;st = (String)ois.readObject();
http://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.java


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Example

Write a program to store a string followed by a

vector that stores james bond, 007, last line

into a file objdata.txt (this example shows

serializing the String object and the Vector object)Write a second program to read the file objdata.txt,

and display the contents on the console

Eg: OOSPoint. java
http://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/TextIOTest.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.java


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Serializing Custom Classes

An object (written by the programmer)becomes serializable by implementingthe Serializableinterface (java.io

package, and it contains no methods) Serialization is then taken care of by the

defaultWriteObject(...) method of the

ObjectOutputStream class Deserialization is similarly taken care of

by the defaultReadObject(...) of the

ObjectInputStream class
http://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.javahttp://iostreams/oosPoint.java


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S i li i C Cl
http://iostreams/SerialPoint.java


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If you want to add additional informationto the stream (to stream / file), then onehas to override the writeObject() method

in their class with signature private void

writeObject(ObjectOutputStream) throws

IOException; you will need to call the defaultWriteObject

to serialize the data of your class

after that you can add whatever data you

want to be serialized alongwith the class
http://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.java


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In such cases they will have toread data in the same reverse

order and override thereadObject() method in theirclass

private voidreadObject(ObjectInputStream

stream) throws IOException;
http://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.java


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Example

Write some String afterserializing the object , read theinfo stored after de-serializing ina separate variable (initially setto null)

Eg: NewPoint.java

Eg: SerialNewPoint.java

File Channel
http://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/SerialPoint.javahttp://iostreams/newPoint.javahttp://iostreams/SerialNewPoint.javahttp://iostreams/SerialNewPoint.javahttp://iostreams/newPoint.javahttp://iostreams/SerialNewPoint.java


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File ChannelA channel for reading, writing, mapping, andmanipulating a file.

This Slid concentrates on file locking mechanisms.

FileChannel.lock()Acquires an exclusive lock on this

channel's file.

FileChannel.lock(long position, long size,boolean shared)

Acquires a lock on the given region of this

channel's file.

The above methods return a FileLock Object.

Method : FileLock.release()

FileLockDemo.java
http://iostreams/SerialNewPoint.javahttp://iostreams/SerialNewPoint.javahttp://iostreams/SerialNewPoint.javahttp://iostreams/SerialNewPoint.javahttp://iostreams/SerialNewPoint.javahttp://d/j2sdk-1_4_1-doc/docs/api/java/nio/channels/FileChannel.htmlhttp://d/j2sdk-1_4_1-doc/docs/api/java/nio/channels/FileChannel.htmlhttp://d/j2sdk-1_4_1-doc/docs/api/java/nio/channels/FileChannel.htmlhttp://d/j2sdk-1_4_1-doc/docs/api/java/nio/channels/FileChannel.html


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E i ( d )


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Exercise (contd)

16. A need to persist the data has now arisen asthe client observes that the development team iseither getting the data from the console or is

having it stored as string attributes in theprograms. The client wishes that the data shouldbe persisted and reused by any other programs,as well. Hence, store the data in the Collection

into a file. Implement methods to read/write thedata to/from the given file. The access methodsshould be synchronized


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Documents

IOStreams by Kamalakar Dandu