various io stream classes .47

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Various I/O Stream Classes


Objectives

On completion of this period, you would be able to learn• Concept of streams• Various input and output stream classes


Recap

In the previous classes, you have studied about exception handling mechanism in java

• Types of exceptions in java

Concept of Stream• Java performs I/O through streams

•A stream is an abstraction that either produces or consumes information

•A stream is linked to an I/O device by Java I/O system

•All streams behave in the same manner, even if the actual physical device they are linked to differ

•Thus, same I/O classes and methods can be applied to any type of device

•For example, the same methods that are used to write console can also be used to write to a disk file

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Concept of Stream

Key Board

Mouse

Memory

Disk

Network

Screen

printer

Memory

Disk

Network

Java Program

The following figure gives the relationship of java program with I/O devices

Fig. 47.1 Relationship of Java programs with I/O devices

Concept of Stream• The Fig. 47.1 shows in Java all I/O devices may be used with stream

•For example, the same methods that are used to write console can also be used to write to a disk file

• java implements streams within class hierarchies defined in java.io. package



Concept of Streams

• Input refers to flow of data into a program • Output refers to flow of data out of a program as

shown in Fig. 47.1


Concept of Streams Contd..

• I/O operations are complex to understand• But more flexible and powerful • Developers have focused their attention for non

keyboard oriented data handling• Developers wanted to perform platform

independent I/O, hence the complexity


Various I/O Stream Classes• java.io package defines I/O in terms of streams

• Two types of Streams1. Byte streams

• 8 bits, binary data-based• Examples: InputStream and OutputStream

classes2. Character streams

• 16 bits, text-based• Examples: Reader and Writer classes

9CM604.47 10

Various I/O Stream Classes• The following diagrams show the class hierarchies of

the stream classes• InputStream• OutputStream• Reader• Writer


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Object

InputStream

FileInputStream SequenceInpuStream

PipedInpuStream ObjectInputStream

ByteArrayInputStream StringBufferInputStream

FilterInpuStream

BufferedInpuStream PushBackInputSteam

DataInputStream

DataInput

Hierarchy of InputStream classes

Fig. 47.2


Object

OutputStream

FileOutputStream ObjectOutputStream

PipedOutputStream ByteArrayOutputStream

FilterOutpuStream

BufferedOutpuStream PushBackOutputSteam

DataOutputStream

DataOutput

Hierarchy of OutputStream Classes

Fig. 47.3


Object

Reader

BufferedReader StringReader

CharArrayReader PipeReader

InputStreamReader FilterReader

FileReader PushBackReader

Hierarchy of Reader Classes

Fig. 47.4

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Object

Writer

BufferedWriter PrintWriter

CharArrayWriter StringWriter

FilterWriter PipeWriter

FileReader

OutputStreamWriter

FileWriter

Hierarchy of Writer Classes

Fig No 47.5

Simple Input and Output Streams

• FileInputStream and FileOutputStream • Used to read data from or write data to a file on the native

file system • PipedInputStream and PipedOutputStream

• Implements the input and output components of a pipe• Pipes are used to channel the output from one program (or

thread or code block) into the input of another • A PipedInputStream must be connected to a

PipedOutputStream and vice versa


Simple Input and Output Streams

• ByteArrayInputStream and ByteArrayOutputStream • Reads data from or writes data to a byte array in memory

• SequenceInputStream • Concatenates multiple input streams into one input stream

• StringBufferInputStream • Allows programs to read from a StringBuffer as if it were

an input stream


Filtered Streams • FilterInputStream and FilterOutputStream are subclasses of

InputStream and OutputStream• Both are abstract classes • These classes defines the interface for filtered streams• Filtered streams process the data as its being read or written• DataInputStream and DataOutputStream

• Reads or writes primitive Java data types in a machine independent format


Filtered Streams • BufferedInputStream and BufferedOutputStream

• This is an efficient stream that buffers data while reading or writing

• LineNumberInputStream • An input stream that keeps track of line numbers while

reading • PushbackInputStream

• An input stream with a one-byte pushback buffer PrintStream

• An output stream with convenient printing methods



Summary

• Flow of bits of information either into the program or from the program to and from

• Various input and output devices• Stream is a logical entity that either produces or

consumes information

• Two types of Streams1. Byte streams2. Character streams


Quiz

1. Which of the following is not Byte streams

A. Input StreamB. Output StreamC. ReaderD. None

2. Streams is ordered sequences of data that have a source or a destination

A. TrueB. False


Quiz


Frequently Asked Questions

1. Explain the concept of Streams2. Explain the various input output stream classes

various io stream classes .47

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