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Input/Output System-II

Java Programming

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Input/Output in Java The Character Stream Hierarchy Data StreamsDataInputStream,

DataOutputStreamRandomAccessFileObject Streams and Serialization The Scanner ClassesStreamTokenizer, StringTokenizer

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The Character Stream Hierarchy

ObjectReader WriterInputStreamReaderBufferedReaderCharArrayReaderFilterReaderPipedReaderStringReader

OutputStreamWriterFileWriter

BufferedWriterCharArrayWriter

FilterWriterPrintWriter

PipedWriterStringWriter

FileReader

LineNumberReader

PushbackReader

Character Streams provide direct I/O support for Unicodes.

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Writing on the consol PrintWriter is essentially a

character-oriented version of PrintStream

PrintWriter( OutputStrem os, boolean flushonNewln)

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Writing on the console PrintWriter Provides

formatted output methods -print() and println() - for all types including Object print(int intValue) print(float floatValue) print(Object objectValue)

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Demo: PrintWriterThis program prints different

data type values on the console

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Reading Text FilesReader and Writer - abstract

classesSub-classes:

InputStreamReader and OutputStreamWriter - used to work with any text represented by ASCII character set or Unicode

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Reading Text Files FileReader - subclass of

InputStreamReader, reads a byte stream and converts the bytes into integer values that represent Unicode characters

read() method returns an integer

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Demo: Reading Text FilesDemo1: Reads one character

at a time

Demo2: Uses BufferedReaderand reads one line at a time

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Writing Text FilesFileWriter, a subclass of

OutputStreamWriterConvert Unicode-char-codes

to bytes

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Writing Text Files FileWriter w =new FileWriter(destination.txt);for( int j=65; j

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Writing Text Files BufferedWriter class can be

used to write a buffered character stream

To write a preferred EOL (End Of Line) character of the host platform, use newLine()method

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Character Stream Classes

CharArrayReader & CharArrayWriter classes -implementation of input/output streams Uses a character array as the

source or destination

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Java IO Interfaces DataInput DataOutput FilenameFilter FileFilter ObjectInput ObjectOutput ObjectInputValidation ObjectStreamConstants Serializable Externalizable

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Data StreamsWhen we need to work with

data that is not represented as bytes or characters, we can use data input and data output streams.

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Data StreamsThese streams filter an

existing byte stream so that each of primitive types, boolean, byte, double, float, int, long, and short, can be read or written directly from the stream

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Data Streams ... The data input/output streams

constructors:DataInputStream(InputStream is)DataOutputStream(OutputStream os)

The argument is an existing stream that is a file or buffered stream

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Data Streams ...DataInputStream implements

DataInput interfaceDataOutputStream implement

DataOutput interface These are two of the most

useful filters in java.iopackage

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Data Streams Methods Input methods: readBoolean(),

readByte( ), readDouble(),readFloat(), readInt(),readLong(), readShort() Input Methods throw both

IOException and EOFException

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Data Streams MethodsOutput Methods:

writeBoolean() , writeByte(),writeDouble(), writeFloat(),writeInt(), writeLong() ,writeShort()Output methods throw only

the IOException

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Demo of RWDataStream.javaThis programFinds prime numbersWrite them to a file

command line arg - using writeInt(int value) methodReads the number from the

file using readInt() method

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RandomAccessFile ClassEncapsulates a random-

access fileUsed to perform I/O directly at

any specific location in the file Implements DataInput &

DataOutput interfacesDefine basic I/O methods:

getFilePointer(), length() and seek()

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RandomAccessFile Class RandomAccessFile(File fileObj, String

access) throws IOExceptionRandomAccessFile(String filename,

String access) throws IOException

fileObj File object fileName name of the fileaccess r or rw

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Demo: RandomAccessFileThe programCreates a random access fileWrites some data to it Reads it and displays it on

the console

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Object StreamsThe Object Streams are used

to read and write complete objects from and to a streamObjectInputStream and

ObjectOutputStream classes are used to perform object serialization

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Object Streams The classes which implement

the interface Serializable can be serialized serialver tool is used to find

out that a class is serializableor not

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Object Streams There are two methods which

help in performing object I/O

public abstract Object readObject() throws ClassNotFoundException,IOExcepion

public abstract void writeObject(Object obj) throws IOExcepion

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Demo: SerializableThe demo programCreates an object of Book

class which is serializableWrites the Book object to a fileReads the Book object from

the file and assigns to a Book class variable and displays its values

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The Scanner Classes StreamTokenizer filter breaks

up a stream of characters into a stream of tokens If the stream of characters is

a sentence, the tokens represent the words and punctuation marks that make up the sentence

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The Scanner Classes A non-IO class that can also

provide a scanner is StringTokenizer which implements the Enumeration interface. The individual tokens contained in a string can be enumerated using StringTokenizer

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SummaryThe Java I/O SystemRandomAccessFile ClassesThe Byte and Character

Stream HierarchiesThe Data StreamsThe Object StreamsThe Scanner Classes -

StreamTokenizer, StringTokenizer