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1

Top IO Hierarchy

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2

Input Stream

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3

Output Stream

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4

Reader

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5

Writer

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6

Streams

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7

InputStreamReader

BufferedReader stdin = new BufferedReader (

new InputStreamReader ( System.in ) );

System.in is an object of InputStream

2003 Prentice Hall, Inc. All rights reserved.

8FileReader & FileWriter

BufferedReader in = new BufferedReader (

new FileReader ( “foo.in” ) );

PrintWriter out = new PrintWriter (

new BufferedWriter (

new FileWriter (“foo.out” ) ) );

Note: System.out and System.err are PrintWriter objects

2003 Prentice Hall, Inc. All rights reserved.

9

Reading from binary file

FileInputStream fis =

new FileInputStream(myFileObj);

ObjectInputStream ois =

new ObjectInputStream(fis);

int i = ois.readInt();

String today = (String) ois.readObject();

Date date = (Date) ois.readObject();

ois.close();

2003 Prentice Hall, Inc. All rights reserved.

10

How to tell end of file

try { read from file}catch ( EOFException endOfFileException ) { do what you need to do when

end of file is reached}

Other ways possible. This is the recommended method.

2003 Prentice Hall, Inc. All rights reserved.

11

Writing to binary file

FileOutputStream fos = new FileOutputStream(myFileObj);

ObjectOutputStream oos =

new ObjectOutputStream(fos);

oos.writeInt(12345);

oos.writeObject("Today");

oos.writeObject(new Date());

oos.close();

2003 Prentice Hall, Inc. All rights reserved.

12

Reading from text file

BufferedReader input =

new BufferedReader(

new FileReader( myFile ) );

String text = input.readLine();

input.read(myCharArray, off, len);

input.close();

2003 Prentice Hall, Inc. All rights reserved.

13

Writing to text file

BufferedWriter output =

new BufferedWriter(

new FileWriter( myFile ) );

String text = “hello \n”;

output.write(text);

output.write(myCharArray,off,len);

output.flush() ;

output.close();

2003 Prentice Hall, Inc. All rights reserved.

14

Random Access Files

– Use fixed length for every record• Easy to calculate record locations

100bytes

100bytes

100bytes

100bytes

100bytes

100bytes

0 100 200 300 400 500

byte offsets

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15

Random Access File Methods

RandomAccessFile raFile = new RandomAccessFile( fileObj, "rw" );raFile.seek( ( recordNumber - 1 ) *

RandomAccessAccountRecord.SIZE );raFile.writeInt( 12345 );raFile.writeDouble( getBalance() );raFile.writeChars( buffer.toString() );int i = raFile.readInt();double d = raFile.readDouble();char c = raFile.readChar();

raFile.close();