Java I/O Part 1

File IO in Java

Prof. AshishSingh Bhatia, [email protected],[email protected], Web: asbspace.in, M:9879009551

September 18, 2012

Prof. AshishSingh Bhatia, [email protected], [email protected], Web: asbspace.in, M:9879009551 1

AGENDA

Understanding Streams

Streams

Files

File class methods

File class methods -Cont

Programs using File class

Program to rename a file.

Program to delete a file.

Types of Streams

Stream Base IO

Overview of IO Classes

OutputStream of IO

InputStream of IO

Writer of IO

Reader of IOProf. AshishSingh Bhatia, [email protected], [email protected], Web: asbspace.in, M:9879009551 2

Understanding Streams

Input Stream

Output Stream


Streams

I Sequence of bytes.

I Input Stream : Data is received by some device to program.

I Output Stream : Data is sent by the program to device.

I Stream provides a sort of abstraction.

I Recall System.out and System.in

I System.in object of InputStream and System.out andSystem.err is object of PrintStream class.


Streams








Files

I File class is provided by java.io package.

I An abstract reprsentation of file and directory pathnames.

I Note File object is not for reading / writing files.

I Used for obtaining information associated with file likepermission, time and date, path.

I Directory too is treated as file and have additional methodlist() to list the filename in directory.

I public File(String pathname)

public File(String parent, String child)

public File(File parent, String child)

public File(URI uri


Files









public File(URI uri


File class methods

I boolean canRead()

I boolean canWrite()

I boolean cancreateNewFile()

I boolean delete()

I boolean exists()

I String getAbsolutePath()

I String getName()

I String getParent()

I String getPath()

I boolean isAbsolute()

I boolean isDirectory()

I boolean isFile()

I boolean isHidden()

I long lastModified()

I long length()Prof. AshishSingh Bhatia, [email protected], [email protected], Web: asbspace.in, M:9879009551 16

File class methods -Cont

I String[] list()

I File[] listFiles()

I boolean mkdir()

I boolean renameTo(File d)

I boolean setLastModifiedDate()

I boolean setReadOnly()

I String toString()

I String getFreeSpace()

I String getTotalSpace()

I String getUsableSpace()



I Program to rename a file.

I Program to delete a file.

I Creating a directory.

I Traversing a Directory.

I Using FilenameFilter Interface.


Program to rename a file.

import java.io.*;

import java.util.Scanner;

public class Rename

{public static void main(String args[]) {File f1, f2;

Scanner s = new Scanner(System.in);

System.out.println("Enter the file name : ");

String name old = s.nextLine();

System.out.println("Enter the new name : ");

String name new = s.nextLine();

f1 = new File(name old);

f2 = new File(name new);

if(f1.renameTo(f2))

System.out.println("File renamed");

else

System.out.println("Error Occured");

}}


Program to delete a file.

import java.io.*;

import java.util.Scanner;

public class Rename

{public static void main(String args[]) {File f1;

Scanner s = new Scanner(System.in);

System.out.println("Enter the file name : ");

String name = s.nextLine();

f1 = new File(name);

if(f1.exists())

{if(f1.delete())

System.out.println("File deleted");

else

System.out.println("Error Occured");

}}}


Types of Streams

I Byte Stream / Binary StreamI Only Binary data / bytes.I Read and Write [8 bytes].

I Character StreamI Character Data.I Unicode Character.


Stream Base IO

I Four Abstract Classes.I Byte Stream / Binary Stream

I InputStream.I OutputStream.

I Character StreamI Reader.I Writer.


Overview of IO Classes


OutputStream of IO


InputStream of IO


Writer of IO


Reader of IO


Java I/O Part 1

Education

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