I/O in java Part 1

File IO in Java

Prof. AshishSingh Bhatia, ast.bhatia@gmail.com,
ashish@asbspace.in, Web: asbspace.in, M:9879009551

September 18, 2012

Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, 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 IO

Understanding Streams

Input Stream

Output Stream


Streams

Sequence of bytes.
Input Stream : Data is received by some device to program.
Output Stream : Data is sent by the program to device.
Stream provides a sort of abstraction.
Recall System.out and System.in
System.in object of InputStream and System.out and
System.err is object of PrintStream class.


Streams

Sequence of bytes.


Files

File class is provided by java.io package.
An abstract reprsentation of file and directory pathnames.
Note File object is not for reading / writing files.
Used for obtaining information associated with file like
permission, time and date, path.
Directory too is treated as file and have additional method
list() to list the filename in directory.
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
boolean canRead()
boolean canWrite()
boolean cancreateNewFile()
boolean delete()
boolean exists()
String getAbsolutePath()
String getName()
String getParent()
String getPath()
boolean isAbsolute()
boolean isDirectory()
boolean isFile()
boolean isHidden()
long lastModified()
long length()

File class methods -Cont

String[] list()
File[] listFiles()
boolean mkdir()
boolean renameTo(File d)
boolean setLastModifiedDate()
boolean setReadOnly()
String toString()
String getFreeSpace()
String getTotalSpace()
String getUsableSpace()



Creating a directory.



Traversing a Directory.



Traversing a Directory.
Using FilenameFilter Interface.


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");

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

Byte Stream / Binary Stream
Only Binary data / bytes.
Read and Write [8 bytes].
Character Stream
Character Data.
Unicode Character.


Types of Streams

Only Binary data / bytes.
Read and Write [8 bytes].
Character Stream
Character Data.
Unicode Character.


Stream Base IO

Four Abstract Classes.
InputStream.
OutputStream.
Character Stream
Reader.
Writer.


Overview of IO Classes


OutputStream of IO


InputStream of IO


Writer of IO


Reader of IO


I/O in java Part 1

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I/O in java Part 1