File Handling in java.

1. File IO in Java
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com,
ashish@asbspace.in, Web: asbspace.in, M:9879009551
September 21, 2012
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 1

2. AGENDA
Overview of IO Classes
OutputStream of IO
InputStream of IO
Writer of IO
Reader of IO
Methods of OutputStream Class
Methods of Writer Class
Methods of Writer Class Extra
Methods of InputStream Class
Methods of Reader Class
InputStream Usage
OutputStream Usage
Bridge Classes
OutputStreamWriter
InputStream Reader
FileInput and FileOutput Stream
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 2

3. Overview of IO Classes
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 3

4. OutputStream of IO
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 4

5. InputStream of IO
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 5

6. Writer of IO
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 6

7. Reader of IO
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 7

8. Methods of OutputStream Class
public void write(int b)
Writes a single byte to an output stream. Why we need int as
argument?
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 8

9. Methods of OutputStream Class
public void write(int b)
Writes a single byte to an output stream. Why we need int as
argument?
public void write(byte[] b)
Writes complete byte array in to an outputstream.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 9

10. Methods of OutputStream Class
public void write(int b)
Writes a single byte to an output stream. Why we need int as
argument?
public void write(byte[] b)
Writes complete byte array in to an outputstream.
public void write(byte[] b, int offset, int len)
Write a subrange from offset to specified length[number of
bytes].
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 10

11. Methods of OutputStream Class
public void write(int b)
Writes a single byte to an output stream. Why we need int as
argument?
public void write(byte[] b)
Writes complete byte array in to an outputstream.
public void write(byte[] b, int offset, int len)
Write a subrange from offset to specified length[number of
bytes].
public void flush()
Flushes the output buffer. Ensures the contents are written to
the destination.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 11

12. Methods of OutputStream Class
public void write(int b)
Writes a single byte to an output stream. Why we need int as
argument?
public void write(byte[] b)
Writes complete byte array in to an outputstream.
public void write(byte[] b, int offset, int len)
Write a subrange from offset to specified length[number of
bytes].
public void flush()
Flushes the output buffer. Ensures the contents are written to
the destination.
public void close()
Closes the outputstream. Further write will generate
IOException
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 12

13. Methods of Writer Class
public void write(int ch)
Writes a single character to an output stream. Why we need
int as argument?
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 13

14. Methods of Writer Class
public void write(int ch)
Writes a single character to an output stream. Why we need
int as argument?
public void write(char[] ch)
Writes complete character array in to an outputstream.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 14

15. Methods of Writer Class
public void write(int ch)
Writes a single character to an output stream. Why we need
int as argument?
public void write(char[] ch)
Writes complete character array in to an outputstream.
public void write(char[] b, int offset, int len)
Write a subrange from offset to specified length[number of
character].
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 15

16. Methods of Writer Class
public void write(int ch)
Writes a single character to an output stream. Why we need
int as argument?
public void write(char[] ch)
Writes complete character array in to an outputstream.
public void write(char[] b, int offset, int len)
Write a subrange from offset to specified length[number of
character].
public void flush()
Flushes the output buffer. Ensures the contents are written to
the destination.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 16

17. Methods of Writer Class
public void write(int ch)
Writes a single character to an output stream. Why we need
int as argument?
public void write(char[] ch)
Writes complete character array in to an outputstream.
public void write(char[] b, int offset, int len)
Write a subrange from offset to specified length[number of
character].
public void flush()
Flushes the output buffer. Ensures the contents are written to
the destination.
public void close()
Closes the writer. Further write will generate IOException
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 17

18. Methods of Writer Class Extra
String is a sequence of Character.
public void write(String s)
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 18

19. Methods of Writer Class Extra
String is a sequence of Character.
public void write(String s)
public void write(String s, int offset, int len)
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 19

20. Methods of Writer Class Extra
String is a sequence of Character.
public void write(String s)
public void write(String s, int offset, int len)
public void append(char ch)
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 20

21. Methods of Writer Class Extra
String is a sequence of Character.
public void write(String s)
public void write(String s, int offset, int len)
public void append(char ch)
public void append(CharSequence cs)
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 21

22. Methods of Writer Class Extra
String is a sequence of Character.
public void write(String s)
public void write(String s, int offset, int len)
public void append(char ch)
public void append(CharSequence cs)
public void append(CharSequence cs, int offset,
int len)
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 22

23. Methods of InputStream Class
public int read()
Read the integer representation of the next available byte of
input. Returns -1 when the end of file is encountered.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 23

24. Methods of InputStream Class
public int read()
Read the integer representation of the next available byte of
input. Returns -1 when the end of file is encountered.
public int read(byte[] b)
Attempt to read up to b.length bytes in the the b array.
Returns the number of actual bytes read. -1 is returned when
the end of file is encountered.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 24

25. Methods of InputStream Class
public int read()
Read the integer representation of the next available byte of
input. Returns -1 when the end of file is encountered.
public int read(byte[] b)
Attempt to read up to b.length bytes in the the b array.
Returns the number of actual bytes read. -1 is returned when
the end of file is encountered.
public int read(byte[] b, int offset, int len)
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 25

26. Methods of InputStream Class
public int read()
Read the integer representation of the next available byte of
input. Returns -1 when the end of file is encountered.
public int read(byte[] b)
Attempt to read up to b.length bytes in the the b array.
Returns the number of actual bytes read. -1 is returned when
the end of file is encountered.
public int read(byte[] b, int offset, int len)
public long skip(long count)
count indicates number of bytes to be skipped and return the
number of byte skipped or -1 in case of end of file.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 26

27. Methods of InputStream Class
public int read()
Read the integer representation of the next available byte of
input. Returns -1 when the end of file is encountered.
public int read(byte[] b)
Attempt to read up to b.length bytes in the the b array.
Returns the number of actual bytes read. -1 is returned when
the end of file is encountered.
public int read(byte[] b, int offset, int len)
public long skip(long count)
count indicates number of bytes to be skipped and return the
number of byte skipped or -1 in case of end of file.
public int available()
Number of bytes available for reading.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 27

28. Methods of InputStream Class
public int read()
Read the integer representation of the next available byte of
input. Returns -1 when the end of file is encountered.
public int read(byte[] b)
Attempt to read up to b.length bytes in the the b array.
Returns the number of actual bytes read. -1 is returned when
the end of file is encountered.
public int read(byte[] b, int offset, int len)
public long skip(long count)
count indicates number of bytes to be skipped and return the
number of byte skipped or -1 in case of end of file.
public int available()
Number of bytes available for reading.
public void mark(int readlimit)
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 28

29. Methods of InputStream Class
public int read()
Read the integer representation of the next available byte of
input. Returns -1 when the end of file is encountered.
public int read(byte[] b)
Attempt to read up to b.length bytes in the the b array.
Returns the number of actual bytes read. -1 is returned when
the end of file is encountered.
public int read(byte[] b, int offset, int len)
public long skip(long count)
count indicates number of bytes to be skipped and return the
number of byte skipped or -1 in case of end of file.
public int available()
Number of bytes available for reading.
public void mark(int readlimit)
public void reset()
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 29

30. Methods of InputStream Class
public int read()
Read the integer representation of the next available byte of
input. Returns -1 when the end of file is encountered.
public int read(byte[] b)
Attempt to read up to b.length bytes in the the b array.
Returns the number of actual bytes read. -1 is returned when
the end of file is encountered.
public int read(byte[] b, int offset, int len)
public long skip(long count)
count indicates number of bytes to be skipped and return the
number of byte skipped or -1 in case of end of file.
public int available()
Number of bytes available for reading.
public void mark(int readlimit)
public void reset()
public boolean markSupported()
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 30

31. Methods of InputStream Class
public int read()
Read the integer representation of the next available byte of
input. Returns -1 when the end of file is encountered.
public int read(byte[] b)
Attempt to read up to b.length bytes in the the b array.
Returns the number of actual bytes read. -1 is returned when
the end of file is encountered.
public int read(byte[] b, int offset, int len)
public long skip(long count)
count indicates number of bytes to be skipped and return the
number of byte skipped or -1 in case of end of file.
public int available()
Number of bytes available for reading.
public void mark(int readlimit)
public void reset()
public boolean markSupported()
public void close()
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 31

32. Methods of Reader Class
public int read()
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 32

33. Methods of Reader Class
public int read()
public int read(char[] b)
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 33

34. Methods of Reader Class
public int read()
public int read(char[] b)
public int read(char[] b, int offset, int len)
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 34

35. Methods of Reader Class
public int read()
public int read(char[] b)
public int read(char[] b, int offset, int len)
public long skip(long count)
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 35

36. Methods of Reader Class
public int read()
public int read(char[] b)
public int read(char[] b, int offset, int len)
public long skip(long count)
public boolean ready()
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 36

37. Methods of Reader Class
public int read()
public int read(char[] b)
public int read(char[] b, int offset, int len)
public long skip(long count)
public boolean ready()
public void mark(int readlimit)
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 37

38. Methods of Reader Class
public int read()
public int read(char[] b)
public int read(char[] b, int offset, int len)
public long skip(long count)
public boolean ready()
public void mark(int readlimit)
public void reset()
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 38

39. Methods of Reader Class
public int read()
public int read(char[] b)
public int read(char[] b, int offset, int len)
public long skip(long count)
public boolean ready()
public void mark(int readlimit)
public void reset()
public boolean markSupported()
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 39

40. Methods of Reader Class
public int read()
public int read(char[] b)
public int read(char[] b, int offset, int len)
public long skip(long count)
public boolean ready()
public void mark(int readlimit)
public void reset()
public boolean markSupported()
public void close()
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 40

41. InputStream Usage
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42. OutputStream Usage
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43. Bridge Classes
OutputStreamWriter and InputStreamReader
Character Base Stream Classes which inturns work on bytes.
Handles unicode character and bytes both.
Encoding and Decoding of unicode character from and to
various character set.
java.nio.charset package has classes which handle
encoding and decoding.
class Charset represents different character set.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 43

44. OutputStreamWriter
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 44

45. InputStream Reader
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 45

46. FileInput and FileOutput Stream
Output and input of binary files.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 46

47. FileInput and FileOutput Stream
Output and input of binary files.
FileOutputStream create and write bytes in to physical file.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 47

48. FileInput and FileOutput Stream
Output and input of binary files.
FileOutputStream create and write bytes in to physical file.
If file exists it overwrites it until append flag is used.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 48

49. FileInput and FileOutput Stream
Output and input of binary files.
FileOutputStream create and write bytes in to physical file.
If file exists it overwrites it until append flag is used.
Inherits all the methods from the OutputStream.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 49

50. FileInput and FileOutput Stream
Output and input of binary files.
FileOutputStream create and write bytes in to physical file.
If file exists it overwrites it until append flag is used.
Inherits all the methods from the OutputStream.
Additional methods are
public FileDescriptor getFD()
public FileChannel getChannel()
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 50

51. FileDescriptor
Whenever any file is opened for input or output, it uses a file
descriptor.
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 51

52. FileDescriptor
Whenever any file is opened for input or output, it uses a file
descriptor.
0=Standard Input
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 52

53. FileDescriptor
Whenever any file is opened for input or output, it uses a file
descriptor.
0=Standard Input
1=Standard Output
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 53

54. FileDescriptor
Whenever any file is opened for input or output, it uses a file
descriptor.
0=Standard Input
1=Standard Output
2=Standard Error
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com, ashish@asbspace.in, Web: asbspace.in, M:9879009551 54