The document discusses file input/output (IO) in Java. It provides an overview of key IO classes like OutputStream, InputStream, Writer, and Reader. It then describes common methods of each class for writing bytes/characters to output streams and reading bytes/characters from input streams, such as write(), read(), flush(), and close(). The document also covers bridge classes like OutputStreamWriter and InputStreamReader that allow bytes and characters to be used together.

1. File IO in Java
Prof. AshishSingh Bhatia, ast.bhatia@gmail.com,
ashish@asbspace.in, Web: asbspace.in, M:9879009551
September 21, 2012
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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
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3. Overview of IO Classes
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4. OutputStream of IO
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5. InputStream of IO
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6. Writer of IO
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7. Reader of IO
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8. Methods of OutputStream Class
public void write(int b)
Writes a single byte to an output stream. Why we need int as
argument?
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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.
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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].
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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.
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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
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13. Methods of Writer Class
public void write(int ch)
Writes a single character to an output stream. Why we need
int as argument?
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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.
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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
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18. Methods of Writer Class Extra
String is a sequence of Character.
public void write(String s)
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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)
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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)
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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)
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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)
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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.
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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.
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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)
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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.
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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.
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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)
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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()
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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()
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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()
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32. Methods of Reader Class
public int read()
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33. Methods of Reader Class
public int read()
public int read(char[] b)
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34. Methods of Reader Class
public int read()
public int read(char[] b)
public int read(char[] b, int offset, int len)
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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)
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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()
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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)
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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()
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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()
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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()
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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.
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44. OutputStreamWriter
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45. InputStream Reader
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46. FileInput and FileOutput Stream
Output and input of binary files.
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47. FileInput and FileOutput Stream
Output and input of binary files.
FileOutputStream create and write bytes in to physical file.
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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.
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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.
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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()
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51. FileDescriptor
Whenever any file is opened for input or output, it uses a file
descriptor.
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52. FileDescriptor
Whenever any file is opened for input or output, it uses a file
descriptor.
0=Standard Input
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53. FileDescriptor
Whenever any file is opened for input or output, it uses a file
descriptor.
0=Standard Input
1=Standard Output
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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
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