Buffered Stream class with its methods and examples

What & Why Buffered Stream class:

Most of the examples we taken so far use unbuffered I/O.
What is unbuffered I/O?

This means each read or write request is handled directly by the underlying OS.
This can make a program much less efficient since each such request often triggers disk access, network activity, or some other operation that is relatively expensive.

Why buffered I/O?

To reduce this kind of overhead, the Java platform implements buffered I/O streams.
Buffered input streams read data from a memory area known as a buffer;

The native input API is called only when the buffer is empty.

Similarly, buffered output streams write data to a buffer;

The native output API is called only when the buffer is full.

A JAVA program can convert an unbuffered stream into a buffered stream using the buffer input and output classes.
Example:

The unbuffered stream object is passed to the constructor for a buffered stream class.

inputStream = new BufferedReader(new FileReader("Sarthak.txt"));
outputStream = new BufferedWriter(new FileWriter("CDPatel.txt"));

There are four buffered stream classes used to wrap unbuffered streams:

BufferedInputStream and BufferedOutputStream create buffered byte streams.
BufferedReader and BufferedWriter create buffered character streams.

What is Flushing in Buffered Streams?

It often makes sense to write out a buffer at critical points, without waiting for it to fill is known as flushing the buffer.
Some buffered output classes support autoflush.
AutoFlush

When autoflush is enabled, certain key events cause the buffer to be flushed.
For example, an autoflush PrintWriter object flushes the buffer on every invocation of println or format.

Manual Flush

To flush a stream manually, invoke its flush method.
The flush method is valid on any output stream but has no effect unless the stream is buffered.

BufferedInputStream class:

Syntax:

java.lang.Object
java.io.InputStream
java.io.FilterInputStream
java.io.BufferedInputStream

A BufferedInputStream adds functionality to unbuffered class to buffered class.
When the BufferedInputStream is created, an internal buffer array is created.
As bytes from the stream are read or skipped, the internal buffer is refilled as necessary from the contained input stream, many bytes at a time.
The mark operation remembers a point in the input stream.
It has five fields, two constructors and seven methods.
Field:

1. buf

Syntax: protected volatile byte[] buf
Use: The internal buffer array where the data is stored.

2. count

Syntax: protected int count
Use: The index one greater than the index of the last valid byte in the buffer.

3. marklimit

Syntax: protected int marklimit
Use: The maximum read ahead allowed after a call to the mark method before subsequent calls to the reset method fail.

4. markpos

Syntax: protected int markpos
Use: The value of the pos field at the time the last mark method was called.

5. pos

Syntax: protected int pos
Use: The current position in the buffer. This is the index of the next character to be read from the buf array.

Constructor:

Syntax:

public BufferedInputStream(InputStream in)
public BufferedInputStream(InputStream in, int size)

Use:

Creates a BufferedInputStream and saves its argument, the input stream in, for later use. An internal buffer array is created and stored in buf.

Parameters:

in - the underlying input stream.
size - the buffer size.

Throws:

IllegalArgumentException - if size <= 0.

Methods:

1. available

Syntax: public int available() throws IOException
Override: available in class FilterInputStream extends InputStream

2. close:

Syntax: public void close() throws IOException
Override: available in class FilterInputStream extends InputStream

3. mark:

Syntax: public void mark(int readlimit)
Override: available in class FilterInputStream extends InputStream

4. markSupported

Syntax: public boolean markSupported()
Override: available in class FilterInputStream extends InputStream

5. read

Syntax:

public int read() throws IOException
public int read(byte[] b, int off, int len) throws IOException

Override: available in class FilterInputStream extends InputStream

6. reset

Syntax : public void reset() throws IOException
Override: available in class FilterInputStream extends InputStream

7. skip

Syntax: public long skip(long n) throws IOException
Override: available in class FilterInputStream extends InputStream

BufferedOutputStream class:

Syntax:

java.lang.Object
java.io.OutputStream
java.io.FilterOutputStream
java.io.BufferedOutputStream

The class implements a buffered output stream.
By setting up such an output stream, an application can write bytes to the underlying output stream without necessarily causing a call to the underlying system for each byte written.
It has two fields, two constructors and two methods.
Field:

1. buf

Syntax: protected byte[] buf
Use: The internal buffer where data is stored.

2. count

Syntax: protected int count
Use: The number of valid bytes in the buffer. This value is always in the range 0 through buf.length; elements buf[0] through buf[count-1] contain valid byte data.

Constructor:

Syntax:

public BufferedOutputStream(OutputStream out)
public BufferedOutputStream(OutputStream out, int size)

Use:

Creates a new buffered output stream to write data to the specified underlying output stream.

Parameters:

out - the underlying output stream.
size - the buffer size.

Throws:

IllegalArgumentException - if size <= 0.

Methods:

1. flush

Syntax: public void flush() throws IOException
Overrides: flush in class FilterOutputStream extend OutputStream

2. write

Syntax:

public void write(byte[] b, int off, int len) throws IOException
public void write(int b) throws IOException

Overrides: write in class FilterOutputStream extend OutputStream

BufferedReader class:

Syntax:

java.lang.Object
java.io.Reader
java.io.BufferedReader

Reads text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines.
The buffer size may be specified, or the default size may be used.
The default is large enough for most purposes.
For example: BufferedReader in = new BufferedReader(new FileReader("Sarthak.txt"));
It has one field, two constructors and eight methods.
Field: lock field is inherited from class java.io.Reader
Constructors: BufferedReader

Syntax:

public BufferedReader(Reader in)
public BufferedReader(Reader in, int sz)

Use:

Creates a buffering character-input stream that uses a default-sized input buffer.

Parameters:

in - A Reader
sz - Input-buffer size

Throws:

IllegalArgumentException - If sz <= 0

Methods:

1. close:

Syntax: public void close() throws IOException
Use: Closes the stream and releases any system resources associated with it.
Throws:

IOException - If an I/O error occurs

2. lines:

Syntax: public Stream lines()
Use: Returns a Stream, the elements of which are lines read from this BufferedReader.
Returns: a Stream providing the lines of text described by this BufferedReader

3. mark:

Syntax: public void mark(int readAheadLimit) throws IOException
Overrides: mark in class Reader

4. markSupported:

Syntax: public boolean markSupported()
Overrides: markSupported in class Reader

5. read:

Syntax:

public int read() throws IOException
public int read(char[] cbuf, int off, int len) throws IOException

Overrides: read in class Reader

6. readLine:

Syntax: public String readLine() throws IOException
Use:

Reads a line of text.
A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.

Returns:

A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached

Throws: IOException - If an I/O error occurs

7. ready:

Syntax: public boolean ready() throws IOException
Overrides: ready in class Reader

8. reset:

Syntax: public void reset() throws IOException
Overrides: reset in class Reader

9. skip:

Syntax: public long skip(long n) throws IOException
Overrides: skip in class Reader

BufferedWriter class:

Syntax:

java.lang.Object
java.io.Writer
java.io.BufferedWriter

Writes text to a character-output stream, buffering characters so as to provide for the efficient writing of single characters, arrays, and strings.
The default is large enough for most purposes.
The buffer size may be specified, or the default size may be accepted.
For example: PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("ampics.txt")));
It has one field, two constructors and four methods.
Field: lock field is inherited from class java.io.Writer
Constructors:

Syntax:

public BufferedWriter(Writer out)
public BufferedWriter(Writer out, int sz)

Use:

Creates a buffered character-output stream that uses a default-sized output buffer.

Parameters:

out - A Writer
sz - Output-buffer size, a positive integer

Throws:

IllegalArgumentException - If sz <= 0

Methods:

1. close:

Syntax: public void close() throws IOException
Use: Closes the stream, flushing it first.
Throws: IOException - If an I/O error occurs

2. flush

Syntax: public void flush() throws IOException
Use: Flushes the stream.
Throws: IOException - If an I/O error occurs

3. newLine:

Syntax: public void newLine() throws IOException
Use:

Writes a line separator.
The line separator string is defined by the system property line.separator, and is not necessarily a single newline ('\n') character.

Throws: IOException - If an I/O error occurs

4. write:

Syntax:

public void write(int c) throws IOException
public void write(char[] cbuf, int off, int len) throws IOException
public void write(String s, int off, int len) throws IOException

Use:

Writes a single character.
Writes a portion of an array of characters.
Writes a portion of a String.

Overrides:

write in class Writer

Buffered Stream class with its methods and examples

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