I/O Fundamentals in JAVA 2

I/O Stream Fundamentals:-

• A stream is a flow of data from a source to a sink. Typically, our program is one end of that stream, and some other node (for example, a file) is the other end.
• Source and sinks are also called as input streams and output streams, respectively.
• We can read from an input stream, but we cannot write to it. Conversely, we can write to an output stream, but cannot read from it.
• Following table shows the fundamental stream classes,

 

Stream	Byte Streams	Character Streams
Source streams	InputStream	Reader
Sink streams	OutputStream	Writer

 

Data within Streams:-

• Java technology supports  raw bytes or Unicode characters in streams.
• Stream refers to byte streams and the terms reader and writer refer to character streams.
• More specifically, character input streams are implemented by subclasses of the Reader class and character output streams are implemented by subclasses of the Writer class.
• Byte it ms are implemented by subclasses of the InputStream class and byte output streams are implemented by subclasses of the OutputStream class.

Byte Streams:-

• The following describes the fundamental byte streams.

The InputStream Method:-

• Three methods mentioned below provide access to the data from the input stream:

int read()

int read(byte[] buff)

int read(byte[] buff, int offset, int length)

• The first method returns an integer, which contains either a byte read from the stream, or a –1, which indicates the end of a file condition.
• The other two methods read a stream into a byte array and return the number of bytes read.
• The two int arguments in the third method indicate a sub range in the target array that needs to be filled.

Note:- For efficiency, always read data in the largest practical block, or use buffered streams.

 

void close()

• When we have finished with a stream, close it. If we have a stack of streams then use filter streams to close the stream at the top the stack. This operation also closes the lower streams.

 

int available()

• This method reports a number of bytes that are immediately available to be read from the stream.
• Real read operation following this call may return more bytes.

 

long skip(long n)

• It discards the specified number of bytes from the stream.

 

 

boolean markSupported()

void mark(int readlimit)

void reset()

• We can use these methods to perform push-back operations on a stream, if supported by that stream.
• The markSupported() method does return true if the mark() and reset() methods are operational for that particular stream.
• The mark(int) method indicates that the current point in the stream should be noted and a buffer big enough for at least the specified argument number of bytes should be allocated.
• The parameter of the mark(int) method specifies the number of bytes that can be re-read by calling reset() method.
• After performing the subsequent read() operations, and calling the reset() method returns the input stream to the point you marked.
• If you read past the marked buffer, reset() has no meaning.

The OutputStream Methods:-

• The following methods write to the output stream:

void write(int)

void write(byte[] buff)

void write(byte[] buff, int off, int length)

• Try to write the data in largest practical block.

 

void close()

• We should close output streams when we have finished with them. Again if we have a stack and close the top one, this closes the rest of the streams.

 

void flush()

• Sometimes an output stream accumulates writes before committing them. The flush() method enables we to force writes.

Character Streams:-

• The following describes the fundamental character streams.

The Reader Methods:-

• Methods mentioned below provide access to the character data from the reader:

int read()

int read(char[] cbuf)

int read(char[] cbuf, int offset, int length)

• The first method returns an int, which either a Unicode character read from the stream, or a -1, which indicates the end of file condition.
• The other two methods read from a character array and return the number of bytes read.
• The two int arguments in the third method indicate a sub range in target array that needs to be filled.

 

void close()

boolean ready()

long skip(long n)

boolean markSupported()

void mark(int readAheadLimit)

void reset()

• Those methods are analogous to the input stream versions.

The Writers Methods:-

• The following methods write to the writer:

 

void write(int c)

void write(char[] cbuf)

void write(char[] cbuf, int offset, int length)

void write(String string)

void write(String string, int offset, int length)

• Similar to output streams, writers include the close and flush methods.

void close()

void flush()

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