Stream vs Reader and writer
In this chapter you will learn:
- Stream vs Reader and writer
- Get to know InputStream
- Get to know OutputStream
- Get to know Reader
- Get to know Writer
Stream vs Reader and writer
Java's stream-based I/O is built upon four abstract classes:
InputStream, OutputStream,
Reader, and Writer.
They are used to create several concrete stream subclasses.
InputStream and OutputStream are designed for byte streams.
Reader and Writer are designed for character streams.
The byte stream classes and the character stream classes form separate hierarchies.
You use the character stream classes when working with characters or strings. You use the byte stream classes when working with bytes or other binary objects.
InputStream
The byte stream classes handles byte-oriented I/O.
The byte stream classes are topped by InputStream and OutputStream.
InputStream is an abstract class that defines Java's model of streaming byte input.
It implements the Closeable interface.
Most of the methods in this class will throw an IOException on error conditions.
InputStream has the following methods.
int available( )
Returns the number of bytes available for reading.void close( )
Closes the input source.void mark(int numBytes)
Places a mark at the current point that will remain valid until numBytes bytes are read.boolean markSupported( )
Returns true if mark( )/reset( ).int read( )
Returns an integer representation of the next available byte of input. -1 is returned if file ends.int read(byte buffer[ ])
Read up to buffer.length bytes into buffer and returns the actual number of bytes that were successfully read. -1 is returned when the end of the file is encountered.int read(byte buffer[ ], int offset, int numBytes)
Read up to numBytes bytes into buffer starting at buffer[offset], returning the number of bytes successfully read. -1 is returned when the end of the file is encountered.void reset( )
Resets the input pointer to the previously set mark.long skip(long numBytes)
Skip numBytes bytes of input, returning the number of bytes actually ignored.
OutputStream
OutputStream is an abstract class that defines streaming byte output.
It implements the Closeable and Flushable interfaces.
Methods from OutputStream:
void close( )Closes the output stream.void flush( )Flushes the output state so that any buffers are cleared.void write(int b)Writes a single byte to an output stream.void write(byte buffer[ ])Writes a complete array of bytes to an output stream.void write(byte buffer[ ], int offset, int numBytes)Writes a subrange of numBytes bytes from the array buffer, beginning at buffer[offset].
Reader
The Character Streams include direct I/O support for characters. At the top of the character stream hierarchies are the Reader and Writer abstract classes.
Reader is an abstract class that defines Java's model of streaming character input.
It implements the Closeable and Readable interfaces.
Methods from Reader:
abstract void close( )Closes the input source.void mark(int numChars)Places a mark at the current point that will remain valid until numChars characters are read.boolean markSupported( )Returns true if mark( )/reset( ) are supported.int read( )Returns an integer representation of the next available character. -1 is returned when the end of the file is encountered.int read(char buffer[ ])Reads up to buffer.length characters into buffer and returns the actual number of characters that were successfully read. -1 is returned when the end of the file is encountered.abstract int read(char buffer[ ], int offset, int numChars)Reads up to numChars characters into buffer starting at buffer[offset], returning the number of characters successfully read. -1 is returned when the end of the file is encountered.boolean ready( )Returns true if the next input request is ready.void reset( )Resets the input pointer to the previously set mark.long skip(long numChars)Skips numChars characters of input, returning the number of characters actually skipped.
Writer
Writer is an abstract class that defines streaming character output.
It implements the Closeable, Flushable, and Appendable interfaces.
Methods from Writer:
Writer append(char ch)Writes ch to the writer.Writer append(CharSequence chars)Writes chars to the end.Writer append(CharSequence chars, int begin, int end)Writes the subrange of chars specified by begin and end-1.abstract void close( )Closes the output stream.abstract void flush( )Flushes the output buffers.void write(int ch)Writes a single character to the output stream.void write(char buffer[ ])Writes a complete array of characters to the output stream.abstract void write(char buffer[ ], int offset, int numChars)Writes a subrange of numChars characters from the array buffer, beginning at buffer[offset] to the invoking output stream.void write(String str)Writes str to the invoking output stream.void write(String str, int offset, int numChars)Writes a subrange of numChars characters from the string str, beginning at the specified offset.
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