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FILE
HANDLING (STREAM)
Streams in File Handling.
All the Java Program can be pass through Input/Output (I/O)
streams. A stream is an abstraction that either Consumer or Produces
information, linked to a physical device by the Java I/O system. In java an
object from which, read and write a sequence of bytes is called an
input stream
and an output stream respectively,
specified in the abstract classes
InputStream and
OutputStream.
Streams also support different kind of data, including simple bytes, primitive
data types, localized characters, and objects.
The
byte-oriented streams are inconvenient/ difficult
for processing information stored in Unicode (recall that Unicode uses
two bytes per character),
there is a separate hierarchy of classes for processing Unicode characters that
inherit from the abstract Reader and
Writer classes.
These classes have read and write operations that are based on 2-byte Unicode
characters rather than on single-byte characters.
Overview of I/O
within the Java.
Java I/O can be summarized as
follows:
- In Java two kinds of stream use- 1) 8-bits
stream introduce in Java 1.0 version, and 2) 16-bits stream introduce in
Java 1.1 version, to over come limitation like did not support internationalized
character sets (e.g Hindi, Korean , Chinese, Japanese,
etc).
- The 8-bits Stream are types of InputStream
or OutputStream
and 16-bits Stream are types of
Reader (input) and Writer
(output).
- All I/O file in java is passing through
using stream.
- Each stream offer one types of I/O service
( e.g. Binary I/O, Character I/O, byte array I/O, file I/O, etc).
Byte Streams and Character
Streams.
In java language,
two type of stream is define- byte and character streams-
- Byte Streams-
Byte Streams provide a standard/ convenient means for
handling input or output (I/O) of streams. Generally, used for writing or
reading of binary data.
- Character Streams-
Character Streams provide
a standard/ convenient means for handling input and output (I/O) of
characters. Generally, used for handle Unicode (encode data) data and in
some case, character streams are more efficient than byte streams.
Bridging the gap
between Byte and character stream-- Stream classes java.io.InputStreamReader and java.io.OutputStreamWriter
able to provide the bridge to the gap between them.
The main purpose of these classes is to convert the byte data into character
data according to the specific encoding or platform default.
/*
* Syntax for Bridging the gap between the Byte and character stream
*/
package r4r.co.in;
class r4r
{
public static void main(String[] args)
{
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Insert input String!");
String string = reader.readLine();
}
}
Streams classes.
Streams I/O
classes are belongs to java.io package and are of two types such as-
-
Top level
abstract classes- Abstract
Reader and
Writer classes
are parent classes for character-stream based classes in the java.io
package. Reader classes are used to read 16-bit character streams
and Writer classes are also used to write to 16-bit character
streams.
java.io.Reader and java.io.Writer
are top level classes contain following method for reading and writing to
streams.
Method of java.io.Reader/ InputStream-
- abstract int read()- use for reading
the next byte of data from the input stream.
- int read(char cbuf[])- use for reading
the bytes from the stream and stores them in cbuf[]
array .
- int read(char cbuf[], int offset,
int length)-use for reading
upto length bytes of data from the input
stream into an array of bytes.
- void close()- use for closes
this input stream and releases all the system resources that associated
with the stream.
Method of java.io.Writer
/OutputStream-
- int write(int c)-
- int write(char cbuf[])- Use for writes cbuf[]
from the specified byte array to this output stream.
- int write(char cbuf[], int offset,
int length)-Use for writes length bytes from the specified byte
array starting at offset to this output stream.
- void flush()- use for flushes
this output stream and forces any buffered output bytes to be written
out.
- void close()- use for closes
this input stream and releases all the system resources that associated
with the stream.
- Descendant
implementation classes- Specialized Descendent Stream Classes are the subclass of Top level classes,
provide additional functionality. All the Specialized classes is extend their parent classes.
Use the syntax, the BufferedReader
class not only provides buffered reading for efficiency but also provides
methods such as 'readLine()'
to read a line of input in serialization manner.
BufferedReader
reader = new
BufferedReader(new
InputStreamReader(System.in));
String string = reader.readLine();
The
Specialized classes also belongs to java.io package like -
- BufferedReader
- FileReader
- StringReader
- LineNumberReader
- FilterReader
- PushbackReader
- InputStreamReader
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