BufferedInputStream
public
class
BufferedInputStream
extends FilterInputStream
java.lang.Object | |||
↳ | java.io.InputStream | ||
↳ | java.io.FilterInputStream | ||
↳ | java.io.BufferedInputStream |
A BufferedInputStream
adds
functionality to another input stream-namely,
the ability to buffer the input and to
support the mark
and reset
methods. 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 and the reset
operation
causes all the bytes read since the most
recent mark
operation to be
reread before new bytes are taken from
the contained input stream.
Summary
Fields | |
---|---|
protected
byte[] |
buf
The internal buffer array where the data is stored. |
protected
int |
count
The index one greater than the index of the last valid byte in the buffer. |
protected
int |
marklimit
The maximum read ahead allowed after a call to the
|
protected
int |
markpos
The value of the |
protected
int |
pos
The current position in the buffer. |
Inherited fields |
---|
Public constructors | |
---|---|
BufferedInputStream(InputStream in)
Creates a |
|
BufferedInputStream(InputStream in, int size)
Creates a |
Public methods | |
---|---|
int
|
available()
Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. |
void
|
close()
Closes this input stream and releases any system resources associated with the stream. |
void
|
mark(int readlimit)
See the general contract of the |
boolean
|
markSupported()
Tests if this input stream supports the |
int
|
read()
See
the general contract of the |
int
|
read(byte[] b, int off, int len)
Reads bytes from this byte-input stream into the specified byte array, starting at the given offset. |
void
|
reset()
See the general contract of the |
long
|
skip(long n)
See the general contract of the |
Inherited methods | |
---|---|
Fields
buf
protected byte[] buf
The internal buffer array where the data is stored. When necessary, it may be replaced by another array of a different size.
count
protected int count
The index one greater than the index of the last valid byte in
the buffer.
This value is always
in the range 0
through buf.length
;
elements buf[0]
through buf[count-1]
contain buffered input data obtained
from the underlying input stream.
marklimit
protected int marklimit
The maximum read ahead allowed after a call to the
mark
method before subsequent calls to the
reset
method fail.
Whenever the difference between pos
and markpos
exceeds marklimit
,
then the mark may be dropped by setting
markpos
to -1
.
markpos
protected int markpos
The value of the pos
field at the time the last
mark
method was called.
This value is always
in the range -1
through pos
.
If there is no marked position in the input
stream, this field is -1
. If
there is a marked position in the input
stream, then buf[markpos]
is the first byte to be supplied as input
after a reset
operation. If
markpos
is not -1
,
then all bytes from positions buf[markpos]
through buf[pos-1]
must remain
in the buffer array (though they may be
moved to another place in the buffer array,
with suitable adjustments to the values
of count
, pos
,
and markpos
); they may not
be discarded unless and until the difference
between pos
and markpos
exceeds marklimit
.
pos
protected int pos
The current position in the buffer. This is the index of the next
character to be read from the buf
array.
This value is always in the range 0
through count
. If it is less
than count
, then buf[pos]
is the next byte to be supplied as input;
if it is equal to count
, then
the next read
or skip
operation will require more bytes to be
read from the contained input stream.
See also:
Public constructors
BufferedInputStream
public BufferedInputStream (InputStream in)
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 |
InputStream : the underlying input stream. |
BufferedInputStream
public BufferedInputStream (InputStream in, int size)
Creates a BufferedInputStream
with the specified buffer size,
and saves its argument, the input stream
in
, for later use. An internal
buffer array of length size
is created and stored in buf
.
Parameters | |
---|---|
in |
InputStream : the underlying input stream. |
size |
int : the buffer size. |
Throws | |
---|---|
IllegalArgumentException |
if size <= 0 . |
Public methods
available
public int available ()
Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. The next invocation might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.
This method returns the sum of the number of bytes remaining to be read in
the buffer (count - pos
) and the result of calling the
in
.available()
.
Returns | |
---|---|
int |
an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking. |
Throws | |
---|---|
IOException |
if this input stream has been closed by
invoking its close() method,
or an I/O error occurs. |
close
public void close ()
Closes this input stream and releases any system resources associated with the stream. Once the stream has been closed, further read(), available(), reset(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect.
Throws | |
---|---|
IOException |
if an I/O error occurs. |
mark
public void mark (int readlimit)
See the general contract of the mark
method of InputStream
.
Parameters | |
---|---|
readlimit |
int : the maximum limit of bytes that can be read before
the mark position becomes invalid. |
See also:
markSupported
public boolean markSupported ()
Tests if this input stream supports the mark
and reset
methods. The markSupported
method of BufferedInputStream
returns
true
.
Returns | |
---|---|
boolean |
a boolean indicating if this stream type supports
the mark and reset methods. |
See also:
read
public int read ()
See
the general contract of the read
method of InputStream
.
Returns | |
---|---|
int |
the next byte of data, or -1 if the end of the
stream is reached. |
Throws | |
---|---|
IOException |
if this input stream has been closed by
invoking its close() method,
or an I/O error occurs. |
See also:
read
public int read (byte[] b, int off, int len)
Reads bytes from this byte-input stream into the specified byte array, starting at the given offset.
This method implements the general contract of the corresponding
read
method of
the InputStream
class. As an additional
convenience, it attempts to read as many bytes as possible by repeatedly
invoking the read
method of the underlying stream. This
iterated read
continues until one of the following
conditions becomes true:
- The specified number of bytes have been read,
- The
read
method of the underlying stream returns-1
, indicating end-of-file, or - The
available
method of the underlying stream returns zero, indicating that further input requests would block.
read
on the underlying stream returns
-1
to indicate end-of-file then this method returns
-1
. Otherwise this method returns the number of bytes
actually read.
Subclasses of this class are encouraged, but not required, to attempt to read as many bytes as possible in the same fashion.
Parameters | |
---|---|
b |
byte : destination buffer. |
off |
int : offset at which to start storing bytes. |
len |
int : maximum number of bytes to read. |
Returns | |
---|---|
int |
the number of bytes read, or -1 if the end of
the stream has been reached. |
Throws | |
---|---|
IOException |
if this input stream has been closed by
invoking its close() method,
or an I/O error occurs. |
reset
public void reset ()
See the general contract of the reset
method of InputStream
.
If markpos
is -1
(no mark has been set or the mark has been
invalidated), an IOException
is thrown. Otherwise, pos
is
set equal to markpos
.
Throws | |
---|---|
IOException |
if this stream has not been marked or,
if the mark has been invalidated, or the stream
has been closed by invoking its close()
method, or an I/O error occurs. |
See also:
skip
public long skip (long n)
See the general contract of the skip
method of InputStream
.
Parameters | |
---|---|
n |
long : the number of bytes to be skipped. |
Returns | |
---|---|
long |
the actual number of bytes skipped. |
Throws | |
---|---|
IOException |
if this input stream has been closed by
invoking its close() method,
in.skip(n) throws an IOException,
or an I/O error occurs. |