public
class
FilterInputStream
extends InputStream
java.lang.Object | ||
↳ | java.io.InputStream | |
↳ | java.io.FilterInputStream |
Known Direct Subclasses |
Known Indirect Subclasses |
A FilterInputStream
contains
some other input stream, which it uses as
its basic source of data, possibly transforming
the data along the way or providing additional
functionality. The class FilterInputStream
itself simply overrides all methods of
InputStream
with versions that
pass all requests to the contained input
stream. Subclasses of FilterInputStream
may further override some of these methods
and may also provide additional methods
and fields.
Fields | |
---|---|
protected
InputStream |
in
The input stream to be filtered. |
Protected constructors | |
---|---|
FilterInputStream(InputStream in)
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 caller 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)
Marks the current position in this input stream. |
boolean
|
markSupported()
Tests if this input stream supports the |
int
|
read()
Reads the next byte of data from this input stream. |
int
|
read(byte[] b, int off, int len)
Reads up to |
int
|
read(byte[] b)
Reads up to |
void
|
reset()
Repositions this stream to the position at the time the
|
long
|
skip(long n)
Skips over and discards |
Inherited methods | |
---|---|
From
class
java.io.InputStream
| |
From
class
java.lang.Object
| |
From
interface
java.io.Closeable
| |
From
interface
java.lang.AutoCloseable
|
FilterInputStream (InputStream in)
Creates a FilterInputStream
by assigning the argument in
to the field this.in
so as
to remember it for later use.
Parameters | |
---|---|
in |
InputStream :
the underlying input stream, or null if
this instance is to be created without an underlying stream.
|
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 caller of a method for this input stream. The next caller 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 result of 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 an I/O error occurs. |
void close ()
Closes this input stream and releases any system resources
associated with the stream.
This
method simply performs in.close()
.
Throws | |
---|---|
IOException |
if an I/O error occurs. |
See also:
void mark (int readlimit)
Marks the current position in this input stream. A subsequent
call to the reset
method repositions this stream at
the last marked position so that subsequent reads re-read the same bytes.
The readlimit
argument tells this input stream to
allow that many bytes to be read before the mark position gets
invalidated.
This method simply performs in.mark(readlimit)
.
Parameters | |
---|---|
readlimit |
int :
the maximum limit of bytes that can be read before
the mark position becomes invalid. |
boolean markSupported ()
Tests if this input stream supports the mark
and reset
methods.
This method
simply performs in.markSupported()
.
Returns | |
---|---|
boolean |
true if this stream type supports the
mark and reset method;
false otherwise. |
int read ()
Reads the next byte of data from this input stream. The value
byte is returned as an int
in the range
0
to 255
. If no byte is available
because the end of the stream has been reached, the value
-1
is returned. This method blocks until input data
is available, the end of the stream is detected, or an exception
is thrown.
This method
simply performs in.read()
and returns the result.
Returns | |
---|---|
int |
the next byte of data, or -1 if the end of the
stream is reached. |
Throws | |
---|---|
IOException |
if an I/O error occurs. |
See also:
int read (byte[] b, int off, int len)
Reads up to len
bytes of data from this input stream
into an array of bytes. If len
is not zero, the method
blocks until some input is available; otherwise, no
bytes are read and 0
is returned.
This method simply performs in.read(b, off, len)
and returns the result.
Parameters | |
---|---|
b |
byte :
the buffer into which the data is read. |
off |
int :
the start offset in the destination array b |
len |
int :
the maximum number of bytes read. |
Returns | |
---|---|
int |
the total number of bytes read into the buffer, or
-1 if there is no more data because the end of
the stream has been reached. |
Throws | |
---|---|
NullPointerException |
If b is null . |
IndexOutOfBoundsException |
If off is negative,
len is negative, or len is greater than
b.length - off |
IOException |
if an I/O error occurs. |
See also:
int read (byte[] b)
Reads up to byte.length
bytes of data from this
input stream into an array of bytes. This method blocks until some
input is available.
This method simply performs the call
read(b, 0, b.length)
and returns
the result. It is important that it does
not do in.read(b)
instead;
certain subclasses of FilterInputStream
depend on the implementation strategy actually
used.
Parameters | |
---|---|
b |
byte :
the buffer into which the data is read. |
Returns | |
---|---|
int |
the total number of bytes read into the buffer, or
-1 if there is no more data because the end of
the stream has been reached. |
Throws | |
---|---|
IOException |
if an I/O error occurs. |
See also:
void reset ()
Repositions this stream to the position at the time the
mark
method was last called on this input stream.
This method
simply performs in.reset()
.
Stream marks are intended to be used in situations where you need to read ahead a little to see what's in the stream. Often this is most easily done by invoking some general parser. If the stream is of the type handled by the parse, it just chugs along happily. If the stream is not of that type, the parser should toss an exception when it fails. If this happens within readlimit bytes, it allows the outer code to reset the stream and try another parser.
Throws | |
---|---|
IOException |
if the stream has not been marked or if the mark has been invalidated. |
long skip (long n)
Skips over and discards n
bytes of data from the
input stream. The skip
method may, for a variety of
reasons, end up skipping over some smaller number of bytes,
possibly 0
. The actual number of bytes skipped is
returned.
This method simply performs in.skip(n)
.
Parameters | |
---|---|
n |
long :
the number of bytes to be skipped. |
Returns | |
---|---|
long |
the actual number of bytes skipped. |
Throws | |
---|---|
IOException |
if the stream does not support seek, or if some other I/O error occurs. |