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.
Field Summary
protected InputStream | in | The input stream to be filtered. |
Protected Constructor Summary
FilterInputStream(InputStream in)
Creates a
FilterInputStream
by assigning the argument in
to the field this.in so as
to remember it for later use. |
Public Method Summary
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.
|
synchronized void |
mark(int readlimit)
Marks the current position in this input stream.
|
boolean |
markSupported()
Tests if this input stream supports the
mark
and reset methods. |
int |
read()
Reads the next byte of data from this input stream.
|
int |
read(byte[] b, int off, int len)
Reads up to
len bytes of data from this input stream
into an array of bytes. |
int |
read(byte[] b)
Reads up to
byte.length bytes of data from this
input stream into an array of bytes. |
synchronized void |
reset()
Repositions this stream to the position at the time the
mark method was last called on this input stream. |
long |
skip(long n)
Skips over and discards
n bytes of data from the
input stream. |
Inherited Method Summary
Fields
Protected Constructors
protected 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 | the underlying input stream, or null if
this instance is to be created without an underlying stream.
|
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Public Methods
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 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
- 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. |
---|
public 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
public synchronized 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 | the maximum limit of bytes that can be read before the mark position becomes invalid. |
---|
public boolean markSupported ()
Tests if this input stream supports the mark
and reset
methods.
This method
simply performs in.markSupported()
.
Returns
true
if this stream type supports themark
andreset
method;false
otherwise.
public 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
- 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
public 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 | the buffer into which the data is read. |
---|---|
off | the start offset in the destination array b |
len | the maximum number of bytes read. |
Returns
- 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
public 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 | the buffer into which the data is read. |
---|
Returns
- 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
public synchronized 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. |
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public 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 | the number of bytes to be skipped. |
---|
Returns
- the actual number of bytes skipped.
Throws
IOException | if the stream does not support seek, or if some other I/O error occurs. |
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