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Java™ Platform Standard Ed. 6 |
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java.lang.Object java.io.InputStream java.io.FilterInputStream
public class FilterInputStream
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. |
Constructor Summary | |
---|---|
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. |
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. |
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)
Reads up to byte.length bytes of data from this
input stream into an array of bytes. |
int |
read(byte[] b,
int off,
int len)
Reads up to len bytes of data from this input stream
into an array of bytes. |
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 this input
stream. |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
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protected volatile InputStream in
Constructor Detail |
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protected FilterInputStream(InputStream in)
FilterInputStream
by assigning the argument in
to the field this.in
so as
to remember it for later use.
in
- the underlying input stream, or null
if
this instance is to be created without an underlying stream.Method Detail |
---|
public int read() throws IOException
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.
read
in class InputStream
-1
if the end of the
stream is reached.
IOException
- if an I/O error occurs.in
public int read(byte[] b) throws IOException
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.
read
in class InputStream
b
- the buffer into which the data is read.
-1
if there is no more data because the end of
the stream has been reached.
IOException
- if an I/O error occurs.read(byte[], int, int)
public int read(byte[] b, int off, int len) throws IOException
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.
read
in class InputStream
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.
-1
if there is no more data because the end of
the stream has been reached.
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.in
public long skip(long n) throws IOException
n
bytes of data from this input
stream. The skip
method may, for a variety of reasons, end
up skipping over some smaller number of bytes, possibly 0
.
This may result from any of a number of conditions; reaching end of file
before n
bytes have been skipped is only one possibility.
The actual number of bytes skipped is returned. If n
is
negative, no bytes are skipped.
The skip
method of this class creates a
byte array and then repeatedly reads into it until n
bytes
have been read or the end of the stream has been reached. Subclasses are
encouraged to provide a more efficient implementation of this method.
For instance, the implementation may depend on the ability to seek.
This method simply performs in.skip(n)
.
skip
in class InputStream
n
- the number of bytes to be skipped.
IOException
- if the stream does not support seek,
or if some other I/O error occurs.public int available() throws IOException
This method returns the result of in
.available().
available
in class InputStream
IOException
- if an I/O error occurs.public void close() throws IOException
in.close()
.
close
in interface Closeable
close
in class InputStream
IOException
- if an I/O error occurs.in
public void mark(int readlimit)
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)
.
mark
in class InputStream
readlimit
- the maximum limit of bytes that can be read before
the mark position becomes invalid.in
,
reset()
public void reset() throws IOException
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.
reset
in class InputStream
IOException
- if the stream has not been marked or if the
mark has been invalidated.in
,
mark(int)
public boolean markSupported()
mark
and reset
methods.
This method
simply performs in.markSupported()
.
markSupported
in class InputStream
true
if this stream type supports the
mark
and reset
method;
false
otherwise.in
,
InputStream.mark(int)
,
InputStream.reset()
|
Java™ Platform Standard Ed. 6 |
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