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Java Platform 1.2 |
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java.lang.Object
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+--java.io.InputStream
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+--java.io.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 the number of bytes that can be read from this input stream without blocking. |
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 the
input stream. |
| Methods inherited from class java.lang.Object |
clone,
equals,
finalize,
getClass,
hashCode,
notify,
notifyAll,
toString,
wait,
wait,
wait |
| Field Detail |
protected InputStream in
| Constructor Detail |
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.
-1 if the end of the
stream is reached.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.
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.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. This method blocks until some input is
available.
This method simply performs in.read(b, off, len)
and returns the result.
b - the buffer into which the data is read.off - the start offset of the data.len - the maximum number of bytes read.-1 if there is no more data because the end of
the stream has been reached.in
public long skip(long n)
throws IOException
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).
n - the number of bytes to be skipped.
public int available()
throws IOException
This method
simply performs in.available(n) and
returns the result.
in
public void close()
throws IOException
in.close().inpublic 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).
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.
in,
mark(int)public boolean markSupported()
mark
and reset methods.
This method
simply performs in.markSupported().true if this stream type supports the
mark and reset method;
false otherwise.in,
InputStream.mark(int),
InputStream.reset()
|
Java Platform 1.2 |
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