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Object | +----java.io.InputStream
Applications that need to define a subclass of
InputStream
must always provide a method that returns
the next byte of input.
mark
and reset
methods.
b.length
bytes of data from this input
stream into an array of bytes.
len
bytes of data from this input stream
into an array of bytes.
mark
method was last called on this input stream.
n
bytes of data from this
input stream.
public InputStream()
public int available() throws IOException
InputStream
returns 0
. This method
should be overridden by subclasses.
public void close() throws IOException
The close
method of InputStream
does nothing.
public synchronized 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
arguments tells this input stream to
allow that many bytes to be read before the mark position gets
invalidated.
The mark
method of InputStream
does nothing.
public boolean markSupported()
mark
and reset
methods. The markSupported
method of InputStream
returns false
.
true
if this true type supports the mark and reset
method; false
otherwise.
public abstract 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.
A subclass must provide an implementation of this method.
-1
if the end of the
stream is reached.
public int read(byte b) throws IOException
b.length
bytes of data from this input
stream into an array of bytes.
The read
method of InputStream
calls
the read
method of three arguments with the arguments
b
, 0
, and b.length
.
-1
is there is no more data because the end of
the stream has been reached.
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. If the argument b
is null
, a
NullPointerException
is thrown.
The read
method of InputStream
reads a
single byte at a time using the read method of zero arguments to
fill in the array. Subclasses are encouraged to provide a more
efficient implementation of this method.
-1
if there is no more data because the end of
the stream has been reached.
public synchronized void reset() throws IOException
mark
method was last called on this input stream.
The reset
method of InputStream
throws
an IOException
, because input streams, by default, do
not support mark
and 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 parser, it just chugs along happily. If the stream is not of that type, the parser should toss an exception when it fails, which, if it happens within readlimit bytes, allows the outer code to reset the stream and try another parser.
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
. The actual number of bytes skipped is
returned.
The skip
method of InputStream
creates
a byte array of length n
and then 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.
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