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java.lang.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.
InputStream()
available()
close()
mark(int)
markSupported()
mark
and reset methods.
read()
read(byte[])
b.length bytes of data from this input
stream into an array of bytes.
read(byte[], int, int)
len bytes of data from this input stream
into an array of bytes.
reset()
mark method was last called on this input stream.
skip(long)
n bytes of data from this
input stream.
InputStream
public InputStream()
read
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.
read
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.
read
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 first argument is null, up to
len bytes are read and discarded.
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.
skip
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.
available
public int available() throws IOException
InputStream returns 0. This method
should be overridden by subclasses.
close
public void close() throws IOException
The close method of InputStream does nothing.
mark
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.
reset
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.
markSupported
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.
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