This class is an input stream filter that provides a buffer into which data
can be "unread." An application may unread data at any time by pushing it
back into the buffer, as long as the buffer has sufficient room. Subsequent
reads will read all of the pushed-back data in the buffer before reading
from the underlying input stream.
This functionality is useful when a fragment of code should read
an indefinite number of data bytes that are delimited by
particular byte values. After reading the terminating byte the
code fragment can push it back, so that the next read
operation on the input stream will re-read that byte.
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
This method returns the most recently pushed-back byte, if there is
one, and otherwise calls the read method of its underlying
input stream and returns whatever value that method returns.
the next byte of data, or -1 if the end of the
stream has been reached.
public int read(byte b,
int len) throws IOException
Reads up to len bytes of data from this input stream into
an array of bytes. This method first reads any pushed-back bytes; after
that, if fewer than than len bytes have been read then it
reads from the underlying input stream. This method blocks until at
least 1 byte of input is available.
b - the buffer into which the data is read.
off - the start offset of the data.
len - the maximum number of bytes read.
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.
public void unread(byte b,
int len) throws IOException
Pushes back a portion of an array of bytes by copying it to the front
of the pushback buffer. After this method returns, the next byte to be
read will have the value b[off], the byte after that will
have the value b[off+1], and so forth.
Pushes back an array of bytes by copying it to the front of the
pushback buffer. After this method returns, the next byte to be read
will have the value b, the byte after that will have the
value b, and so forth.
Returns the number of bytes that can be read from this input stream
without blocking. This method calls the available method
of the underlying input stream; it returns that value plus the number of
bytes that have been pushed back.
the number of bytes that can be read from the input stream
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