java.lang.Object | +--java.io.Reader | +--java.io.FilterReader | +--java.io.PushbackReader
PushbackReader(java.io.Reader in) This method initializes a |
PushbackReader(java.io.Reader in, int bufsize) This method initializes a |
void | close() This method closes the stream and frees any associated resources. |
void | mark(int read_limit) This method throws an exception when called since this class does not support mark/reset. |
boolean | markSupported() This method returns |
int | read() This method reads an unsigned char from the input stream and returns it as an int in the range of 0-65535. |
synchronized int | read(char[] b, int offset, int len) This method read chars from a stream and stores them into a caller supplied buffer. |
boolean | ready() This method determines whether or not this stream is ready to be read. |
void | reset() This method always throws an IOException in this class because mark/reset functionality is not supported. |
long | skip(long num_chars) This method skips the specified number of chars in the stream. |
void | unread(int b) This method pushes a single char of data into the pushback buffer. |
synchronized void | unread(char[] buf) This method pushes all of the chars in the passed char array into the pushback buffer. |
synchronized void | unread(char[] b, int offset, int len) This method pushed back chars from the passed in array into the pushback buffer. |
public PushbackReader(java.io.Reader in)
PushbackReader
to read from the
specified subordinate Reader
with a default pushback buffer
size of 1.
in
- public PushbackReader(java.io.Reader in, int bufsize)
PushbackReader
to read from the
specified subordinate Reader
with the specified buffer
size
in
- The subordinate Reader
to read frombufsize
- The pushback buffer size to usepublic void close()
IOException
- If an error occurs.public void mark(int read_limit)
read_limit
- Not used.IOException
- Always thrown to indicate mark/reset not supported.public boolean markSupported()
false
to indicate that it does not support
mark/reset functionality.
false
to indicate that this class does not support mark/reset functionalitypublic int read()
This method will block until the char can be read.
IOException
- If an error occurspublic synchronized int read(char[] b, int offset, int len)
offset
into
the buffer and attempts to read len
chars. This method can
return before reading the number of chars requested. The actual number
of chars read is returned as an int. A -1 is returned to indicate the
end of the stream.
This method will block until some data can be read.
This method first reads chars from the pushback buffer in order to satisfy the read request. If the pushback buffer cannot provide all of the chars requested, the remaining chars are read from the underlying stream.
b
- The array into which the chars read should be storedoffset
- The offset into the array to start storing charslen
- The requested number of chars to readIOException
- If an error occurs.public boolean ready()
false
to indicate that the stream is not
ready, any attempt to read from the stream could (but is not
guaranteed to) block.
This stream is ready to read if there are either chars waiting to be read in the pushback buffer or if the underlying stream is ready to be read.
true
if this stream is ready to be read, false
otherwiseIOException
- If an error occurspublic void reset()
IOException
- Always thrown for this classpublic long skip(long num_chars)
This method first discards chars from the buffer, then calls the
skip
method on the underlying Reader
to
skip additional chars if necessary.
num_chars
- The requested number of chars to skipIOException
- If an error occurspublic synchronized void unread(char[] buf)
buf[0]
followed by buf[1]
, etc.
If the pushback buffer cannot hold all of the requested chars, an exception is thrown.
buf
- The char array to be pushed backIOException
- If the pushback buffer is fullpublic synchronized void unread(char[] b, int offset, int len)
buf[offset]
to buf[offset + len]
are pushed in reverse order so that the next char read from the stream
after this operation will be buf[offset]
followed by
buf[offset + 1]
, etc.
If the pushback buffer cannot hold all of the requested chars, an exception is thrown.
b
- The char array to be pushed backoffset
- The index into the array where the chars to be push startlen
- The number of chars to be pushed.IOException
- If the pushback buffer is fullpublic void unread(int b)
If the pushback buffer is full, this method throws an exception.
The argument to this method is an int
. Only the low eight bits
of this value are pushed back.
b
- The char to be pushed back, passed as an intIOException
- If the pushback buffer is full.
FilterReader
provides the ability to unread data from a stream. It maintains an internal buffer of unread data that is supplied to the next read operation. This is conceptually similar to mark/reset functionality, except that in this case the position to reset the stream to does not need to be known in advance.The default pushback buffer size one char, but this can be overridden by the creator of the stream.