java.io
Class PushbackInputStream

java.lang.Object
  |
  +--java.io.InputStream
        |
        +--java.io.FilterInputStream
              |
              +--java.io.PushbackInputStream

public synchronized class PushbackInputStream
extends FilterInputStream


Field Summary
protected  byte[] buf
           
protected  int pos
           
 
Fields inherited from class java.io.FilterInputStream
in
 
Constructor Summary
PushbackInputStream(InputStream)
           
PushbackInputStream(InputStream, int)
           
 
Method Summary
 int available()
          Returns the number of bytes that can be read (or skipped over) from this input stream without blocking by the next caller of a method for this input stream.
 void close()
          Closes this input stream and releases any system resources associated with the stream.
 boolean markSupported()
          Tests if this input stream supports the mark and reset methods.
 int read()
          Reads the next byte of data from the input stream.
 int read(byte[], int, int)
          Reads up to len bytes of data from the input stream into an array of bytes.
 long skip(long)
          Skips over and discards n bytes of data from this input stream.
 void unread(byte[])
           
 void unread(byte[], int, int)
           
 void unread(int)
           
 
Methods inherited from class java.io.FilterInputStream
mark, read, reset
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait
 

Field Detail

buf

protected byte[] buf

pos

protected int pos
Constructor Detail

PushbackInputStream

public PushbackInputStream(InputStream,
                           int)

PushbackInputStream

public PushbackInputStream(InputStream)
Method Detail

read

public int read()
         throws IOException
Description copied from class: InputStream
Reads the next byte of data from the 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 is thrown.

A subclass must provide an implementation of this method.

Overrides:
read in class FilterInputStream
Returns:
the next byte of data, or -1 if the end of the stream is reached.
Throws:
IOException - if an I/O error occurs.

read

public int read(byte[],
                int,
                int)
         throws IOException
Description copied from class: InputStream
Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read, possibly zero. The number of bytes actually read is returned as an integer.

This method blocks until input data is available, end of file is detected, or an exception is thrown.

If b is null, a NullPointerException is thrown.

If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown.

If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b.

The first byte read is stored into element b[off], the next one into b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k] through b[off+len-1] unaffected.

In every case, elements b[0] through b[off] and elements b[off+len] through b[b.length-1] are unaffected.

If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.

The read(b, off, len) method for class InputStream simply calls the method read() repeatedly. If the first such call results in an IOException, that exception is returned from the call to the read(b, off, len) method. If any subsequent call to read() results in a IOException, the exception is caught and treated as if it were end of file; the bytes read up to that point are stored into b and the number of bytes read before the exception occurred is returned. Subclasses are encouraged to provide a more efficient implementation of this method.

Overrides:
read in class FilterInputStream
Parameters:
- the buffer into which the data is read.
- the start offset in array b at which the data is written.
- the maximum number of bytes to read.
Returns:
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.
Throws:
IOException - if an I/O error occurs.
See Also:
InputStream.read()

unread

public void unread(int)
            throws IOException
IOException

unread

public void unread(byte[],
                   int,
                   int)
            throws IOException
IOException

unread

public void unread(byte[])
            throws IOException
IOException

available

public int available()
              throws IOException
Description copied from class: InputStream
Returns the number of bytes that can be read (or skipped over) from this input stream without blocking by the next caller of a method for this input stream. The next caller might be the same thread or or another thread.

The available method for class InputStream always returns 0.

This method should be overridden by subclasses.

Overrides:
available in class FilterInputStream
Returns:
the number of bytes that can be read from this input stream without blocking.
Throws:
IOException - if an I/O error occurs.

skip

public long skip(long)
          throws IOException
Description copied from class: InputStream
Skips over and discards 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. This may result from any of a number of conditions; reaching end of file before n bytes have been skipped is only one possibility. The actual number of bytes skipped is returned. If n is negative, no bytes are skipped.

The skip method of InputStream creates a byte array and then repeatedly 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.

Overrides:
skip in class FilterInputStream
Parameters:
- the number of bytes to be skipped.
Returns:
the actual number of bytes skipped.
Throws:
IOException - if an I/O error occurs.

markSupported

public boolean markSupported()
Description copied from class: InputStream
Tests if this input stream supports the mark and reset methods. The markSupported method of InputStream returns false.

Overrides:
markSupported in class FilterInputStream
Returns:
true if this true type supports the mark and reset method; false otherwise.
See Also:
InputStream.mark(int), InputStream.reset()

close

public void close()
           throws IOException
Description copied from class: InputStream
Closes this input stream and releases any system resources associated with the stream.

The close method of InputStream does nothing.

Overrides:
close in class FilterInputStream
Throws:
IOException - if an I/O error occurs.