public class FilterInputStream extends InputStream
InputStreamand performs some transformation on the input data while it is being read. Transformations can be anything from a simple byte-wise filtering input data to an on-the-fly compression or decompression of the underlying stream. Input streams that wrap another input stream and provide some additional functionality on top of it usually inherit from this class.
|Modifier and Type||Field and Description|
The source input stream that is filtered.
|Modifier||Constructor and Description|
Constructs a new
|Modifier and Type||Method and Description|
Returns an estimated number of bytes that can be read or skipped without blocking for more input.
Closes this stream.
Sets a mark position in this stream.
Indicates whether this stream supports
Reads a single byte from the filtered stream and returns it as an integer in the range from 0 to 255.
Reads at most
Resets this stream to the last marked location.
protected volatile InputStream in
protected FilterInputStream(InputStream in)
FilterInputStreamwith the specified input stream as source.
Warning: passing a null source creates an invalid
FilterInputStream, that fails on every method that is not
overridden. Subclasses should check for null in their constructors.
in- the input stream to filter reads on.
public int available() throws IOException
Note that this method provides such a weak guarantee that it is not very useful in practice.
Firstly, the guarantee is "without blocking for more input" rather than "without blocking": a read may still block waiting for I/O to complete — the guarantee is merely that it won't have to wait indefinitely for data to be written. The result of this method should not be used as a license to do I/O on a thread that shouldn't be blocked.
Secondly, the result is a conservative estimate and may be significantly smaller than the actual number of bytes available. In particular, an implementation that always returns 0 would be correct. In general, callers should only use this method if they'd be satisfied with treating the result as a boolean yes or no answer to the question "is there definitely data ready?".
Thirdly, the fact that a given number of bytes is "available" does not guarantee that a read or skip will actually read or skip that many bytes: they may read or skip fewer.
It is particularly important to realize that you must not use this method to
size a container and assume that you can read the entirety of the stream without needing
to resize the container. Such callers should probably write everything they read to a
ByteArrayOutputStream and convert that to a byte array. Alternatively, if you're
reading from a file,
File.length() returns the current length of the file (though
assuming the file's length can't change may be incorrect, reading a file is inherently
The default implementation of this method in
InputStream always returns 0.
Subclasses should override this method if they are able to indicate the number of bytes
public void close() throws IOException
public void mark(int readlimit)
readlimitindicates how many bytes can be read before the mark is invalidated. Sending
reset()will reposition this stream back to the marked position, provided that
readlimithas not been surpassed.
This implementation sets a mark in the filtered stream.
public boolean markSupported()
reset(). This implementation returns whether or not the filtered stream supports marking.
public int read() throws IOException
public int read(byte buffer, int offset, int count) throws IOException
countbytes from this stream and stores them in the byte array
offset. Returns the number of bytes actually read or -1 if no bytes have been read and the end of this stream has been reached. This implementation reads bytes from the filtered stream.
buffer- the byte array in which to store the bytes read.
offset- the initial position in
bufferto store the bytes read from this stream.
count- the maximum number of bytes to store in
IOException- if this stream is closed or another I/O error occurs.
public void reset() throws IOException
public long skip(long byteCount) throws IOException
byteCountbytes in this stream. Subsequent calls to
readwill not return these bytes unless
resetis used. This implementation skips
byteCountbytes in the filtered stream.