FilterInputStream

The source input stream that is filtered.

Constructs a new FilterInputStream with 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.

Returns an estimated number of bytes that can be read or skipped without blocking for more input.

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, 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 racy).

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 available.

Closes this stream. This implementation closes the filtered stream.

Sets a mark position in this stream. The parameter readlimit indicates how many bytes can be read before the mark is invalidated. Sending reset() will reposition this stream back to the marked position, provided that readlimit has not been surpassed.

This implementation sets a mark in the filtered stream.

Indicates whether this stream supports mark() and reset() . This implementation returns whether or not the filtered stream supports marking.

Reads a single byte from the filtered stream and returns it as an integer in the range from 0 to 255. Returns -1 if the end of this stream has been reached.

Reads up to byteCount bytes from this stream and stores them in the byte array buffer starting at byteOffset . Returns the number of bytes actually read or -1 if the end of the stream has been reached.

Resets this stream to the last marked location. This implementation resets the target stream.

Skips byteCount bytes in this stream. Subsequent calls to read will not return these bytes unless reset is used. This implementation skips byteCount bytes in the filtered stream.