to top

Summary: Fields | Protected Ctors | Methods | Inherited Methods | [Expand All]

Since: API Level 1

public class

FilterInputStream

extends InputStream

java.lang.Object
↳	java.io.InputStream
	↳	java.io.FilterInputStream

Known Direct Subclasses

Base64InputStream, BufferedInputStream, CheckedInputStream, CipherInputStream, DataInputStream, DeflaterInputStream, DigestInputStream, InflaterInputStream, LineNumberInputStream, PushbackInputStream

Known Indirect Subclasses

GZIPInputStream, JarInputStream, ZipInputStream

Class Overview

Wraps an existing InputStream and 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.

Summary

Fields
protected InputStream	in	The source input stream that is filtered.

Protected Constructors
	FilterInputStream(InputStream in) Constructs a new `FilterInputStream` with the specified input stream as source.

Public Methods
int	available() Returns an estimated number of bytes that can be read or skipped without blocking for more input.
void	close() Closes this stream.
synchronized void	mark(int readlimit) Sets a mark position in this stream.
boolean	markSupported() Indicates whether this stream supports `mark()` and `reset()`.
int	read() Reads a single byte from the filtered stream and returns it as an integer in the range from 0 to 255.
int	read(byte[] buffer, int offset, int count) Reads at most `count` bytes from this stream and stores them in the byte array `buffer` starting at `offset`.
synchronized void	reset() Resets this stream to the last marked location.
long	skip(long byteCount) Skips `byteCount` bytes in this stream.

[Expand]

Inherited Methods

From class java.io.InputStream

int	available() Returns an estimated number of bytes that can be read or skipped without blocking for more input.
void	close() Closes this stream.
void	mark(int readlimit) Sets a mark position in this InputStream.
boolean	markSupported() Indicates whether this stream supports the `mark()` and `reset()` methods.
int	read(byte[] buffer) Equivalent to `read(buffer, 0, buffer.length)`.
abstract int	read() Reads a single byte from this stream and returns it as an integer in the range from 0 to 255.
int	read(byte[] buffer, int offset, int length) Reads at most `length` bytes from this stream and stores them in the byte array `b` starting at `offset`.
synchronized void	reset() Resets this stream to the last marked location.
long	skip(long byteCount) Skips at most `n` bytes in this stream.

From class java.lang.Object

Object	clone() Creates and returns a copy of this `Object`.
boolean	equals(Object o) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of `Class` that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object.
final void	wait(long millis, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.
final void	wait(long millis) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.

From interface java.io.Closeable

Fields

protected InputStream in

Since: API Level 1

The source input stream that is filtered.

Protected Constructors

protected FilterInputStream (InputStream in)

Since: API Level 1

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.

Parameters

in	the input stream to filter reads on.

Public Methods

public int available ()

Since: API Level 1

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.

Returns

the estimated number of bytes available

Throws

IOException

public void close ()

Since: API Level 1

Closes this stream. This implementation closes the filtered stream.

Throws

IOException	if an error occurs while closing this stream.

public synchronized void mark (int readlimit)

Since: API Level 1

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.

Parameters

readlimit	the number of bytes that can be read from this stream before the mark is invalidated.

public boolean markSupported ()

Since: API Level 1

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

Returns

true if mark() and reset() are supported, false otherwise.

public int read ()

Since: API Level 1

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.

Returns

the byte read or -1 if the end of the filtered stream has been reached.

Throws

IOException	if the stream is closed or another IOException occurs.

public int read (byte[] buffer, int offset, int count)

Since: API Level 1

Reads at most count bytes from this stream and stores them in the byte array buffer starting at 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.

Parameters

buffer	the byte array in which to store the bytes read.
offset	the initial position in `buffer` to store the bytes read from this stream.
count	the maximum number of bytes to store in `buffer`.

Returns

the number of bytes actually read or -1 if the end of the filtered stream has been reached while reading.

Throws

IOException	if this stream is closed or another I/O error occurs.

public synchronized void reset ()

Since: API Level 1

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

Throws

IOException	if this stream is already closed, no mark has been set or the mark is no longer valid because more than `readlimit` bytes have been read since setting the mark.

public long skip (long byteCount)

Since: API Level 1

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.

Parameters

byteCount	the number of bytes to skip.

Returns

the number of bytes actually skipped.

Throws

IOException	if this stream is closed or another IOException occurs.

Results

Interfaces

Classes

Exceptions

Errors

FilterInputStream

Class Overview

See Also

Summary

Fields

protected InputStream in

Protected Constructors

protected FilterInputStream (InputStream in)

Parameters

Public Methods

public int available ()

Returns

Throws

public void close ()

Throws

public synchronized void mark (int readlimit)

Parameters

See Also

public boolean markSupported ()

Returns

See Also

public int read ()

Returns

Throws

public int read (byte[] buffer, int offset, int count)

Parameters

Returns

Throws

public synchronized void reset ()

Throws

See Also

public long skip (long byteCount)

Parameters

Returns

Throws

See Also