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Added in API level 1

FilterInputStream

public class FilterInputStream
extends InputStream

java.lang.Object
   ↳ java.io.InputStream
     ↳ java.io.FilterInputStream
Known Direct Subclasses
Known Indirect Subclasses


A FilterInputStream contains some other input stream, which it uses as its basic source of data, possibly transforming the data along the way or providing additional functionality. The class FilterInputStream itself simply overrides all methods of InputStream with versions that pass all requests to the contained input stream. Subclasses of FilterInputStream may further override some of these methods and may also provide additional methods and fields.

Summary

Fields

protected InputStream in

The input stream to be filtered.

Protected constructors

FilterInputStream(InputStream in)

Creates a FilterInputStream by assigning the argument in to the field this.in so as to remember it for later use.

Public methods

int available()

Returns an estimate of 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.

void mark(int readlimit)

Marks the current position in this input stream.

boolean markSupported()

Tests if this input stream supports the mark and reset methods.

int read()

Reads the next byte of data from this input stream.

int read(byte[] b, int off, int len)

Reads up to len bytes of data from this input stream into an array of bytes.

int read(byte[] b)

Reads up to byte.length bytes of data from this input stream into an array of bytes.

void reset()

Repositions this stream to the position at the time the mark method was last called on this input stream.

long skip(long n)

Skips over and discards n bytes of data from the input stream.

Inherited methods

From class java.io.InputStream
From class java.lang.Object
From interface java.io.Closeable
From interface java.lang.AutoCloseable

Fields

in

Added in API level 1
InputStream in

The input stream to be filtered.

Protected constructors

FilterInputStream

Added in API level 1
FilterInputStream (InputStream in)

Creates a FilterInputStream by assigning the argument in to the field this.in so as to remember it for later use.

Parameters
in InputStream: the underlying input stream, or null if this instance is to be created without an underlying stream.

Public methods

available

Added in API level 1
int available ()

Returns an estimate of 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 another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.

This method returns the result of in.available().

Returns
int an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking.
Throws
IOException if an I/O error occurs.

close

Added in API level 1
void close ()

Closes this input stream and releases any system resources associated with the stream. This method simply performs in.close().

Throws
IOException if an I/O error occurs.

See also:

mark

Added in API level 1
void mark (int readlimit)

Marks the current position in this input stream. A subsequent call to the reset method repositions this stream at the last marked position so that subsequent reads re-read the same bytes.

The readlimit argument tells this input stream to allow that many bytes to be read before the mark position gets invalidated.

This method simply performs in.mark(readlimit).

Parameters
readlimit int: the maximum limit of bytes that can be read before the mark position becomes invalid.

See also:

markSupported

Added in API level 1
boolean markSupported ()

Tests if this input stream supports the mark and reset methods. This method simply performs in.markSupported().

Returns
boolean true if this stream type supports the mark and reset method; false otherwise.

See also:

read

Added in API level 1
int read ()

Reads the next byte of data from this 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.

This method simply performs in.read() and returns the result.

Returns
int the next byte of data, or -1 if the end of the stream is reached.
Throws
IOException if an I/O error occurs.

See also:

read

Added in API level 1
int read (byte[] b, 
                int off, 
                int len)

Reads up to len bytes of data from this input stream into an array of bytes. If len is not zero, the method blocks until some input is available; otherwise, no bytes are read and 0 is returned.

This method simply performs in.read(b, off, len) and returns the result.

Parameters
b byte: the buffer into which the data is read.
off int: the start offset in the destination array b
len int: the maximum number of bytes read.
Returns
int 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
NullPointerException If b is null.
IndexOutOfBoundsException If off is negative, len is negative, or len is greater than b.length - off
IOException if an I/O error occurs.

See also:

read

Added in API level 1
int read (byte[] b)

Reads up to byte.length bytes of data from this input stream into an array of bytes. This method blocks until some input is available.

This method simply performs the call read(b, 0, b.length) and returns the result. It is important that it does not do in.read(b) instead; certain subclasses of FilterInputStream depend on the implementation strategy actually used.

Parameters
b byte: the buffer into which the data is read.
Returns
int 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:

reset

Added in API level 1
void reset ()

Repositions this stream to the position at the time the mark method was last called on this input stream.

This method simply performs in.reset().

Stream marks are intended to be used in situations where you need to read ahead a little to see what's in the stream. Often this is most easily done by invoking some general parser. If the stream is of the type handled by the parse, it just chugs along happily. If the stream is not of that type, the parser should toss an exception when it fails. If this happens within readlimit bytes, it allows the outer code to reset the stream and try another parser.

Throws
IOException if the stream has not been marked or if the mark has been invalidated.

See also:

skip

Added in API level 1
long skip (long n)

Skips over and discards n bytes of data from the input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. The actual number of bytes skipped is returned.

This method simply performs in.skip(n).

Parameters
n long: the number of bytes to be skipped.
Returns
long the actual number of bytes skipped.
Throws
IOException if the stream does not support seek, or if some other I/O error occurs.
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