Class FilterInputStream
- java.lang.Object
-
- java.io.InputStream
-
- java.io.FilterInputStream
- All Implemented Interfaces:
-
Closeable
,AutoCloseable
- Direct Known Subclasses:
-
BufferedInputStream
,CheckedInputStream
,CipherInputStream
,DataInputStream
,DeflaterInputStream
,DigestInputStream
,InflaterInputStream
,LineNumberInputStream
,ProgressMonitorInputStream
,PushbackInputStream
public class FilterInputStream extends InputStream
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.
- Since:
- 1.0
Field Summary
Modifier and Type | Field | Description |
---|---|---|
protected InputStream | in | The input stream to be filtered. |
Constructor Summary
Modifier | Constructor | Description |
---|---|---|
protected | FilterInputStream(InputStream in) | Creates a |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
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 |
int | read() | Reads the next byte of data from this input stream. |
int | read(byte[] b) | Reads up to |
int | read(byte[] b,
int off,
int len) | Reads up to |
void | reset() | Repositions this stream to the position at the time the |
long | skip(long n) | Skips over and discards |
Methods declared in class java.io.InputStream
nullInputStream, readAllBytes, readNBytes, readNBytes, transferTo
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Field Detail
in
protected volatile InputStream in
The input stream to be filtered.
Constructor Detail
FilterInputStream
protected 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
- the underlying input stream, ornull
if this instance is to be created without an underlying stream.
Method Detail
read
public int read() throws IOException
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.
- Specified by:
-
read
in classInputStream
- Returns:
- 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:
in
read
public int read(byte[] b) throws IOException
Reads up to b.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.
- Overrides:
-
read
in classInputStream
- Parameters:
-
b
- the buffer into which the data is 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:
read(byte[], int, int)
read
public int read(byte[] b, int off, int len) throws IOException
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.
- Overrides:
-
read
in classInputStream
- Parameters:
-
b
- the buffer into which the data is read. -
off
- the start offset in the destination arrayb
-
len
- the maximum number of bytes 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:
-
NullPointerException
- Ifb
isnull
. -
IndexOutOfBoundsException
- Ifoff
is negative,len
is negative, orlen
is greater thanb.length - off
-
IOException
- if an I/O error occurs. - See Also:
in
skip
public long skip(long n) throws IOException
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)
.
- Overrides:
-
skip
in classInputStream
- Parameters:
-
n
- the number of bytes to be skipped. - Returns:
- the actual number of bytes skipped.
- Throws:
-
IOException
- ifin.skip(n)
throws an IOException.
available
public int available() throws IOException
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().
- Overrides:
-
available
in classInputStream
- Returns:
- 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
public void close() throws IOException
Closes this input stream and releases any system resources associated with the stream. This method simply performs in.close()
.
- Specified by:
-
close
in interfaceAutoCloseable
- Specified by:
-
close
in interfaceCloseable
- Overrides:
-
close
in classInputStream
- Throws:
-
IOException
- if an I/O error occurs. - See Also:
in
mark
public 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)
.
- Overrides:
-
mark
in classInputStream
- Parameters:
-
readlimit
- the maximum limit of bytes that can be read before the mark position becomes invalid. - See Also:
-
in
,reset()
reset
public void reset() throws IOException
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.
- Overrides:
-
reset
in classInputStream
- Throws:
-
IOException
- if the stream has not been marked or if the mark has been invalidated. - See Also:
-
in
,mark(int)
markSupported
public boolean markSupported()
Tests if this input stream supports the mark
and reset
methods. This method simply performs in.markSupported()
.
- Overrides:
-
markSupported
in classInputStream
- Returns:
-
true
if this stream type supports themark
andreset
method;false
otherwise. - See Also:
-
in
,InputStream.mark(int)
,InputStream.reset()