|
Java Platform 1.2 Beta 4 |
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: INNER | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
java.lang.Object | +--java.io.InputStream
Applications that need to define a subclass of
InputStream
must always provide a method that returns
the next byte of input.
BufferedInputStream
,
ByteArrayInputStream
,
DataInputStream
,
FilterInputStream
,
read()
,
OutputStream
,
PushbackInputStream
Constructor Summary | |
InputStream()
|
Method Summary | |
int | available()
Returns 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. |
abstract int | read()
Reads the next byte of data from the input stream. |
int | read(byte[] b,
int off,
int len)
Reads up to len bytes of data from the input stream
into an array of bytes.
|
int | read(byte[] b)
Reads some number of bytes from the input stream and stores them into the buffer array b . |
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 this
input stream. |
Methods inherited from class java.lang.Object | |
clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait |
Constructor Detail |
public InputStream()
Method Detail |
public abstract int read() throws IOException
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.
A subclass must provide an implementation of this method.
-1
if the end of the
stream is reached.public int read(byte[] b) throws IOException
b
. The number
of bytes actually read is returned as an
integer.
This method blocks until input
data is available, end of file is detected,
or an exception is thrown.
If b
is null
, a NullPointerException
is thrown.
If the length of b
is zero, then no bytes are read and 0
is returned; otherwise, there is an attempt
to read at least one byte. If no byte is
available because the stream is at end of
file, the value -1
is returned;
otherwise, at least one byte is read and
stored into b
.
The first
byte read is stored into element b[0]
,
the next one into b[1]
, and
so on. The number of bytes read is, at most,
equal to the length of b
. Let
k be the number of bytes actually
read; these bytes will be stored in elements
b[0]
through b[
k-1]
,
leaving elements b[
k]
through b[b.length-1]
unaffected.
If the first byte cannot be read for any
reason other than end of file, then an IOException
is thrown. In particular, an IOException
is thrown if the input stream has been closed.
The read(b)
method for
class InputStream
has the same
effect as:
read(b, 0, b.length)
b
- the buffer into which the data is read.-1
is there is no more data because the end of
the stream has been reached.read(byte[], int, int)
public int read(byte[] b, int off, int len) throws IOException
len
bytes of data from the input stream
into an array of bytes.
An attempt is made to read as many as len
bytes, but a smaller number may be read,
possibly zero. The number of bytes actually
read is returned as an integer.
This method blocks until input data is available, end of file is detected, or an exception is thrown.
If b
is null
,
a NullPointerException
is thrown.
If off
is negative, or len
is negative, or off+len
is
greater than the length of the array b
,
then an IndexOutOfBoundsException
is thrown.
If len
is zero,
then no bytes are read and 0
is returned; otherwise, there is an attempt
to read at least one byte. If no byte is
available because the stream is at end of
file, the value -1
is returned;
otherwise, at least one byte is read and
stored into b
.
The first
byte read is stored into element b[off]
,
the next one into b[off+1]
,
and so on. The number of bytes read is,
at most, equal to len
. Let
k be the number of bytes actually
read; these bytes will be stored in elements
b[off]
through b[off+
k-1]
,
leaving elements b[off+
k]
through b[off+len-1]
unaffected.
In every case, elements b[0]
through b[off]
and elements
b[off+len]
through b[b.length-1]
are unaffected.
If the first byte cannot
be read for any reason other than end of
file, then an IOException
is
thrown. In particular, an IOException
is thrown if the input stream has been closed.
The read(b,
off,
len)
method for class InputStream
simply calls the method read()
repeatedly. If the first such call results
in an IOException
, that exception
is returned from the call to the read(b,
off,
len)
method.
If any subsequent call to read()
results in a IOException
, the
exception is caught and treated as if it
were end of file; the bytes read up to that
point are stored into b
and
the number of bytes read before the exception
occurred is returned.
Subclasses are encouraged to provide a more
efficient implementation of this method.
b
- the buffer into which the data is read.
off
- the start offset of the data.
len
- the maximum number of bytes read.-1
if there is no more data because the end of
the stream has been reached.read()
public long skip(long n) throws IOException
n
bytes of data from this
input stream. The skip
method may, for a variety of
reasons, end up skipping over some smaller number of bytes,
possibly 0
.
This may result from
any of a number of conditions; reaching
end of file before n
bytes
have been skipped is only one possibility.
The actual number of bytes skipped is
returned. If n
is negative, no bytes are skipped.
The skip
method of InputStream
creates
a byte array and then repeatedly reads into it until
n
bytes have been read or the end of the stream has
been reached. Subclasses are encouraged to provide a more
efficient implementation of this method.
n
- the number of bytes to be skipped.public int available() throws IOException
The available
method for class InputStream
always returns 0
.
This method should be overridden by subclasses.
public void close() throws IOException
The close
method of InputStream
does nothing.
public void mark(int readlimit)
reset
method repositions this stream at
the last marked position so that subsequent reads re-read the same
bytes.
The readlimit
arguments tells this input stream to
allow that many bytes to be read before the mark position gets
invalidated.
The general contract of mark
is that, if the method markSupported
returns true
, the stream somehow
remembers all the bytes read after the call
to mark
and stands ready to
supply those same bytes again if and whenever
the method reset
is called.
However, the stream is not required to remember
any data at all if more than readlimit
bytes are read from the stream before reset
is called.
The mark
method of InputStream
does nothing.
readlimit
- the maximum limit of bytes that can be read before
the mark position becomes invalid.reset()
public void reset() throws IOException
mark
method was last called on this input stream.
The
general contract of reset
is:
markSupported
returns true
, then: mark
has not been
called since the stream was created, or
the number of bytes read from the stream
since mark
was last called
is larger than the argument to mark
at that last call, then an IOException
might be thrown. IOException
is not thrown, then the stream is reset
to a state such that all the bytes read
since the most recent call to mark
(or since the start of the file, if mark
has not been called) will be resupplied
to subsequent callers of the read
method, followed by any bytes that otherwise
would have been the next input data as of
the time of the call to reset
.
markSupported
returns false
, then: reset
may throw an
IOException
. IOException
is not thrown, then the stream is reset
to a fixed state that depends on the particular
type of the input stream and how it was
created. The bytes that will be supplied
to subsequent callers of the read
method depend on the particular type of
the input stream.
The method
reset
for class InputStream
does nothing and always throws an IOException
.
mark(int)
,
IOException
public boolean markSupported()
mark
and reset
methods. The markSupported
method of InputStream
returns false
.true
if this true type supports the mark and reset
method; false
otherwise.mark(int)
,
reset()
|
Java Platform 1.2 Beta 4 |
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: INNER | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |