public
class
FileInputStream
extends InputStream
java.lang.Object | ||
↳ | java.io.InputStream | |
↳ | java.io.FileInputStream |
Known Direct Subclasses |
Known Indirect Subclasses |
A FileInputStream
obtains input bytes
from a file in a file system. What files
are available depends on the host environment.
FileInputStream
is meant for reading streams of raw bytes
such as image data. For reading streams of characters, consider using
FileReader
.
Public constructors | |
---|---|
FileInputStream(String name)
Creates a |
|
FileInputStream(File file)
Creates a |
|
FileInputStream(FileDescriptor fdObj)
Creates a |
Public methods | |
---|---|
int
|
available()
Returns an estimate of the number of remaining bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. |
void
|
close()
Closes this file input stream and releases any system resources associated with the stream. |
FileChannel
|
getChannel()
Returns the unique |
final
FileDescriptor
|
getFD()
Returns the |
int
|
read()
Reads a byte of data from this input stream. |
int
|
read(byte[] b, int off, int len)
Reads up to |
int
|
read(byte[] b)
Reads up to |
long
|
skip(long n)
Skips over and discards |
Protected methods | |
---|---|
void
|
finalize()
Ensures that the |
Inherited methods | |
---|---|
From
class
java.io.InputStream
| |
From
class
java.lang.Object
| |
From
interface
java.io.Closeable
| |
From
interface
java.lang.AutoCloseable
|
FileInputStream (String name)
Creates a FileInputStream
by
opening a connection to an actual file,
the file named by the path name name
in the file system. A new FileDescriptor
object is created to represent this file
connection.
First, if there is a security
manager, its checkRead
method
is called with the name
argument
as its argument.
If the named file does not exist, is a directory rather than a regular
file, or for some other reason cannot be opened for reading then a
FileNotFoundException
is thrown.
Parameters | |
---|---|
name |
String :
the system-dependent file name. |
Throws | |
---|---|
FileNotFoundException |
if the file does not exist, is a directory rather than a regular file, or for some other reason cannot be opened for reading. |
SecurityException |
if a security manager exists and its
checkRead method denies read access
to the file. |
See also:
FileInputStream (File file)
Creates a FileInputStream
by
opening a connection to an actual file,
the file named by the File
object file
in the file system.
A new FileDescriptor
object
is created to represent this file connection.
First, if there is a security manager,
its checkRead
method is called
with the path represented by the file
argument as its argument.
If the named file does not exist, is a directory rather than a regular
file, or for some other reason cannot be opened for reading then a
FileNotFoundException
is thrown.
Parameters | |
---|---|
file |
File :
the file to be opened for reading. |
Throws | |
---|---|
FileNotFoundException |
if the file does not exist, is a directory rather than a regular file, or for some other reason cannot be opened for reading. |
SecurityException |
if a security manager exists and its
checkRead method denies read access to the file. |
See also:
FileInputStream (FileDescriptor fdObj)
Creates a FileInputStream
by using the file descriptor
fdObj
, which represents an existing connection to an
actual file in the file system.
If there is a security manager, its checkRead
method is
called with the file descriptor fdObj
as its argument to
see if it's ok to read the file descriptor. If read access is denied
to the file descriptor a SecurityException
is thrown.
If fdObj
is null then a NullPointerException
is thrown.
This constructor does not throw an exception if fdObj
is invalid
.
However, if the methods are invoked on the resulting stream to attempt
I/O on the stream, an IOException
is thrown.
Parameters | |
---|---|
fdObj |
FileDescriptor :
the file descriptor to be opened for reading.
|
int available ()
Returns an estimate of the number of remaining bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. The next invocation 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.
In some cases, a non-blocking read (or skip) may appear to be blocked when it is merely slow, for example when reading large files over slow networks.
Returns | |
---|---|
int |
an estimate of the number of remaining bytes that can be read (or skipped over) from this input stream without blocking. |
Throws | |
---|---|
IOException |
if this file input stream has been closed by calling
close or an I/O error occurs.
|
void close ()
Closes this file input stream and releases any system resources associated with the stream.
If this stream has an associated channel then the channel is closed as well.
Throws | |
---|---|
IOException |
if an I/O error occurs. |
FileChannel getChannel ()
Returns the unique FileChannel
object associated with this file input stream.
The initial position
of the returned channel will be equal to the
number of bytes read from the file so far. Reading bytes from this
stream will increment the channel's position. Changing the channel's
position, either explicitly or by reading, will change this stream's
file position.
Returns | |
---|---|
FileChannel |
the file channel associated with this file input stream |
FileDescriptor getFD ()
Returns the FileDescriptor
object that represents the connection to
the actual file in the file system being
used by this FileInputStream
.
Returns | |
---|---|
FileDescriptor |
the file descriptor object associated with this stream. |
Throws | |
---|---|
IOException |
if an I/O error occurs. |
See also:
int read ()
Reads a byte of data from this input stream. This method blocks if no input is yet available.
Returns | |
---|---|
int |
the next byte of data, or -1 if the end of the
file is reached. |
Throws | |
---|---|
IOException |
if an I/O error occurs. |
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.
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 file 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. |
int read (byte[] b)
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.
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 file has been reached. |
Throws | |
---|---|
IOException |
if an I/O error occurs. |
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
. If n
is negative, an
IOException
is thrown, even though the skip
method of the InputStream
superclass does nothing in this case.
The actual number of bytes skipped is returned.
This method may skip more bytes than are remaining in the backing file. This produces no exception and the number of bytes skipped may include some number of bytes that were beyond the EOF of the backing file. Attempting to read from the stream after skipping past the end will result in -1 indicating the end of the file.
Parameters | |
---|---|
n |
long :
the number of bytes to be skipped. |
Returns | |
---|---|
long |
the actual number of bytes skipped. |
Throws | |
---|---|
IOException |
if n is negative, if the stream does not support seek, or if an I/O error occurs. |
void finalize ()
Ensures that the close
method of this file input stream is
called when there are no more references to it.
Throws | |
---|---|
IOException |
if an I/O error occurs. |
See also: