Class FileInputStream
- java.lang.Object
-
- java.io.InputStream
-
- java.io.FileInputStream
- All Implemented Interfaces:
-
Closeable
,AutoCloseable
public class FileInputStream extends InputStream
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
.
- API Note:
- To release resources used by this stream
close()
should be called directly or by try-with-resources. Subclasses are responsible for the cleanup of resources acquired by the subclass. Subclasses that overridefinalize()
in order to perform cleanup should be modified to use alternative cleanup mechanisms such asCleaner
and remove the overridingfinalize
method. - Implementation Requirements:
- If this FileInputStream has been subclassed and the
close()
method has been overridden, theclose()
method will be called when the FileInputStream is unreachable. Otherwise, it is implementation specific how the resource cleanup described inclose()
is performed. - Since:
- 1.0
- See Also:
-
File
,FileDescriptor
,FileOutputStream
,Files.newInputStream(java.nio.file.Path, java.nio.file.OpenOption...)
Constructor Summary
Constructor | Description |
---|---|
FileInputStream(File file) | Creates a |
FileInputStream(FileDescriptor fdObj) | Creates a |
FileInputStream(String name) | Creates a |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
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. |
protected void | finalize() | Deprecated, for removal: This API element is subject to removal in a future version. The finalize method has been deprecated and will be removed. |
FileChannel | getChannel() | Returns the unique |
FileDescriptor | getFD() | Returns the |
int | read() | Reads a 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 |
long | skip(long n) | Skips over and discards |
Methods declared in class java.io.InputStream
mark, markSupported, nullInputStream, readAllBytes, readNBytes, readNBytes, reset, transferTo
Methods declared in class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Constructor Detail
FileInputStream
public FileInputStream(String name) throws FileNotFoundException
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
- 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 itscheckRead
method denies read access to the file. - See Also:
SecurityManager.checkRead(java.lang.String)
FileInputStream
public FileInputStream(File file) throws FileNotFoundException
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
- 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 itscheckRead
method denies read access to the file. - See Also:
-
File.getPath()
,SecurityManager.checkRead(java.lang.String)
FileInputStream
public 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
- the file descriptor to be opened for reading. - Throws:
-
SecurityException
- if a security manager exists and itscheckRead
method denies read access to the file descriptor. - See Also:
SecurityManager.checkRead(java.io.FileDescriptor)
Method Detail
read
public int read() throws IOException
Reads a byte of data from this input stream. This method blocks if no input is yet available.
- Specified by:
-
read
in classInputStream
- Returns:
- the next byte of data, or
-1
if the end of the file is reached. - Throws:
-
IOException
- if an I/O error occurs.
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.
- 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 file has been reached. - Throws:
-
IOException
- if an I/O error occurs. - See Also:
InputStream.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.
- 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 file 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:
InputStream.read()
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
. If n
is negative, the method will try to skip backwards. In case the backing file does not support backward skip at its current position, an IOException
is thrown. The actual number of bytes skipped is returned. If it skips forwards, it returns a positive value. If it skips backwards, it returns a negative value.
This method may skip more bytes than what 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.
- Overrides:
-
skip
in classInputStream
- Parameters:
-
n
- the number of bytes to be skipped. - Returns:
- 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.
available
public int available() throws IOException
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. Returns 0 when the file position is beyond EOF. 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.
- Overrides:
-
available
in classInputStream
- Returns:
- 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 callingclose
or an I/O error occurs.
close
public void close() throws IOException
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.
- Specified by:
-
close
in interfaceAutoCloseable
- Specified by:
-
close
in interfaceCloseable
- Overrides:
-
close
in classInputStream
- API Note:
- Overriding
close()
to perform cleanup actions is reliable only when called directly or when called by try-with-resources. Do not depend on finalization to invokeclose
; finalization is not reliable and is deprecated. If cleanup of native resources is needed, other mechanisms such as Cleaner should be used. - Throws:
-
IOException
- if an I/O error occurs.
getFD
public final FileDescriptor getFD() throws IOException
Returns the FileDescriptor
object that represents the connection to the actual file in the file system being used by this FileInputStream
.
- Returns:
- the file descriptor object associated with this stream.
- Throws:
-
IOException
- if an I/O error occurs. - See Also:
FileDescriptor
getChannel
public 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:
- the file channel associated with this file input stream
- Since:
- 1.4
finalize
@Deprecated(since="9", forRemoval=true) protected void finalize() throws IOException
finalize
method has been deprecated and will be removed. Subclasses that override finalize
in order to perform cleanup should be modified to use alternative cleanup mechanisms and to remove the overriding finalize
method. When overriding the finalize
method, its implementation must explicitly ensure that super.finalize()
is invoked as described in Object.finalize()
. See the specification for Object.finalize()
for further information about migration options.Ensures that the close()
method of this file input stream is called when there are no more references to it. The finalize()
method does not call close()
directly.
- Overrides:
-
finalize
in classObject
- API Note:
- To release resources used by this stream
close()
should be called directly or by try-with-resources. - Implementation Requirements:
- If this FileInputStream has been subclassed and the
close()
method has been overridden, theclose()
method will be called when the FileInputStream is unreachable. Otherwise, it is implementation specific how the resource cleanup described inclose()
is performed. - Throws:
-
IOException
- if an I/O error occurs. - See Also:
close()