Closeable
, AutoCloseable
public class FileInputStream extends InputStream
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
.
close()
method should be called to release resources used by this stream, either directly, or with the try
-with-resources statement.Cleaner
or some other mechanism.Constructor | Description |
---|---|
FileInputStream |
Creates a FileInputStream by opening a connection to an actual file, the file named by the File object file in the file system. |
FileInputStream |
Creates a FileInputStream by using the file descriptor fdObj , which represents an existing connection to an actual file in the file system. |
FileInputStream |
Creates a FileInputStream by opening a connection to an actual file, the file named by the path name name in the file system. |
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. |
FileChannel |
getChannel() |
Returns the unique FileChannel object associated with this file input stream. |
final FileDescriptor |
getFD() |
Returns the FileDescriptor object that represents the connection to the actual file in the file system being used by this FileInputStream . |
int |
read() |
Reads a byte of data from this input stream. |
int |
read |
Reads up to b.length bytes of data from this input stream into an array of bytes. |
int |
read |
Reads up to len bytes of data from this input stream into an array of bytes. |
long |
skip |
Skips over and discards n bytes of data from the input stream. |
mark, markSupported, nullInputStream, readAllBytes, readNBytes, readNBytes, reset, skipNBytes, transferTo
public FileInputStream(String name) throws FileNotFoundException
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.
name
- the system-dependent file name.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.public FileInputStream(File file) throws FileNotFoundException
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.
file
- the file to be opened for reading.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.public FileInputStream(FileDescriptor fdObj)
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.
fdObj
- the file descriptor to be opened for reading.SecurityException
- if a security manager exists and its checkRead
method denies read access to the file descriptor.public int read() throws IOException
read
in class InputStream
-1
if the end of the file is reached.IOException
- if an I/O error occurs.public int read(byte[] b) throws IOException
b.length
bytes of data from this input stream into an array of bytes. This method blocks until some input is available.read
in class InputStream
b
- the buffer into which the data is read.-1
if there is no more data because the end of the file has been reached.IOException
- if an I/O error occurs.public int read(byte[] b, int off, int len) throws IOException
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.read
in class InputStream
b
- the buffer into which the data is read.off
- the start offset in array b
at which the data is written.len
- the maximum number of bytes to read.-1
if there is no more data because the end of the stream has been reached.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.public long skip(long n) throws IOException
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.
skip
in class InputStream
n
- the number of bytes to be skipped.IOException
- if n is negative, if the stream does not support seek, or if an I/O error occurs.public int available() throws IOException
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.
available
in class InputStream
IOException
- if this file input stream has been closed by calling close
or an I/O error occurs.public void close() throws IOException
If this stream has an associated channel then the channel is closed as well.
close
in interface AutoCloseable
close
in interface Closeable
close
in class InputStream
close()
to perform cleanup actions is reliable only when called directly or when called by try-with-resources.Cleaner
mechanism. If this stream has an associated channel then this method will close the channel, which in turn will close this stream. Subclasses that override this method should be prepared to handle possible reentrant invocation.
IOException
- if an I/O error occurs.public final FileDescriptor getFD() throws IOException
FileDescriptor
object that represents the connection to the actual file in the file system being used by this FileInputStream
.IOException
- if an I/O error occurs.public FileChannel getChannel()
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.
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/io/FileInputStream.html