public class FileInputStream
extends java.io.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
.
File
,
FileOutputStream
Constructor and Description |
---|
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. |
FileInputStream(java.lang.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. |
Modifier and Type | Method and 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.
|
int |
read()
Reads a byte of data from this input stream.
|
int |
read(byte[] b)
Reads up to
b.length bytes of data from this input
stream into an array of bytes. |
int |
read(byte[] b,
int off,
int len)
Reads up to
len bytes of data from this input stream
into an array of bytes. |
long |
skip(long n)
Skips over and discards
n bytes of data from the
input stream. |
public FileInputStream(java.lang.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.
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.java.lang.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.
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.java.lang.SecurityException
- if a security manager exists and its
checkRead
method denies read access to the file.File.getPath()
public int read() throws java.io.IOException
read
in class java.io.InputStream
-1
if the end of the
file is reached.IOException
- if an I/O error occurs.public int read(byte[] b) throws java.io.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 java.io.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 java.io.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 java.io.InputStream
b
- the buffer into which the data is read.off
- the start offset in the destination array b
len
- the maximum number of bytes read.-1
if there is no more data because the end of
the file has been reached.java.lang.NullPointerException
- If b
is null
.java.lang.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 java.io.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 java.io.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 java.io.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 java.io.InputStream
IOException
- if this file input stream has been closed by calling
close
or an I/O error occurs.public void close() throws java.io.IOException
If this stream has an associated channel then the channel is closed as well.
close
in interface java.io.Closeable
close
in interface java.lang.AutoCloseable
close
in class java.io.InputStream
IOException
- if an I/O error occurs.