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.
File,
FileDescriptor,
FileOutputStream,
Files.newInputStream(java.nio.file.Path, java.nio.file.OpenOption...)
| Constructor and Description |
|---|
FileInputStream(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
Creates a
FileInputStream by using the file descriptor
fdObj, which represents an existing connection to an actual file in the file system.
|
FileInputStream(String
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.
|
protected void |
finalize()
Ensures that the
close method of this file input stream is called when there are no more references to it.
|
FileChannel |
getChannel()
Returns the unique
FileChannel object associated with this file input stream.
|
java |
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(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.
|
mark, markSupported, resetpublic FileInputStream(Stringname) 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.
SecurityManager.checkRead(java.lang.String)
public FileInputStream(Filefile) 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.
File.getPath() ,
SecurityManager.checkRead(java.lang.String)
public FileInputStream(java.io .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.
SecurityManager.checkRead(java.io.FileDescriptor)
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.
InputStream.read(byte[], int, int)
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 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.
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.
InputStream.read()
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
Closeable
close in interface
AutoCloseable
close in class
InputStream
IOException - if an I/O error occurs.
public final java.io .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.
FileDescriptor
public FileChannelgetChannel()
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.
protected void finalize()
throws IOException
close method of this file input stream is called when there are no more references to it.
finalize in class
Object
IOException - if an I/O error occurs.
close()