java.io

Class FileInputStream

public class FileInputStream extends InputStream

This class is a stream that reads its bytes from a file.

Constructor Summary
	FileInputStream(String name) This method initializes a `FileInputStream` to read from the specified named file.
	FileInputStream(File file) This method initializes a `FileInputStream` to read from the specified `File` object.
	FileInputStream(FileDescriptor fdObj) This method initializes a `FileInputStream` to read from the specified `FileDescriptor` object.

Method Summary
int	available() This method returns the number of bytes that can be read from this stream before a read can block.
void	close() This method closes the stream.
protected void	finalize()
FileChannel	getChannel() This method creates a java.nio.channels.FileChannel.
FileDescriptor	getFD() This method returns a `FileDescriptor` object representing the underlying native file handle of the file this stream is reading from
int	read() This method reads an unsigned byte from the input stream and returns it as an int in the range of 0-255.
int	read(byte[] buf) This method reads bytes from a stream and stores them into a caller supplied buffer.
int	read(byte[] buf, int offset, int len) This method read bytes from a stream and stores them into a caller supplied buffer.
long	skip(long numBytes) This method skips the specified number of bytes in the stream.

This method initializes a FileInputStream to read from the specified named file. A security check is first made to determine whether or not access to this file is allowed. This is done by calling the checkRead() method of the SecurityManager (if one exists) with the name of this file. An exception is thrown if reading is not allowed. If the file does not exist, an exception is also thrown.

Parameters: name The name of the file this stream should read from

Throws: SecurityException If read access to the file is not allowed FileNotFoundException If the file does not exist or if it is a directory

FileInputStream

public FileInputStream(File file)

This method initializes a FileInputStream to read from the specified File object. A security check is first made to determine whether or not access to this file is allowed. This is done by calling the checkRead() method of the SecurityManager (if one exists) with the name of this file. An exception is thrown if reading is not allowed. If the file does not exist, an exception is also thrown.

Parameters: file The File object this stream should read from

Throws: SecurityException If read access to the file is not allowed FileNotFoundException If the file does not exist or if it is a directory.

FileInputStream

public FileInputStream(FileDescriptor fdObj)

This method initializes a FileInputStream to read from the specified FileDescriptor object. A security check is first made to determine whether or not access to this file is allowed. This is done by calling the checkRead() method of the SecurityManager (if one exists) with the specified FileDescriptor An exception is thrown if reading is not allowed.

Parameters: fdObj The FileDescriptor object this stream should read from

Throws: SecurityException If read access to the file is not allowed

Method Detail

available

public int available()

This method returns the number of bytes that can be read from this stream before a read can block. A return of 0 indicates that blocking might (or might not) occur on the very next read attempt.

This method returns the number of unread bytes remaining in the file if the descriptor being read from is an actual file. If this method is reading from a ''special'' file such a the standard input, this method will return the appropriate value for the stream being read.

Be aware that reads on plain files that do not reside locally might possibly block even if this method says they should not. For example, a remote server might crash, preventing an NFS mounted file from being read.

Returns: The number of bytes that can be read before blocking could occur

Throws: IOException If an error occurs

close

public void close()

This method closes the stream. Any futher attempts to read from the stream will likely generate an IOException since the underlying file will be closed.

Throws: IOException If an error occurs.

finalize

protected void finalize()

getChannel

public FileChannel getChannel()

This method creates a java.nio.channels.FileChannel. Nio does not allow one to create a file channel directly. A file channel must be created by first creating an instance of Input/Output/RandomAccessFile and invoking the getChannel() method on it.

getFD

public final FileDescriptor getFD()

This method returns a FileDescriptor object representing the underlying native file handle of the file this stream is reading from

Returns: A FileDescriptor for this stream

Throws: IOException If an error occurs

read

public int read()

This method reads an unsigned byte from the input stream and returns it as an int in the range of 0-255. This method also will return -1 if the end of the stream has been reached.

This method will block until the byte can be read.

Returns: The byte read or -1 if end of stream

Throws: IOException If an error occurs

read

public int read(byte[] buf)

This method reads bytes from a stream and stores them into a caller supplied buffer. This method attempts to completely fill the buffer, but can return before doing so. The actual number of bytes read is returned as an int. A -1 is returned to indicate the end of the stream.

This method will block until some data can be read.

This method operates by calling an overloaded read method like so: read(buf, 0, buf.length)

Parameters: buf The buffer into which the bytes read will be stored.

Returns: The number of bytes read or -1 if end of stream.

Throws: IOException If an error occurs.

read

public int read(byte[] buf, int offset, int len)

This method read bytes from a stream and stores them into a caller supplied buffer. It starts storing the data at index offset into the buffer and attempts to read len bytes. This method can return before reading the number of bytes requested. The actual number of bytes read is returned as an int. A -1 is returned to indicate the end of the stream.

This method will block until some data can be read.

Parameters: buf The array into which the bytes read should be stored offset The offset into the array to start storing bytes len The requested number of bytes to read

Returns: The actual number of bytes read, or -1 if end of stream.

Throws: IOException If an error occurs.

skip

public long skip(long numBytes)

This method skips the specified number of bytes in the stream. It returns the actual number of bytes skipped, which may be less than the requested amount.

Parameters: numBytes The requested number of bytes to skip

Returns: The actual number of bytes skipped.

Throws: IOException If an error occurs