java.io
Class FileInputStream

java.lang.Object
  java.io.InputStream
      java.io.FileInputStream

public class FileInputStream
extends InputStream

FileInputStream is a class for reading bytes from a file. This class may also be used with other InputStreams, ie: BufferedInputStream, to read data from a file with buffering.

See Also:

FileOutputStream

Constructor Summary

FileInputStream(File file)
Constructs a new FileInputStream on the File file.

FileInputStream(FileDescriptor fd)
Constructs a new FileInputStream on the FileDescriptor fd.

FileInputStream(String fileName)
Constructs a new FileInputStream on the file named fileName.

Method Summary

int	available() Answers a int representing then number of bytes that are available before this InputStream will block.
void	close() Close the FileInputStream.
protected void	finalize() This method ensures that all resources for this file are released when it is about to be garbage collected.
FileChannel	getChannel() Answers the FileChannel equivalent to this input stream.
FileDescriptor	getFD() Answers the FileDescriptor representing the operating system resource for this FileInputStream.
int	read() Reads a single byte from this FileInputStream and returns the result as an int.
int	read(byte[] buffer) Reads bytes from the FileInputStream and stores them in byte array buffer.
int	read(byte[] buffer, int offset, int count) Reads at most count bytes from the FileInputStream and stores them in byte array buffer starting at offset.
long	skip(long count) Skips count number of bytes in this FileInputStream.

Methods inherited from class java.io.InputStream

mark, markSupported, reset

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FileInputStream

public FileInputStream(File file)
                throws FileNotFoundException

Constructs a new FileInputStream on the File file. If the file does not exist, the FileNotFoundException is thrown.

Parameters:

file - the File on which to stream reads.

Throws:

FileNotFoundException - If the file is not found.

See Also:

SecurityManager.checkRead(FileDescriptor), SecurityManager.checkRead(String), SecurityManager.checkRead(String, Object)

FileInputStream

public FileInputStream(FileDescriptor fd)

Constructs a new FileInputStream on the FileDescriptor fd. The file must already be open, therefore no FileNotFoundException will be thrown.

Parameters:

fd - the FileDescriptor on which to stream reads.

See Also:

SecurityManager.checkRead(FileDescriptor), SecurityManager.checkRead(String), SecurityManager.checkRead(String, Object)

FileInputStream

public FileInputStream(String fileName)
                throws FileNotFoundException

Constructs a new FileInputStream on the file named fileName. If the file does not exist, the FileNotFoundException is thrown. The fileName may be absolute or relative to the System property "user.dir".

Parameters:

fileName - the file on which to stream reads.

Throws:

FileNotFoundException - If the fileName is not found.

Method Detail

available

public int available()
              throws IOException

Answers a int representing then number of bytes that are available before this InputStream will block. This method always returns the size of the file minus the current position.

Overrides:

available in class InputStream

Returns:

the number of bytes available before blocking.

Throws:

IOException - If an error occurs in this stream.

close

public void close()
           throws IOException

Close the FileInputStream.

Overrides:

close in class InputStream

Throws:

IOException - If an error occurs attempting to close this FileInputStream.

finalize

protected void finalize()
                 throws IOException

This method ensures that all resources for this file are released when it is about to be garbage collected.

Overrides:

finalize in class Object

Throws:

IOException - If an error occurs attempting to finalize this FileInputStream.

getChannel

public FileChannel getChannel()

Answers the FileChannel equivalent to this input stream.

The file channel is read-only and has an initial position within the file that is the same as the current position of the FileInputStream within the file. All changes made to the underlying file descriptor state via the channel are visible by the input stream and vice versa.

Returns:

the file channel representation for this FileInputStream.

getFD

public final FileDescriptor getFD()
                           throws IOException

Answers the FileDescriptor representing the operating system resource for this FileInputStream.

Returns:

the FileDescriptor for this FileInputStream.

Throws:

IOException - If an error occurs attempting to get the FileDescriptor of this FileInputStream.

read

public int read()
         throws IOException

Reads a single byte from this FileInputStream and returns the result as an int. The low-order byte is returned or -1 of the end of stream was encountered.

Specified by:

read in class InputStream

Returns:

the byte read or -1 if end of stream.

Throws:

IOException - If the stream is already closed or another IOException occurs.

read

public int read(byte[] buffer)
         throws IOException

Reads bytes from the FileInputStream and stores them in byte array buffer. Answer the number of bytes actually read or -1 if no bytes were read and end of stream was encountered.

Overrides:

read in class InputStream

Parameters:

buffer - the byte array in which to store the read bytes.

Returns:

the number of bytes actually read or -1 if end of stream.

Throws:

IOException - If the stream is already closed or another IOException occurs.

read

public int read(byte[] buffer,
                int offset,
                int count)
         throws IOException

Reads at most count bytes from the FileInputStream and stores them in byte array buffer starting at offset. Answer the number of bytes actually read or -1 if no bytes were read and end of stream was encountered.

Overrides:

read in class InputStream

Parameters:

buffer - the byte array in which to store the read bytes.

offset - the offset in buffer to store the read bytes.

count - the maximum number of bytes to store in buffer.

Returns:

the number of bytes actually read or -1 if end of stream.

Throws:

IOException - If the stream is already closed or another IOException occurs.

skip

public long skip(long count)
          throws IOException

Skips count number of bytes in this FileInputStream. Subsequent read()'s will not return these bytes unless reset() is used. This method may perform multiple reads to read count bytes. This default implementation reads count bytes into a temporary buffer.

Overrides:

skip in class InputStream

Parameters:

count - the number of bytes to skip.

Returns:

the number of bytes actually skipped.

Throws:

IOException - If the stream is already closed or another IOException occurs.