FileInputStream

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public class FileInputStream extends InputStream

A 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.

Public Constructor Summary

FileInputStream(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.
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(FileDescriptor fdObj)
Creates a FileInputStream by using the file descriptor fdObj, which represents an existing connection to an actual file in the file system.

Public Method Summary

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(byte[] b, int off, int len)
Reads up to len bytes of data from this input stream into an array of bytes.
int
read(byte[] b)
Reads up to b.length bytes of data from this input stream into an array of bytes.
long
skip(long byteCount)
Skips over and discards n bytes of data from the input stream.

Protected Method Summary

void
finalize()
Ensures that the close method of this file input stream is called when there are no more references to it.

Inherited Method Summary

Public Constructors

public FileInputStream (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. 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.

Parameters
name the system-dependent file name.
Throws
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)

Creates a 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.

Parameters
file the file to be opened for reading.
Throws
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)

Creates a 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.

Parameters
fdObj the file descriptor to be opened for reading.

Public Methods

public 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. Returns 0 when the file position is beyond EOF. The next invocation might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.

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.

Returns
  • an estimate of the number of remaining bytes that can be read (or skipped over) from this input stream without blocking.
Throws
IOException if this file input stream has been closed by calling close or an I/O error occurs.

public void close ()

Closes this file input stream and releases any system resources associated with the stream.

If this stream has an associated channel then the channel is closed as well.

Throws
IOException if an I/O error occurs.

public FileChannel getChannel ()

Returns the unique 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.

Returns
  • the file channel associated with this file input stream

public final FileDescriptor getFD ()

Returns the FileDescriptor object that represents the connection to the actual file in the file system being used by this FileInputStream.

Returns
  • the file descriptor object associated with this stream.
Throws
IOException if an I/O error occurs.
See Also

public int read ()

Reads a byte of data from this input stream. This method blocks if no input is yet available.

Returns
  • the next byte of data, or -1 if the end of the file is reached.
Throws
IOException if an I/O error occurs.

public int read (byte[] b, int off, int len)

Reads up to 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.

Parameters
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.
Returns
  • the total number of bytes read into the buffer, or -1 if there is no more data because the end of the file has been reached.
Throws
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 int read (byte[] b)

Reads up to b.length bytes of data from this input stream into an array of bytes. This method blocks until some input is available.

Parameters
b the buffer into which the data is read.
Returns
  • the total number of bytes read into the buffer, or -1 if there is no more data because the end of the file has been reached.
Throws
IOException if an I/O error occurs.

public long skip (long byteCount)

Skips over and discards 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.

Parameters
byteCount the number of bytes to be skipped.
Returns
  • the actual number of bytes skipped.
Throws
IOException if n is negative, if the stream does not support seek, or if an I/O error occurs.

Protected Methods

protected void finalize ()

Ensures that the close method of this file input stream is called when there are no more references to it.

Throws
IOException if an I/O error occurs.
See Also