FileInputStream (Java Platform SE 6) (original) (raw)

java.io

Class FileInputStream

java.lang.Object extended by java.io.InputStream java.io.FileInputStream

All Implemented Interfaces:

public class FileInputStream

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 usingFileReader.

Since:

JDK1.0

See Also:

File, FileDescriptor, FileOutputStream

Constructor Summary
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 descriptorfdObj, which represents an existing connection to an actual file in the file system.
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.

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.
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.
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) Reads up to b.length bytes of data from this input stream into an array of bytes.
int	[read](../../java/io/FileInputStream.html#read%28byte[], int, int%29)(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.

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](../../java/lang/Object.html#wait%28long, int%29)

Constructor Detail

FileInputStream

public FileInputStream(String name) throws FileNotFoundException

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 aFileNotFoundException is thrown.

Parameters:

name - the system-dependent file name.

Throws:

[FileNotFoundException](../../java/io/FileNotFoundException.html "class in java.io") - 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](../../java/lang/SecurityException.html "class in java.lang") - if a security manager exists and itscheckRead method denies read access to the file.

FileInputStream

public FileInputStream(File file) throws FileNotFoundException

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 aFileNotFoundException is thrown.

Parameters:

file - the file to be opened for reading.

Throws:

[SecurityException](../../java/lang/SecurityException.html "class in java.lang") - if a security manager exists and itscheckRead method denies read access to the file.

FileInputStream

public FileInputStream(FileDescriptor fdObj)

Creates a FileInputStream by using the file descriptorfdObj, 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.

Parameters:

fdObj - the file descriptor to be opened for reading.

Throws:

[SecurityException](../../java/lang/SecurityException.html "class in java.lang") - if a security manager exists and itscheckRead method denies read access to the file descriptor.

Method Detail

read

public int read() throws IOException

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

Specified by:

[read](../../java/io/InputStream.html#read%28%29) in class [InputStream](../../java/io/InputStream.html "class in java.io")

Returns:

the next byte of data, or -1 if the end of the file is reached.

Throws:

[IOException](../../java/io/IOException.html "class in java.io") - if an I/O error occurs.

read

public int read(byte[] b) throws IOException

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.

Overrides:

[read](../../java/io/InputStream.html#read%28byte[]%29) in class [InputStream](../../java/io/InputStream.html "class in java.io")

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](../../java/io/IOException.html "class in java.io") - if an I/O error occurs.

See Also:

[InputStream.read(byte[], int, int)](../../java/io/InputStream.html#read%28byte[], int, int%29)

read

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

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.

Overrides:

[read](../../java/io/InputStream.html#read%28byte[], int, int%29) in class [InputStream](../../java/io/InputStream.html "class in java.io")

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](../../java/lang/NullPointerException.html "class in java.lang") - If b is null.

[IndexOutOfBoundsException](../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - If off is negative, len is negative, or len is greater than b.length - off

[IOException](../../java/io/IOException.html "class in java.io") - if an I/O error occurs.

See Also:

InputStream.read()

skip

public long skip(long n) throws IOException

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, anIOException is thrown, even though the skip method of the InputStream superclass does nothing in this case. The actual number of bytes skipped is returned.

This method may skip more bytes than 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.

Overrides:

[skip](../../java/io/InputStream.html#skip%28long%29) in class [InputStream](../../java/io/InputStream.html "class in java.io")

Parameters:

n - the number of bytes to be skipped.

Returns:

the actual number of bytes skipped.

Throws:

[IOException](../../java/io/IOException.html "class in java.io") - if n is negative, if the stream does not support seek, or if an I/O error occurs.

available

public int available() throws IOException

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. 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.

Overrides:

[available](../../java/io/InputStream.html#available%28%29) in class [InputStream](../../java/io/InputStream.html "class in java.io")

Returns:

an estimate of the number of remaining bytes that can be read (or skipped over) from this input stream without blocking.

Throws:

[IOException](../../java/io/IOException.html "class in java.io") - if this file input stream has been closed by callingclose or an I/O error occurs.

close

public void close() throws IOException

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.

Specified by:

[close](../../java/io/Closeable.html#close%28%29) in interface [Closeable](../../java/io/Closeable.html "interface in java.io")

Overrides:

[close](../../java/io/InputStream.html#close%28%29) in class [InputStream](../../java/io/InputStream.html "class in java.io")

Throws:

[IOException](../../java/io/IOException.html "class in java.io") - if an I/O error occurs.

getFD

public final FileDescriptor getFD() throws IOException

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](../../java/io/IOException.html "class in java.io") - if an I/O error occurs.

See Also:

FileDescriptor

getChannel

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

Since:

1.4

finalize

protected void finalize() throws IOException

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

Overrides:

[finalize](../../java/lang/Object.html#finalize%28%29) in class [Object](../../java/lang/Object.html "class in java.lang")

Throws:

[IOException](../../java/io/IOException.html "class in java.io") - if an I/O error occurs.

See Also:

close()

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