Module java.base

Package java.io

Class FileOutputStream

java.lang.Object

java.io.OutputStream

java.io.FileOutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

public class FileOutputStream
extends OutputStream

A file output stream is an output stream for writing data to a File or to a FileDescriptor. Whether or not a file is available or may be created depends upon the underlying platform. Some platforms, in particular, allow a file to be opened for writing by only one FileOutputStream (or other file-writing object) at a time. In such situations the constructors in this class will fail if the file involved is already open.

FileOutputStream is meant for writing streams of raw bytes such as image data. For writing streams of characters, consider using FileWriter.

API Note:

The close() method should be called to release resources used by this stream, either directly, or with the try-with-resources statement.

Implementation Requirements:

Subclasses are responsible for the cleanup of resources acquired by the subclass. Subclasses requiring that resource cleanup take place after a stream becomes unreachable should use Cleaner or some other mechanism.

Since:

1.0

See Also:

• File
• FileDescriptor
• FileInputStream
• Files.newOutputStream(java.nio.file.Path, java.nio.file.OpenOption...)

Constructor Summary

Constructors

Constructor	Description
FileOutputStream(File file)	Creates a file output stream to write to the file represented by the specified File object.
FileOutputStream(FileDescriptor fdObj)	Creates a file output stream to write to the specified file descriptor, which represents an existing connection to an actual file in the file system.
FileOutputStream(File file, boolean append)	Creates a file output stream to write to the file represented by the specified File object.
FileOutputStream(String name)	Creates a file output stream to write to the file with the specified name.
FileOutputStream(String name, boolean append)	Creates a file output stream to write to the file with the specified name.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes this file output stream and releases any system resources associated with this stream.
FileChannel	getChannel()	Returns the unique FileChannel object associated with this file output stream.
final FileDescriptor	getFD()	Returns the file descriptor associated with this stream.
void	write(byte[] b)	Writes b.length bytes from the specified byte array to this file output stream.
void	write(byte[] b, int off, int len)	Writes len bytes from the specified byte array starting at offset off to this file output stream.
void	write(int b)	Writes the specified byte to this file output stream.

Methods declared in class java.io.OutputStream

flush, nullOutputStream

Methods declared in class java.lang.Object

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

Constructor Details

FileOutputStream

public FileOutputStream(String name)
                 throws FileNotFoundException

Creates a file output stream to write to the file with the specified name. A new FileDescriptor object is created to represent this file connection.

First, if there is a security manager, its checkWrite method is called with name as its argument.

If the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason then a FileNotFoundException is thrown.

Implementation Requirements:

Invoking this constructor with the parameter name is equivalent to invoking new FileOutputStream(name, false).

Parameters:

name - the system-dependent filename

Throws:

FileNotFoundException - if the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason

SecurityException - if a security manager exists and its checkWrite method denies write access to the file.

See Also:

• SecurityManager.checkWrite(java.lang.String)

FileOutputStream

public FileOutputStream(String name,
 boolean append)
                 throws FileNotFoundException

Creates a file output stream to write to the file with the specified name. If the second argument is true, then bytes will be written to the end of the file rather than the beginning. A new FileDescriptor object is created to represent this file connection.

First, if there is a security manager, its checkWrite method is called with name as its argument.

If the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason then a FileNotFoundException is thrown.

Parameters:

name - the system-dependent file name

append - if true, then bytes will be written to the end of the file rather than the beginning

Throws:

FileNotFoundException - if the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason.

SecurityException - if a security manager exists and its checkWrite method denies write access to the file.

Since:

1.1

See Also:

• SecurityManager.checkWrite(java.lang.String)

FileOutputStream

public FileOutputStream(File file)
                 throws FileNotFoundException

Creates a file output stream to write to the file represented by the specified File object. A new FileDescriptor object is created to represent this file connection.

First, if there is a security manager, its checkWrite method is called with the path represented by the file argument as its argument.

If the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason then a FileNotFoundException is thrown.

Parameters:

file - the file to be opened for writing.

Throws:

FileNotFoundException - if the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason

SecurityException - if a security manager exists and its checkWrite method denies write access to the file.

See Also:

• File.getPath()
• SecurityException
• SecurityManager.checkWrite(java.lang.String)

FileOutputStream

public FileOutputStream(File file,
 boolean append)
                 throws FileNotFoundException

Creates a file output stream to write to the file represented by the specified File object. If the second argument is true, then bytes will be written to the end of the file rather than the beginning. A new FileDescriptor object is created to represent this file connection.

First, if there is a security manager, its checkWrite method is called with the path represented by the file argument as its argument.

If the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason then a FileNotFoundException is thrown.

Parameters:

file - the file to be opened for writing.

append - if true, then bytes will be written to the end of the file rather than the beginning

Throws:

FileNotFoundException - if the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason

SecurityException - if a security manager exists and its checkWrite method denies write access to the file.

Since:

1.4

See Also:

• File.getPath()
• SecurityException
• SecurityManager.checkWrite(java.lang.String)

FileOutputStream

public FileOutputStream(FileDescriptor fdObj)

Creates a file output stream to write to the specified file descriptor, which represents an existing connection to an actual file in the file system.

First, if there is a security manager, its checkWrite method is called with the file descriptor fdObj argument as its argument.

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 writing

Throws:

SecurityException - if a security manager exists and its checkWrite method denies write access to the file descriptor

See Also:

• SecurityManager.checkWrite(java.io.FileDescriptor)

Method Details

write

public void write(int b)
           throws IOException

Writes the specified byte to this file output stream. Implements the write method of OutputStream.

Specified by:

write in class OutputStream

Parameters:

b - the byte to be written.

Throws:

IOException - if an I/O error occurs.

write

public void write(byte[] b)
           throws IOException

Writes b.length bytes from the specified byte array to this file output stream.

Overrides:

write in class OutputStream

Parameters:

b - the data.

Throws:

IOException - if an I/O error occurs.

See Also:

• OutputStream.write(byte[], int, int)

write

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

Writes len bytes from the specified byte array starting at offset off to this file output stream.

Overrides:

write in class OutputStream

Parameters:

b - the data.

off - the start offset in the data.

len - the number of bytes to write.

Throws:

IOException - if an I/O error occurs.

IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off

close

public void close()
           throws IOException

Closes this file output stream and releases any system resources associated with this stream. This file output stream may no longer be used for writing bytes.

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

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class OutputStream

API Note:

Overriding close() to perform cleanup actions is reliable only when called directly or when called by try-with-resources.

Implementation Requirements:

Subclasses requiring that resource cleanup take place after a stream becomes unreachable should use the Cleaner mechanism.

If this stream has an associated channel then this method will close the channel, which in turn will close this stream. Subclasses that override this method should be prepared to handle possible reentrant invocation.

Throws:

IOException - if an I/O error occurs.

getFD

public final FileDescriptor getFD()
                           throws IOException

Returns the file descriptor associated with this stream.

Returns:

the FileDescriptor object that represents the connection to the file in the file system being used by this FileOutputStream object.

Throws:

IOException - if an I/O error occurs.

See Also:

• FileDescriptor

getChannel

public FileChannel getChannel()

Returns the unique FileChannel object associated with this file output stream.

The initial position of the returned channel will be equal to the number of bytes written to the file so far unless this stream is in append mode, in which case it will be equal to the size of the file. Writing bytes to this stream will increment the channel's position accordingly. Changing the channel's position, either explicitly or by writing, will change this stream's file position.

Returns:

the file channel associated with this file output stream

Since:

1.4