OpenJDK 27 · java.io.FileOutputStream · APIdia, the JavaDoc alternative

Modifier and Type	Field and Description
private volatile FileChannel	channel The associated channel, initialized lazily.
private volatile boolean	closed
private final Object	closeLock
private final FileDescriptor	fd The system dependent file descriptor.
private static final JavaIOFileDescriptorAccess	FD_ACCESS Access to FileDescriptor internals.
private static boolean	jfrTracing Flag set by jdk.internal.event.JFRTracing to indicate if file writes should be traced by JFR.
private final String	path The path of the referenced file (null if the stream is created with a file descriptor)

Constructor Summary

Access	Constructor and Description
public	FileOutputStream(String the system-dependent filename name) Creates a file output stream to write to the file with the specified name.
public	FileOutputStream(String the system-dependent file name name, boolean if `true`, then bytes will be written to the end of the file rather than the beginning append) Creates a file output stream to write to the file with the specified name.
public	FileOutputStream(File the file to be opened for writing. file) Creates a file output stream to write to the file represented by the specified `File` object.
public	FileOutputStream(File the file to be opened for writing. file, boolean if `true`, then bytes will be written to the end of the file rather than the beginning append) Creates a file output stream to write to the file represented by the specified `File` object.
public	FileOutputStream(FileDescriptor the file descriptor to be opened for writing 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.

Method Summary

Modifier and Type	Method and Description
public void	close() Overrides java.io.OutputStream.close. Implements java.io.Closeable.close. Closes this file output stream and releases any system resources associated with this stream.
public FileChannel	Returns: the file channel associated with this file output stream getChannel() Returns the unique `FileChannel` object associated with this file output stream.
public final FileDescriptor	Returns: the `FileDescriptor` object that represents the connection to the file in the file system being used by this `FileOutputStream` object. getFD() Returns the file descriptor associated with this stream.
private static native void	initIDs()
private void	open(String name of file to be opened name, boolean whether the file is to be opened in append mode append) Opens a file, with the specified name, for overwriting or appending.
private native void	open0(String name of file to be opened name, boolean whether the file is to be opened in append mode append) Opens a file, with the specified name, for overwriting or appending.
private void	traceWrite(int b, boolean append)
private void	traceWriteBytes(byte[] b, int off, int len, boolean append)
private native void	write(int the byte to be written. b, boolean `true` if the write operation first advances the position to the end of file append) Writes the specified byte to this file output stream.
public void	write(int the byte to be written. b) Implements abstract java.io.OutputStream.write. Writes the specified byte to this file output stream.
public void	write(byte[] b) Overrides java.io.OutputStream.write. Writes `b.length` bytes from the specified byte array to this file output stream.
public void	write(byte[] b, int off, int len) Overrides java.io.OutputStream.write. Writes `len` bytes from the specified byte array starting at offset `off` to this file output stream.
private native void	writeBytes(byte[] the data to be written b, int the start offset in the data off, int the number of bytes that are written len, boolean `true` to first advance the position to the end of file append) Writes a sub array as a sequence of bytes.

Inherited from java.io.OutputStream:: flush nullOutputStream

Field Detail

channel	back to summary
private volatile FileChannel channel The associated channel, initialized lazily.

closed	back to summary
private volatile boolean closed

closeLock	back to summary
private final Object closeLock

fd	back to summary
private final FileDescriptor fd The system dependent file descriptor.

FD_ACCESS	back to summary
private static final JavaIOFileDescriptorAccess FD_ACCESS Access to FileDescriptor internals.

jfrTracing	back to summary
private static boolean jfrTracing Flag set by jdk.internal.event.JFRTracing to indicate if file writes should be traced by JFR.

path	back to summary
private final String path The path of the referenced file (null if the stream is created with a file descriptor)

Constructor Detail

FileOutputStream back to summary

FileOutputStream	back to summary
public FileOutputStream(String name) throws FileNotFoundException Creates a file output stream to write to the file with the specified name. If the file exists, it is truncated, otherwise a new file is created. Symbolic links are automatically redirected to the target of the link. A new `FileDescriptor` object is created to represent this file connection. 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 Specification Invoking this constructor with the parameter `name` is equivalent to invoking `new FileOutputStream(name, false)`. Parameters name:String the system-dependent filename Exceptions 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

public FileOutputStream(String name) throws FileNotFoundException

Creates a file output stream to write to the file with the specified name. If the file exists, it is truncated, otherwise a new file is created. Symbolic links are automatically redirected to the target of the link. A new FileDescriptor object is created to represent this file connection.

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 Specification

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

Parameters

name:String: the system-dependent filename

Exceptions

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

FileOutputStream back to summary

FileOutputStream	back to summary
public FileOutputStream(String name, boolean append) throws FileNotFoundException Creates a file output stream to write to the file with the specified name. If the file exists, it is truncated unless the second argument is `true`, in which case bytes will be written to the end of the file rather than the beginning. If the file does not exist, it is created. Symbolic links are automatically redirected to the target of the link. A new `FileDescriptor` object is created to represent this file connection. 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:String the system-dependent file name append:boolean if `true`, then bytes will be written to the end of the file rather than the beginning Exceptions 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. Since 1.1

public FileOutputStream(String name, boolean append) throws FileNotFoundException

Creates a file output stream to write to the file with the specified name. If the file exists, it is truncated unless the second argument is true, in which case bytes will be written to the end of the file rather than the beginning. If the file does not exist, it is created. Symbolic links are automatically redirected to the target of the link. A new FileDescriptor object is created to represent this file connection.

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:String: the system-dependent file name
append:boolean: if true, then bytes will be written to the end of the file rather than the beginning

Exceptions

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.

Since

1.1

FileOutputStream back to summary

FileOutputStream	back to summary
public FileOutputStream(File file) throws FileNotFoundException Creates a file output stream to write to the file represented by the specified `File` object. If the file exists, it is truncated, otherwise a new file is created. Symbolic links are automatically redirected to the target of the link. A new `FileDescriptor` object is created to represent this file connection. 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:File the file to be opened for writing. Exceptions 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 See Also `java.io.File#getPath()`

public FileOutputStream(File file) throws FileNotFoundException

Creates a file output stream to write to the file represented by the specified File object. If the file exists, it is truncated, otherwise a new file is created. Symbolic links are automatically redirected to the target of the link. A new FileDescriptor object is created to represent this file connection.

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:File: the file to be opened for writing.

Exceptions

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

See Also

java.io.File#getPath()

FileOutputStream back to summary

FileOutputStream	back to summary
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 file exists, it is truncated unless the second argument is `true`, in which case bytes will be written to the end of the file rather than the beginning. If the file does not exist, it is created. Symbolic links are automatically redirected to the target of the link. A new `FileDescriptor` object is created to represent this file connection. 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:File the file to be opened for writing. append:boolean if `true`, then bytes will be written to the end of the file rather than the beginning Annotations @SuppressWarnings:this-escape Exceptions 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 Since 1.4 See Also `java.io.File#getPath()`

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 file exists, it is truncated unless the second argument is true, in which case bytes will be written to the end of the file rather than the beginning. If the file does not exist, it is created. Symbolic links are automatically redirected to the target of the link. A new FileDescriptor object is created to represent this file connection.

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:File: the file to be opened for writing.
append:boolean: if true, then bytes will be written to the end of the file rather than the beginning

Annotations

@SuppressWarnings:this-escape

Exceptions

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

Since

1.4

See Also

java.io.File#getPath()

FileOutputStream back to summary

FileOutputStream	back to summary
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. 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:FileDescriptor the file descriptor to be opened for writing Annotations @SuppressWarnings:this-escape

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.

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:FileDescriptor: the file descriptor to be opened for writing

Annotations

@SuppressWarnings:this-escape

Method Detail

close back to summary

close	back to summary
public void close() throws IOException Overrides java.io.OutputStream.close. Implements java.io.Closeable.close. 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. API Note Overriding `close` to perform cleanup actions is reliable only when called directly or when called by try-with-resources. Implementation Specification Subclasses requiring that resource cleanup take place after a stream becomes unreachable should use the `java.lang.ref.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. Annotations @Override Exceptions IOException: if an I/O error occurs.

public void close() throws IOException

Overrides java.io.OutputStream.close.

Implements java.io.Closeable.close.

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.

API Note

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

Implementation Specification

Subclasses requiring that resource cleanup take place after a stream becomes unreachable should use the java.lang.ref.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.

Annotations

@Override

Exceptions

IOException:: if an I/O error occurs.

getChannel back to summary

getChannel	back to summary
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:FileChannel the file channel associated with this file output stream Since 1.4

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:FileChannel: the file channel associated with this file output stream
Since: 1.4

getFD back to summary

getFD	back to summary
public final FileDescriptor getFD() throws IOException Returns the file descriptor associated with this stream. Returns:FileDescriptor the `FileDescriptor` object that represents the connection to the file in the file system being used by this `FileOutputStream` object. Exceptions IOException: if an I/O error occurs. See Also `java.io.FileDescriptor`

public final FileDescriptor getFD() throws IOException

Returns the file descriptor associated with this stream.

Returns:FileDescriptor

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

Exceptions

IOException:: if an I/O error occurs.

See Also

java.io.FileDescriptor

initIDs	back to summary
private static native void initIDs()

open	back to summary
private void open(String name, boolean append) throws FileNotFoundException Opens a file, with the specified name, for overwriting or appending. Parameters name:String name of file to be opened append:boolean whether the file is to be opened in append mode

open

back to summary

private void open(String name, boolean append) throws FileNotFoundException

Opens a file, with the specified name, for overwriting or appending.

Parameters

name:String: name of file to be opened
append:boolean: whether the file is to be opened in append mode

open0	back to summary
private native void open0(String name, boolean append) throws FileNotFoundException Opens a file, with the specified name, for overwriting or appending. Parameters name:String name of file to be opened append:boolean whether the file is to be opened in append mode

open0

back to summary

private native void open0(String name, boolean append) throws FileNotFoundException

Opens a file, with the specified name, for overwriting or appending.

Parameters

name:String: name of file to be opened
append:boolean: whether the file is to be opened in append mode

traceWrite	back to summary
private void traceWrite(int b, boolean append) throws IOException

traceWriteBytes	back to summary
private void traceWriteBytes(byte[] b, int off, int len, boolean append) throws IOException

write back to summary

write	back to summary
private native void write(int b, boolean append) throws IOException Writes the specified byte to this file output stream. Parameters b:int the byte to be written. append:boolean `true` if the write operation first advances the position to the end of file

private native void write(int b, boolean append) throws IOException

Writes the specified byte to this file output stream.

Parameters

b:int: the byte to be written.
append:boolean: true if the write operation first advances the position to the end of file

write back to summary

write	back to summary
public void write(int b) throws IOException Implements abstract java.io.OutputStream.write. Writes the specified byte to this file output stream. Implements the `write` method of `OutputStream`. Parameters b:int the byte to be written. Annotations @Override Exceptions IOException: if an I/O error occurs.

public void write(int b) throws IOException

Implements abstract java.io.OutputStream.write.

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

Parameters

b:int: the byte to be written.

Annotations

@Override

Exceptions

IOException:: if an I/O error occurs.

write back to summary

write	back to summary
public void write(byte[] b) throws IOException Overrides java.io.OutputStream.write. Writes `b.length` bytes from the specified byte array to this file output stream. Annotations @Override Exceptions IOException: if an I/O error occurs.

public void write(byte[] b) throws IOException

Overrides java.io.OutputStream.write.

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

Annotations

@Override

Exceptions

IOException:: if an I/O error occurs.

write back to summary

write	back to summary
public void write(byte[] b, int off, int len) throws IOException Overrides java.io.OutputStream.write. Writes `len` bytes from the specified byte array starting at offset `off` to this file output stream. Annotations @Override Exceptions IOException: if an I/O error occurs. IndexOutOfBoundsException: If `off` is negative, `len` is negative, or `len` is greater than `b.length - off`

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

Overrides java.io.OutputStream.write.

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

Annotations

@Override

Exceptions

IOException:: if an I/O error occurs.
IndexOutOfBoundsException:: If off is negative, len is negative, or len is greater than b.length - off

writeBytes back to summary

writeBytes	back to summary
private native void writeBytes(byte[] b, int off, int len, boolean append) throws IOException Writes a sub array as a sequence of bytes. Parameters b:byte[] the data to be written off:int the start offset in the data len:int the number of bytes that are written append:boolean `true` to first advance the position to the end of file Exceptions IOException: If an I/O error has occurred.

private native void writeBytes(byte[] b, int off, int len, boolean append) throws IOException

Writes a sub array as a sequence of bytes.

Parameters

b:byte[]: the data to be written
off:int: the start offset in the data
len:int: the number of bytes that are written
append:boolean: true to first advance the position to the end of file

Exceptions

IOException:: If an I/O error has occurred.

public Class FileOutputStream

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail