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`.

  Since:
    JDK1.0
  Author:
    Arthur van Hoff
  See Also:
    `File`, `FileDescriptor`, `FileInputStream`, `Files.newOutputStream(java.nio.file.Path, java.nio.file.OpenOption...)`

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `FileOutputStream(File file)` Creates a file output stream to write to the file represented by the specified `File` object.
    `FileOutputStream(File file, boolean append)` 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(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

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `close()` Closes this file output stream and releases any system resources associated with this stream.
    `protected void` | `finalize()` Cleans up the connection to the file, and ensures that the `close` method of this file output stream is called when there are no more references to this stream.
    `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 inherited from class java.io.OutputStream

      `flush`

    - ### Methods inherited from class java.lang.Object

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

- - ### Constructor Detail

    - #### 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.

      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:
        JDK1.1
      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 Detail

    - #### 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.

    - #### 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 `Closeable`
      Specified by:
        `close` in interface `AutoCloseable`
      Overrides:
        `close` in class `OutputStream`
      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`

    - #### finalize

          protected void finalize()
                           throws IOException

      Cleans up the connection to the file, and ensures that the `close` method of this file output stream is called when there are no more references to this stream.
      Overrides:
        `finalize` in class `Object`
      Throws:
        `IOException` - if an I/O error occurs.
      See Also:
        `FileInputStream.close()`

Copyright © 2025 API Design. All Rights Reserved.