Module java.base
Package java.io

Class FileOutputStream

java.lang.Object
java.io.OutputStream
java.io.FileOutputStream
All Implemented Interfaces:
Closeable,Flushable,AutoCloseable
public classFileOutputStreamextendsOutputStream
A file output stream is an output stream for writing data to aFile or to aFileDescriptor. 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 oneFileOutputStream (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 usingFileWriter.

API Note:
To release resources used by this streamclose() should be called directly or by try-with-resources. Subclasses are responsible for the cleanup of resources acquired by the subclass. Subclasses that overrideObject.finalize() in order to perform cleanup should be modified to use alternative cleanup mechanisms such asCleaner and remove the overridingfinalize method.
Implementation Requirements:
If this FileOutputStream has been subclassed and theclose() method has been overridden, theclose() method will be called when the FileInputStream is unreachable. Otherwise, it is implementation specific how the resource cleanup described inclose() is performed.
Since:
1.0
See Also:

  • Constructor Summary

    Constructors
    Constructor
    Description
    Creates a file output stream to write to the file represented by the specifiedFile object.
    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 specifiedFile object.
    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
    Closes this file output stream and releases any system resources associated with this stream.
    Returns the uniqueFileChannel object associated with this file output stream.
    Returns the file descriptor associated with this stream.
    void
    write(byte[] b)
    Writesb.length bytes from the specified byte array to this file output stream.
    void
    write(byte[] b, int off, int len)
    Writeslen bytes from the specified byte array starting at offsetoff 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

  • Constructor Details

    • FileOutputStream

      public FileOutputStream(String name) throwsFileNotFoundException
      Creates a file output stream to write to the file with the specified name. A newFileDescriptor object is created to represent this file connection.

      First, if there is a security manager, itscheckWrite method is called withname 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 aFileNotFoundException is thrown.

      Implementation Requirements:
      Invoking this constructor with the parametername is equivalent to invokingnew 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 itscheckWrite method denies write access to the file.
      See Also:

    • FileOutputStream

      public FileOutputStream(String name, boolean append) throwsFileNotFoundException
      Creates a file output stream to write to the file with the specified name. If the second argument istrue, then bytes will be written to the end of the file rather than the beginning. A newFileDescriptor object is created to represent this file connection.

      First, if there is a security manager, itscheckWrite method is called withname 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 aFileNotFoundException is thrown.

      Parameters:
      name - the system-dependent file name
      append - iftrue, 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 itscheckWrite method denies write access to the file.
      Since:
      1.1
      See Also:

    • FileOutputStream

      public FileOutputStream(File file) throwsFileNotFoundException
      Creates a file output stream to write to the file represented by the specifiedFile object. A newFileDescriptor object is created to represent this file connection.

      First, if there is a security manager, itscheckWrite method is called with the path represented by thefile 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 aFileNotFoundException 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 itscheckWrite method denies write access to the file.
      See Also:

    • FileOutputStream

      public FileOutputStream(File file, boolean append) throwsFileNotFoundException
      Creates a file output stream to write to the file represented by the specifiedFile object. If the second argument istrue, then bytes will be written to the end of the file rather than the beginning. A newFileDescriptor object is created to represent this file connection.

      First, if there is a security manager, itscheckWrite method is called with the path represented by thefile 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 aFileNotFoundException is thrown.

      Parameters:
      file - the file to be opened for writing.
      append - iftrue, 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 itscheckWrite method denies write access to the file.
      Since:
      1.4
      See Also:

    • 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, itscheckWrite method is called with the file descriptorfdObj argument as its argument.

      IffdObj is null then aNullPointerException is thrown.

      This constructor does not throw an exception iffdObj isinvalid. However, if the methods are invoked on the resulting stream to attempt I/O on the stream, anIOException is thrown.

      Parameters:
      fdObj - the file descriptor to be opened for writing
      Throws:
      SecurityException - if a security manager exists and itscheckWrite method denies write access to the file descriptor
      See Also:

  • Method Details

    • write

      public void write(int b) throwsIOException
      Writes the specified byte to this file output stream. Implements thewrite method ofOutputStream.
      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) throwsIOException
      Writesb.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:

    • write

      public void write(byte[] b, int off, int len) throwsIOException
      Writeslen bytes from the specified byte array starting at offsetoff 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() throwsIOException
      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:
      Overridingclose() to perform cleanup actions is reliable only when called directly or when called by try-with-resources. Do not depend on finalization to invokeclose; finalization is not reliable and is deprecated. If cleanup of native resources is needed, other mechanisms such asCleaner should be used.
      Throws:
      IOException - if an I/O error occurs.

    • getFD

      public final FileDescriptor getFD() throwsIOException
      Returns the file descriptor associated with this stream.
      Returns:
      theFileDescriptor object that represents the connection to the file in the file system being used by thisFileOutputStream object.
      Throws:
      IOException - if an I/O error occurs.
      See Also:

    • getChannel

      public FileChannel getChannel()
      Returns the uniqueFileChannel object associated with this file output stream.

      The initialposition 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