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:

  • 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:

    • 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:

    • 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:

    • 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:

    • 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:

  • 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:

    • 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:

    • 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