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FileOutputStream.javaAPI DocJava SE 5 API13423Fri Aug 26 14:56:58 BST 2005java.io

FileOutputStream

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.

author
Arthur van Hoff
version
1.57, 12/19/03
see
java.io.File
see
java.io.FileDescriptor
see
java.io.FileInputStream
since
JDK1.0

Fields Summary
private FileDescriptor
fd
The system dependent file descriptor. The value is 1 more than actual file descriptor. This means that the default value 0 indicates that the file is not open.
private FileChannel
channel
private boolean
append
Constructors Summary
public FileOutputStream(String name)
Creates an output file 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.

param
name the system-dependent filename
exception
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
exception
SecurityException if a security manager exists and its checkWrite method denies write access to the file.
see
java.lang.SecurityManager#checkWrite(java.lang.String)


                                                                                                                                                                                                                                 
         
	this(name != null ? new File(name) : null, false);
    
public FileOutputStream(String name, boolean append)
Creates an output file 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.

param
name the system-dependent file name
param
append if true, then bytes will be written to the end of the file rather than the beginning
exception
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.
exception
SecurityException if a security manager exists and its checkWrite method denies write access to the file.
see
java.lang.SecurityManager#checkWrite(java.lang.String)
since
JDK1.1

        this(name != null ? new File(name) : null, append);
    
public FileOutputStream(File file)
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.

param
file the file to be opened for writing.
exception
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
exception
SecurityException if a security manager exists and its checkWrite method denies write access to the file.
see
java.io.File#getPath()
see
java.lang.SecurityException
see
java.lang.SecurityManager#checkWrite(java.lang.String)

	this(file, false);
    
public FileOutputStream(File file, boolean append)
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.

param
file the file to be opened for writing.
param
append if true, then bytes will be written to the end of the file rather than the beginning
exception
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
exception
SecurityException if a security manager exists and its checkWrite method denies write access to the file.
see
java.io.File#getPath()
see
java.lang.SecurityException
see
java.lang.SecurityManager#checkWrite(java.lang.String)
since
1.4

        String name = (file != null ? file.getPath() : null);
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkWrite(name);
	}
        if (name == null) {
            throw new NullPointerException();
        }
	fd = new FileDescriptor();
        this.append = append;
	if (append) {
	    openAppend(name);
	} else {
	    open(name);
	}
    
public FileOutputStream(FileDescriptor fdObj)
Creates an output file 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.

param
fdObj the file descriptor to be opened for writing
exception
SecurityException if a security manager exists and its checkWrite method denies write access to the file descriptor
see
java.lang.SecurityManager#checkWrite(java.io.FileDescriptor)

	SecurityManager security = System.getSecurityManager();
	if (fdObj == null) {
	    throw new NullPointerException();
	}
	if (security != null) {
	    security.checkWrite(fdObj);
	}
	fd = fdObj;
    
Methods Summary
public voidclose()
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.

exception
IOException if an I/O error occurs.
revised
1.4
spec
JSR-51

        if (channel != null)
            channel.close();
        close0();
    
private native voidclose0()

protected voidfinalize()
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.

exception
IOException if an I/O error occurs.
see
java.io.FileInputStream#close()

 	if (fd != null) {
 	    if (fd == fd.out || fd == fd.err) {
 		flush();
 	    } else {
 		close();
 	    }
 	}
    
public java.nio.channels.FileChannelgetChannel()
Returns the unique {@link java.nio.channels.FileChannel FileChannel} object associated with this file output stream.

The initial {@link java.nio.channels.FileChannel#position() 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.

return
the file channel associated with this file output stream
since
1.4
spec
JSR-51

	synchronized (this) {
	    if (channel == null)
		channel = FileChannelImpl.open(fd, false, true, this, append);
	    return channel;
	}
    
public final java.io.FileDescriptorgetFD()
Returns the file descriptor associated with this stream.

return
the FileDescriptor object that represents the connection to the file in the file system being used by this FileOutputStream object.
exception
IOException if an I/O error occurs.
see
java.io.FileDescriptor

	if (fd != null) return fd;
	throw new IOException();
     
private static native voidinitIDs()

private native voidopen(java.lang.String name)
Opens a file, with the specified name, for writing.

param
name name of file to be opened

private native voidopenAppend(java.lang.String name)
Opens a file, with the specified name, for appending.

param
name name of file to be opened

public voidwrite(byte[] b)
Writes b.length bytes from the specified byte array to this file output stream.

param
b the data.
exception
IOException if an I/O error occurs.

	writeBytes(b, 0, b.length);
    
public voidwrite(byte[] b, int off, int len)
Writes len bytes from the specified byte array starting at offset off to this file output stream.

param
b the data.
param
off the start offset in the data.
param
len the number of bytes to write.
exception
IOException if an I/O error occurs.

	writeBytes(b, off, len);
    
public native voidwrite(int b)
Writes the specified byte to this file output stream. Implements the write method of OutputStream.

param
b the byte to be written.
exception
IOException if an I/O error occurs.

private native voidwriteBytes(byte[] b, int off, int len)
Writes a sub array as a sequence of bytes.

param
b the data to be written
param
off the start offset in the data
param
len the number of bytes that are written
exception
IOException If an I/O error has occurred.