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 {@code 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.
*
* @apiNote
* To release resources used by this stream {@link #close} should be called
* directly or by try-with-resources. Subclasses are responsible for the cleanup
* of resources acquired by the subclass.
* Subclasses that override {@link #finalize} in order to perform cleanup
* should be modified to use alternative cleanup mechanisms such as
* {@link java.lang.ref.Cleaner} and remove the overriding {@code finalize} method.
*
* @implSpec
* If this FileOutputStream has been subclassed and the {@link #close}
* method has been overridden, the {@link #close} method will be
* called when the FileInputStream is unreachable.
* Otherwise, it is implementation specific how the resource cleanup described in
* {@link #close} is performed.
*
* @author Arthur van Hoff
* @see java.io.File
* @see java.io.FileDescriptor
* @see java.io.FileInputStream
* @see java.nio.file.Files#newOutputStream
* @since 1.0
*/
public
class FileOutputStream extends OutputStream
{
/**
* Access to FileDescriptor internals.
*/
private static final JavaIOFileDescriptorAccess fdAccess =
SharedSecrets.getJavaIOFileDescriptorAccess();
/**
* The system dependent file descriptor.
*/
private final FileDescriptor fd;
/**
* The associated channel, initialized lazily.
*/
private volatile FileChannel channel;
/**
* The path of the referenced file
* (null if the stream is created with a file descriptor)
*/
private final String path;
private final Object closeLock = new Object();
private volatile boolean closed;
/**
* 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.
*
* @implSpec Invoking this constructor with the parameter {@code name} is
* equivalent to invoking {@link #FileOutputStream(String,boolean)
* new FileOutputStream(name, false)}.
*
* @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)
*/
public FileOutputStream(String name) throws FileNotFoundException {
this(name != null ? new File(name) : null, false);
}
/**
* 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.
*
* @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 1.1
*/
public FileOutputStream(String name, boolean append)
throws FileNotFoundException
{
this(name != null ? new File(name) : null, append);
}
/**
* 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)
*/
public FileOutputStream(File file) throws FileNotFoundException {
this(file, false);
}
/**
* 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
*/
public FileOutputStream(File file, boolean append)
throws FileNotFoundException
{
String name = (file != null ? file.getPath() : null);
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkWrite(name);
}
if (name == null) {
throw new NullPointerException();
}
if (file.isInvalid()) {
throw new FileNotFoundException("Invalid file path");
}
this.fd = new FileDescriptor();
fd.attach(this);
this.path = name;
open(name, append);
FileCleanable.register(fd); // open sets the fd, register the cleanup
}
/**
* 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 {@link java.io.FileDescriptor#valid() invalid}.
* However, if the methods are invoked on the resulting stream to attempt
* I/O on the stream, an IOException is thrown.
*
* @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)
*/
public FileOutputStream(FileDescriptor fdObj) {
SecurityManager security = System.getSecurityManager();
if (fdObj == null) {
throw new NullPointerException();
}
if (security != null) {
security.checkWrite(fdObj);
}
this.fd = fdObj;
this.path = null;
fd.attach(this);
}
/**
* Opens a file, with the specified name, for overwriting or appending.
* @param name name of file to be opened
* @param append whether the file is to be opened in append mode
*/
private native void open0(String name, boolean append)
throws FileNotFoundException;
// wrap native call to allow instrumentation
/**
* Opens a file, with the specified name, for overwriting or appending.
* @param name name of file to be opened
* @param append whether the file is to be opened in append mode
*/
private void open(String name, boolean append)
throws FileNotFoundException {
open0(name, append);
}
/**
* Writes the specified byte to this file output stream.
*
* @param b the byte to be written.
* @param append {@code 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. Implements
* the write method of OutputStream.
*
* @param b the byte to be written.
* @exception IOException if an I/O error occurs.
*/
public void write(int b) throws IOException {
write(b, fdAccess.getAppend(fd));
}
/**
* 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
* @param append {@code true} to first advance the position to the
* end of file
* @exception IOException If an I/O error has occurred.
*/
private native void writeBytes(byte b[], int off, int len, boolean append)
throws IOException;
/**
* 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.
*/
public void write(byte b[]) throws IOException {
writeBytes(b, 0, b.length, fdAccess.getAppend(fd));
}
/**
* 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.
*/
public void write(byte b[], int off, int len) throws IOException {
writeBytes(b, off, len, fdAccess.getAppend(fd));
}
/**
* 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.
*
* @apiNote
* Overriding {@link #close} to perform cleanup actions is reliable
* only when called directly or when called by try-with-resources.
* Do not depend on finalization to invoke {@code close};
* finalization is not reliable and is deprecated.
* If cleanup of native resources is needed, other mechanisms such as
* {@linkplain java.lang.ref.Cleaner} should be used.
*
* @exception IOException if an I/O error occurs.
*
* @revised 1.4
* @spec JSR-51
*/
public void close() throws IOException {
if (closed) {
return;
}
synchronized (closeLock) {
if (closed) {
return;
}
closed = true;
}
FileChannel fc = channel;
if (fc != null) {
// possible race with getChannel(), benign since
// FileChannel.close is final and idempotent
fc.close();
}
fd.closeAll(new Closeable() {
public void close() throws IOException {
fd.close();
}
});
}
/**
* 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
*/
public final FileDescriptor getFD() throws IOException {
if (fd != null) {
return fd;
}
throw new IOException();
}
/**
* 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 */ public FileChannel getChannel() { FileChannel fc = this.channel; if (fc == null) { synchronized (this) { fc = this.channel; if (fc == null) { this.channel = fc = FileChannelImpl.open(fd, path, false, true, false, this); if (closed) { try { // possible race with close(), benign since // FileChannel.close is final and idempotent fc.close(); } catch (IOException ioe) { throw new InternalError(ioe); // should not happen } } } } } return fc; } private static native void initIDs(); static { initIDs(); } }