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.
+ *
+ *
+ * First, if there is a security manager, its
+ * 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
+ * First, if there is a security manager, its
+ * 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
+ * First, if there is a security manager, its
+ * 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
+ * First, if there is a security manager, its
+ * 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
+ * First, if there is a security manager, its
+ * If
+ * This constructor does not throw an exception if 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
+ */
+ public void close() throws IOException {
+ synchronized (closeLock) {
+ if (closed) {
+ return;
+ }
+ closed = true;
+ }
+
+ if (channel != null) {
+ /*
+ * Decrement FD use count associated with the channel
+ * The use count is incremented whenever a new channel
+ * is obtained from this stream.
+ */
+ fd.decrementAndGetUseCount();
+ channel.close();
+ }
+
+ /*
+ * Decrement FD use count associated with this stream
+ */
+ int useCount = fd.decrementAndGetUseCount();
+
+ /*
+ * If FileDescriptor is still in use by another stream, the finalizer
+ * will not close it.
+ */
+ if ((useCount <= 0) || !isRunningFinalize()) {
+ close0();
+ }
+ }
+
+ /**
+ * Returns the file descriptor associated with this stream.
+ *
+ * @return the The initial {@link java.nio.channels.FileChannel#position()
+ * positionFileOutputStream is meant for writing streams of raw bytes
+ * such as image data. For writing streams of characters, consider using
+ * FileWriter.
+ *
+ * @author Arthur van Hoff
+ * @see java.io.File
+ * @see java.io.FileDescriptor
+ * @see java.io.FileInputStream
+ * @see java.nio.file.Files#newOutputStream
+ * @since JDK1.0
+ */
+public
+class FileOutputStream extends OutputStream
+{
+ /**
+ * The system dependent file descriptor.
+ */
+ private final FileDescriptor fd;
+
+ /**
+ * True if the file is opened for append.
+ */
+ private final boolean append;
+
+ /**
+ * The associated channel, initalized lazily.
+ */
+ private FileChannel channel;
+
+ private final Object closeLock = new Object();
+ private volatile boolean closed = false;
+ private static final ThreadLocalFileDescriptor object is
+ * created to represent this file connection.
+ * checkWrite
+ * method is called with name as its argument.
+ * 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)
+ */
+ 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.
+ * checkWrite
+ * method is called with name as its argument.
+ * 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
+ */
+ 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.
+ * checkWrite
+ * method is called with the path represented by the file
+ * argument as its argument.
+ * 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.
+ * checkWrite
+ * method is called with the path represented by the file
+ * argument as its argument.
+ * 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();
+ }
+ this.fd = new FileDescriptor();
+ this.append = append;
+
+ fd.incrementAndGetUseCount();
+ open(name, append);
+ }
+
+ /**
+ * 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.
+ * checkWrite
+ * method is called with the file descriptor fdObj
+ * argument as its argument.
+ * fdObj is null then a NullPointerException
+ * is thrown.
+ * 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.append = false;
+
+ /*
+ * FileDescriptor is being shared by streams.
+ * Ensure that it's GC'ed only when all the streams/channels are done
+ * using it.
+ */
+ fd.incrementAndGetUseCount();
+ }
+
+ /**
+ * 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 open(String name, boolean append)
+ throws FileNotFoundException;
+
+ /**
+ * 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, append);
+ }
+
+ /**
+ * 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, append);
+ }
+
+ /**
+ * 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, append);
+ }
+
+ /**
+ * 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.
+ *
+ * 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. } 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() {
+ synchronized (this) {
+ if (channel == null) {
+ channel = FileChannelImpl.open(fd, false, true, append, this);
+
+ /*
+ * Increment fd's use count. Invoking the channel's close()
+ * method will result in decrementing the use count set for
+ * the channel.
+ */
+ fd.incrementAndGetUseCount();
+ }
+ return channel;
+ }
+ }
+
+ /**
+ * 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()
+ */
+ protected void finalize() throws IOException {
+ if (fd != null) {
+ if (fd == FileDescriptor.out || fd == FileDescriptor.err) {
+ flush();
+ } else {
+
+ /*
+ * Finalizer should not release the FileDescriptor if another
+ * stream is still using it. If the user directly invokes
+ * close() then the FileDescriptor is also released.
+ */
+ runningFinalize.set(Boolean.TRUE);
+ try {
+ close();
+ } finally {
+ runningFinalize.set(Boolean.FALSE);
+ }
+ }
+ }
+ }
+
+ private native void close0() throws IOException;
+
+ private static native void initIDs();
+
+ static {
+ initIDs();
+ }
+
+}