* does not exist
     * @throws IllegalArgumentException if the location is not known
     * to this file manager and the file manager does not support
     * unknown locations, or if {@code relativeName} is not valid
     * @throws IOException if an I/O error occurred, or if {@link
     * #close} has been called and this file manager cannot be
     * reopened
     * @throws IllegalStateException if {@link #close} has been called
     * and this file manager cannot be reopened
     */
    FileObject getFileForInput(Location location,
                               String packageName,
                               String relativeName)
        throws IOException;

    /**
     * Gets a {@linkplain FileObject file object} for output
     * representing the specified <a href="JavaFileManager.html#relative_name">relative
     * name</a> in the specified package in the given location.
     *
     * <p>Optionally, this file manager might consider the sibling as
     * a hint for where to place the output.  The exact semantics of
     * this hint is unspecified.  Sun's compiler, javac, for
     * example, will place class files in the same directories as
     * originating source files unless a class file output directory
     * is provided.  To facilitate this behavior, javac might provide
     * the originating source file as sibling when calling this
     * method.
     *
     * <p>If the returned object represents a {@linkplain
     * JavaFileObject.Kind#SOURCE source} or {@linkplain
     * JavaFileObject.Kind#CLASS class} file, it must be an instance
     * of {@link JavaFileObject}.
     *
     * <p>Informally, the file object returned by this method is
     * located in the concatenation of the location, package name, and
     * relative name or next to the sibling argument.  See {@link
     * #getFileForInput getFileForInput} for an example.
     *
     * @param location a location
     * @param packageName a package name
     * @param relativeName a relative name
     * @param sibling a file object to be used as hint for placement;
     * might be {@code null}
     * @return a file object
     * @throws IllegalArgumentException if sibling is not known to
     * this file manager, or if the location is not known to this file
     * manager and the file manager does not support unknown
     * locations, or if {@code relativeName} is not valid
     * @throws IOException if an I/O error occurred, or if {@link
     * #close} has been called and this file manager cannot be
     * reopened
     * @throws IllegalStateException if {@link #close} has been called
     * and this file manager cannot be reopened
     */
    FileObject getFileForOutput(Location location,
                                String packageName,
                                String relativeName,
                                FileObject sibling)
        throws IOException;

    /**
     * Flushes any resources opened for output by this file manager
     * directly or indirectly.  Flushing a closed file manager has no
     * effect.
     *
     * @throws IOException if an I/O error occurred
     * @see #close
     */
    void flush() throws IOException;

    /**
     * Releases any resources opened by this file manager directly or
     * indirectly.  This might render this file manager useless and
     * the effect of subsequent calls to methods on this object or any
     * objects obtained through this object is undefined unless
     * explicitly allowed.  However, closing a file manager which has
     * already been closed has no effect.
     *
     * @throws IOException if an I/O error occurred
     * @see #flush
     */
    void close() throws IOException;
}