* Determines if a location is known to this file manager.
     *
     * @param location a location
     * @return true if the location is known
     */
    boolean hasLocation(Location location);

    /**
     * Gets a {@linkplain JavaFileObject file object} for input
     * representing the specified class of the specified kind in the
     * given location.
     *
     * @param location a location
     * @param className the name of a class
     * @param kind the kind of file, must be one of {@link
     * JavaFileObject.Kind#SOURCE SOURCE} or {@link
     * JavaFileObject.Kind#CLASS CLASS}
     * @return a file object, might return {@code null} if the
     * file 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 the kind 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
     */
    JavaFileObject getJavaFileForInput(Location location,
                                       String className,
                                       Kind kind)
        throws IOException;

    /**
     * Gets a {@linkplain JavaFileObject file object} for output
     * representing the specified class of the specified kind 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.
     *
     * @param location a location
     * @param className the name of a class
     * @param kind the kind of file, must be one of {@link
     * JavaFileObject.Kind#SOURCE SOURCE} or {@link
     * JavaFileObject.Kind#CLASS CLASS}
     * @param sibling a file object to be used as hint for placement;
     * might be {@code null}
     * @return a file object for output
     * @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 the kind 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 {@link #close} has been called
     * and this file manager cannot be reopened
     */
    JavaFileObject getJavaFileForOutput(Location location,
                                        String className,
                                        Kind kind,
                                        FileObject sibling)
        throws IOException;

    /**
     * Gets a {@linkplain FileObject file object} for input
     * representing the specified <a href="JavaFileManager.html#relative_name">relative
     * name</a> in the specified package in the given location.
     *
     * <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.  For example, to locate the properties file
     * "resources/compiler.properties" in the package
     * "com.sun.tools.javac" in the {@linkplain
     * StandardLocation#SOURCE_PATH SOURCE_PATH} location, this method
     * might be called like so:
     *
     * <pre>getFileForInput(SOURCE_PATH, "com.sun.tools.javac", "resources/compiler.properties");</pre>
     *
     * <p>If the call was executed on Windows, with SOURCE_PATH set to
     * <code>"C:\Documents and Settings\UncleBob\src\share\classes"</code>,
     * a valid result would be a file object representing the file
     * <code>"C:\Documents and Settings\UncleBob\src\share\classes\com\sun\tools\javac\resources\compiler.properties"</code>.

     *
     * @param location a location
     * @param packageName a package name
     * @param relativeName a relative name
     * @return a file object, might return {@code null} if the file