src/share/classes/java/nio/file/attribute/BasicFileAttributes.java

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package java.nio.file.attribute;

/**
 * Basic attributes associated with a file in a file system.
 *
 * <p> Basic file attributes are attributes that are common to many file systems
 * and consist of mandatory and optional file attributes as defined by this
 * interface.
 *
 * <p> <b>Usage Example:</b>
 * <pre>
 *    FileRef file = ...
 *    BasicFileAttributes attrs = Attributes.readBasicFileAttributes(file);
 * </pre>
 *
 * @since 1.7
 *
 * @see BasicFileAttributeView
 */

public interface BasicFileAttributes {

    /**
     * Returns the time of last modification.
     *
     * @return  a {@code FileTime} representing the time the file was last
     *          modified or {@code null} if the attribute is not supported.
     */
    FileTime lastModifiedTime();

    /**
     * Returns the time of last access if supported.
     *
     * @return  a {@code FileTime} representing the time of last access or
     *          {@code null} if the attribute is not supported.
     */
    FileTime lastAccessTime();

    /**
     * Returns the creation time if supported. The creation time is the time
     * that the file was created.
     *
     * @return   a {@code FileTime} representing the time  the file was created
     *           or {@code null} if the attribute is not supported.
     */
    FileTime creationTime();

    /**
     * Tells whether the file is a regular file with opaque content.
     */
    boolean isRegularFile();

    /**
     * Tells whether the file is a directory.
     */
    boolean isDirectory();

    /**
     * Tells whether the file is a symbolic link.
     */
    boolean isSymbolicLink();

    /**
     * Tells whether the file is something other than a regular file, directory,
     * or symbolic link.
     */
    boolean isOther();

    /**
     * Returns the size of the file (in bytes). The size may differ from the
     * actual size on the file system due to compression, support for sparse
     * files, or other reasons. The size of files that are not {@link
     * #isRegularFile regular} files is implementation specific and
     * therefore unspecified.
     *
     * @return  the file size, in bytes
     */
    long size();

    /**
     * Returns an object that uniquely identifies the given file, or {@code
     * null} if a file key is not available. On some platforms or file systems
     * it is possible to use an identifier, or a combination of identifiers to
     * uniquely identify a file. Such identifiers are important for operations
     * such as file tree traversal in file systems that support <a
     * href="../package-summary.html#links">symbolic links</a> or file systems
     * that allow a file to be an entry in more than one directory. On UNIX file
     * systems, for example, the <em>device ID</em> and <em>inode</em> are
     * commonly used for such purposes.
     *
     * <p> The file key returned by this method can only be guaranteed to be
     * unique if the file system and files remain static. Whether a file system
     * re-uses identifiers after a file is deleted is implementation dependent and
     * therefore unspecified.
     *
     * <p> File keys returned by this method can be compared for equality and are
     * suitable for use in collections. If the file system and files remain static,
     * and two files are the {@link java.nio.file.Path#isSameFile same} with
     * non-{@code null} file keys, then their file keys are equal.
     *
     * @see java.nio.file.Files#walkFileTree
     */
    Object fileKey();
}