/* * Copyright (c) 1996, 2004, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.security.acl; import java.util.Enumeration;import java.security.Principal; /** * This is the interface used for representing one entry in an Access * Control List (ACL).<p> * * An ACL can be thought of as a data structure with multiple ACL entry * objects. Each ACL entry object contains a set of permissions associated * with a particular principal. (A principal represents an entity such as * an individual user or a group). Additionally, each ACL entry is specified * as being either positive or negative. If positive, the permissions are * to be granted to the associated principal. If negative, the permissions * are to be denied. Each principal can have at most one positive ACL entry * and one negative entry; that is, multiple positive or negative ACL * entries are not allowed for any principal. * * Note: ACL entries are by default positive. An entry becomes a * negative entry only if the * {@link #setNegativePermissions() setNegativePermissions} * method is called on it. * * @see java.security.acl.Acl * * @author      Satish Dharmaraj */public interface AclEntry extends Cloneable {     /**     * Specifies the principal for which permissions are granted or denied     * by this ACL entry. If a principal was already set for this ACL entry,     * false is returned, otherwise true is returned.     *     * @param user the principal to be set for this entry.     *     * @return true if the principal is set, false if there was     * already a principal set for this entry.     *     * @see #getPrincipal     */    public boolean setPrincipal(Principal user);     /**     * Returns the principal for which permissions are granted or denied by     * this ACL entry. Returns null if there is no principal set for this     * entry yet.     *     * @return the principal associated with this entry.     *     * @see #setPrincipal     */    public Principal getPrincipal();     /**     * Sets this ACL entry to be a negative one. That is, the associated     * principal (e.g., a user or a group) will be denied the permission set     * specified in the entry.     *     * Note: ACL entries are by default positive. An entry becomes a     * negative entry only if this <code>setNegativePermissions</code>     * method is called on it.     */    public void setNegativePermissions();     /**     * Returns true if this is a negative ACL entry (one denying the     * associated principal the set of permissions in the entry), false     * otherwise.     *     * @return true if this is a negative ACL entry, false if it's not.     */    public boolean isNegative();     /**     * Adds the specified permission to this ACL entry. Note: An entry can     * have multiple permissions.     *     * @param permission the permission to be associated with     * the principal in this entry.     *     * @return true if the permission was added, false if the     * permission was already part of this entry's permission set.     */    public boolean addPermission(Permission permission);     /**     * Removes the specified permission from this ACL entry.     *     * @param permission the permission to be removed from this entry.     *     * @return true if the permission is removed, false if the     * permission was not part of this entry's permission set.     */    public boolean removePermission(Permission permission);     /**     * Checks if the specified permission is part of the     * permission set in this entry.     *     * @param permission the permission to be checked for.     *     * @return true if the permission is part of the     * permission set in this entry, false otherwise.     */    public boolean checkPermission(Permission permission);     /**     * Returns an enumeration of the permissions in this ACL entry.     *     * @return an enumeration of the permissions in this ACL entry.     */    public Enumeration<Permission> permissions();     /**     * Returns a string representation of the contents of this ACL entry.     *     * @return a string representation of the contents.     */    public String toString();     /**     * Clones this ACL entry.     *     * @return a clone of this ACL entry.     */    public Object clone();}