/* * 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 interface is used to represent a group of principals. (A principal * represents an entity such as an individual user or a company). <p> * * Note that Group extends Principal. Thus, either a Principal or a Group can * be passed as an argument to methods containing a Principal parameter. For * example, you can add either a Principal or a Group to a Group object by * calling the object's <code>addMember</code> method, passing it the * Principal or Group. * * @author      Satish Dharmaraj */public interface Group extends Principal {     /**     * Adds the specified member to the group.     *     * @param user the principal to add to this group.     *     * @return true if the member was successfully added,     * false if the principal was already a member.     */    public boolean addMember(Principal user);     /**     * Removes the specified member from the group.     *     * @param user the principal to remove from this group.     *     * @return true if the principal was removed, or     * false if the principal was not a member.     */    public boolean removeMember(Principal user);     /**     * Returns true if the passed principal is a member of the group.     * This method does a recursive search, so if a principal belongs to a     * group which is a member of this group, true is returned.     *     * @param member the principal whose membership is to be checked.     *     * @return true if the principal is a member of this group,     * false otherwise.     */    public boolean isMember(Principal member);      /**     * Returns an enumeration of the members in the group.     * The returned objects can be instances of either Principal     * or Group (which is a subclass of Principal).     *     * @return an enumeration of the group members.     */    public Enumeration<? extends Principal> members(); }