Group.java

/*
 * @(#)Group.java	1.21 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program 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.   
 *   
 * This program 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 at /legal/license.txt).   
 *   
 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.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 members();

}