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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

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 * 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,

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 *

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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} 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();

}