Group (Java Platform SE 8 )
Keywords: java.security.acl.Group interface
Date: 2026-04-17

compact3
java.security.acl

## Interface Group

- All Superinterfaces:
    Principal

      public interface Group
      extends Principal

  This interface is used to represent a group of principals. (A principal represents an entity such as an individual user or a company).

  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 `addMember` method, passing it the Principal or Group.

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `addMember(Principal user)` Adds the specified member to the group.
    `boolean` | `isMember(Principal member)` Returns true if the passed principal is a member of the group.
    `Enumeration<? extends Principal>` | `members()` Returns an enumeration of the members in the group.
    `boolean` | `removeMember(Principal user)` Removes the specified member from the group.

    - ### Methods inherited from interface java.security.Principal

      `equals, getName, hashCode, implies, toString`

- - ### Method Detail

    - #### addMember

          boolean addMember(Principal user)

      Adds the specified member to the group.
      Parameters:
        `user` - the principal to add to this group.
      Returns:
        true if the member was successfully added, false if the principal was already a member.

    - #### removeMember

          boolean removeMember(Principal user)

      Removes the specified member from the group.
      Parameters:
        `user` - the principal to remove from this group.
      Returns:
        true if the principal was removed, or false if the principal was not a member.

    - #### isMember

          boolean isMember(Principal member)

      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.
      Parameters:
        `member` - the principal whose membership is to be checked.
      Returns:
        true if the principal is a member of this group, false otherwise.

    - #### members

          Enumeration<? extends Principal> members()

      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).
      Returns:
        an enumeration of the group members.

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