Adds a permission object to the current collection of permission objects.
Returns an enumeration of all the Permission objects in the collection.
Checks to see if the specified permission is implied by the collection of Permission objects held in this PermissionCollection.
Returns true if this PermissionCollection object is marked as readonly. If it is readonly, no new Permission objects can be added to it using {@code add}.
Marks this PermissionCollection object as "readonly". After a PermissionCollection object is marked as readonly, no new Permission objects can be added to it using {@code add}.
Returns a string describing this PermissionCollection object, providing information about all the permissions it contains. The format is: <pre> super.toString() ( // enumerate all the Permission // objects and call toString() on them, // one per line.. )</pre>
Abstract class representing a collection of Permission objects.
<p>With a PermissionCollection, you can: <UL> <LI> add a permission to the collection using the {@code add} method. <LI> check to see if a particular permission is implied in the collection, using the {@code implies} method. <LI> enumerate all the permissions, using the {@code elements} method. </UL>
<p>When it is desirable to group together a number of Permission objects of the same type, the {@code newPermissionCollection} method on that particular type of Permission object should first be called. The default behavior (from the Permission class) is to simply return null. Subclasses of class Permission override the method if they need to store their permissions in a particular PermissionCollection object in order to provide the correct semantics when the {@code PermissionCollection.implies} method is called. If a non-null value is returned, that PermissionCollection must be used. If null is returned, then the caller of {@code newPermissionCollection} is free to store permissions of the given type in any PermissionCollection they choose (one that uses a Hashtable, one that uses a Vector, etc).
<p>The PermissionCollection returned by the {@code Permission.newPermissionCollection} method is a homogeneous collection, which stores only Permission objects for a given Permission type. A PermissionCollection may also be heterogeneous. For example, Permissions is a PermissionCollection subclass that represents a collection of PermissionCollections. That is, its members are each a homogeneous PermissionCollection. For example, a Permissions object might have a FilePermissionCollection for all the FilePermission objects, a SocketPermissionCollection for all the SocketPermission objects, and so on. Its {@code add} method adds a permission to the appropriate collection.
<p>Whenever a permission is added to a heterogeneous PermissionCollection such as Permissions, and the PermissionCollection doesn't yet contain a PermissionCollection of the specified permission's type, the PermissionCollection should call the {@code newPermissionCollection} method on the permission's class to see if it requires a special PermissionCollection. If {@code newPermissionCollection} returns null, the PermissionCollection is free to store the permission in any type of PermissionCollection it desires (one using a Hashtable, one using a Vector, etc.). For example, the Permissions object uses a default PermissionCollection implementation that stores the permission objects in a Hashtable.
<p> Subclass implementations of PermissionCollection should assume that they may be called simultaneously from multiple threads, and therefore should be synchronized properly. Furthermore, Enumerations returned via the {@code elements} method are not <em>fail-fast</em>. Modifications to a collection should not be performed while enumerating over that collection.
@see Permission @see Permissions