Permissions (Java Platform SE 8 )
Keywords: java.security.Permissions class
Date: 2016-07-28

compact1, compact2, compact3
java.security

## Class Permissions

- java.lang.Object
- - java.security.PermissionCollection
  - - java.security.Permissions

- All Implemented Interfaces:
    Serializable

      public final class Permissions
      extends PermissionCollection
      implements Serializable

  This class represents a heterogeneous collection of Permissions. That is, it contains different types of Permission objects, organized into PermissionCollections. For example, if any `java.io.FilePermission` objects are added to an instance of this class, they are all stored in a single PermissionCollection. It is the PermissionCollection returned by a call to the `newPermissionCollection` method in the FilePermission class. Similarly, any `java.lang.RuntimePermission` objects are stored in the PermissionCollection returned by a call to the `newPermissionCollection` method in the RuntimePermission class. Thus, this class represents a collection of PermissionCollections.

  When the `add` method is called to add a Permission, the Permission is stored in the appropriate PermissionCollection. If no such collection exists yet, the Permission object's class is determined and the `newPermissionCollection` method is called on that class to create the PermissionCollection and add it to the Permissions object. If `newPermissionCollection` returns null, then a default PermissionCollection that uses a hashtable will be created and used. Each hashtable entry stores a Permission object as both the key and the value.

  Enumerations returned via the `elements` method are not fail-fast. Modifications to a collection should not be performed while enumerating over that collection.

  See Also:
    `Permission`, `PermissionCollection`, `AllPermission`

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `Permissions()` Creates a new Permissions object containing no PermissionCollections.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `add(Permission permission)` Adds a permission object to the PermissionCollection for the class the permission belongs to.
    `Enumeration<Permission>` | `elements()` Returns an enumeration of all the Permission objects in all the PermissionCollections in this Permissions object.
    `boolean` | `implies(Permission permission)` Checks to see if this object's PermissionCollection for permissions of the specified permission's class implies the permissions expressed in the permission object.

    - ### Methods inherited from class java.security.PermissionCollection

      `isReadOnly, setReadOnly, toString`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

- - ### Constructor Detail

    - #### Permissions

          public Permissions()

      Creates a new Permissions object containing no PermissionCollections.

  - ### Method Detail

    - #### add

          public void add(Permission permission)

      Adds a permission object to the PermissionCollection for the class the permission belongs to. For example, if permission is a FilePermission, it is added to the FilePermissionCollection stored in this Permissions object. This method creates a new PermissionCollection object (and adds the permission to it) if an appropriate collection does not yet exist.

      Specified by:
        `add` in class `PermissionCollection`
      Parameters:
        `permission` - the Permission object to add.
      Throws:
        `SecurityException` - if this Permissions object is marked as readonly.
      See Also:
        `PermissionCollection.isReadOnly()`

    - #### implies

          public boolean implies(Permission permission)

      Checks to see if this object's PermissionCollection for permissions of the specified permission's class implies the permissions expressed in the permission object. Returns true if the combination of permissions in the appropriate PermissionCollection (e.g., a FilePermissionCollection for a FilePermission) together imply the specified permission.

      For example, suppose there is a FilePermissionCollection in this Permissions object, and it contains one FilePermission that specifies "read" access for all files in all subdirectories of the "/tmp" directory, and another FilePermission that specifies "write" access for all files in the "/tmp/scratch/foo" directory. Then if the `implies` method is called with a permission specifying both "read" and "write" access to files in the "/tmp/scratch/foo" directory, `true` is returned.

      Additionally, if this PermissionCollection contains the AllPermission, this method will always return true.

      Specified by:
        `implies` in class `PermissionCollection`
      Parameters:
        `permission` - the Permission object to check.
      Returns:
        true if "permission" is implied by the permissions in the PermissionCollection it belongs to, false if not.

    - #### elements

          public Enumeration<Permission> elements()

      Returns an enumeration of all the Permission objects in all the PermissionCollections in this Permissions object.
      Specified by:
        `elements` in class `PermissionCollection`
      Returns:
        an enumeration of all the Permissions.

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