compact1, compact2, compact3
java.security

## Class AccessControlContext

- java.lang.Object
- - java.security.AccessControlContext

-     public final class AccessControlContext
      extends Object

  An AccessControlContext is used to make system resource access decisions based on the context it encapsulates.

  More specifically, it encapsulates a context and has a single method, `checkPermission`, that is equivalent to the `checkPermission` method in the AccessController class, with one difference: The AccessControlContext `checkPermission` method makes access decisions based on the context it encapsulates, rather than that of the current execution thread.

  Thus, the purpose of AccessControlContext is for those situations where a security check that should be made within a given context actually needs to be done from within a different context (for example, from within a worker thread).

  An AccessControlContext is created by calling the `AccessController.getContext` method. The `getContext` method takes a "snapshot" of the current calling context, and places it in an AccessControlContext object, which it returns. A sample call is the following:

         AccessControlContext acc = AccessController.getContext()

  Code within a different context can subsequently call the `checkPermission` method on the previously-saved AccessControlContext object. A sample call is the following:

         acc.checkPermission(permission)

  See Also:
    `AccessController`

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `AccessControlContext(AccessControlContext acc, DomainCombiner combiner)` Create a new `AccessControlContext` with the given `AccessControlContext` and `DomainCombiner`.
    `AccessControlContext(ProtectionDomain[] context)` Create an AccessControlContext with the given array of ProtectionDomains.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `checkPermission(Permission perm)` Determines whether the access request indicated by the specified permission should be allowed or denied, based on the security policy currently in effect, and the context in this object.
    `boolean` | `equals(Object obj)` Checks two AccessControlContext objects for equality.
    `DomainCombiner` | `getDomainCombiner()` Get the `DomainCombiner` associated with this `AccessControlContext`.
    `int` | `hashCode()` Returns the hash code value for this context.

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

      `clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### AccessControlContext

          public AccessControlContext(ProtectionDomain[] context)

      Create an AccessControlContext with the given array of ProtectionDomains. Context must not be null. Duplicate domains will be removed from the context.
      Parameters:
        `context` - the ProtectionDomains associated with this context. The non-duplicate domains are copied from the array. Subsequent changes to the array will not affect this AccessControlContext.
      Throws:
        `NullPointerException` - if `context` is `null`

    - #### AccessControlContext

          public AccessControlContext(AccessControlContext acc,
                                      DomainCombiner combiner)

      Create a new `AccessControlContext` with the given `AccessControlContext` and `DomainCombiner`. This constructor associates the provided `DomainCombiner` with the provided `AccessControlContext`.

      Parameters:
        `acc` - the `AccessControlContext` associated with the provided `DomainCombiner`.
        `combiner` - the `DomainCombiner` to be associated with the provided `AccessControlContext`.
      Throws:
        `NullPointerException` - if the provided `context` is `null`.
        `SecurityException` - if a security manager is installed and the caller does not have the "createAccessControlContext" `SecurityPermission`
      Since:
        1.3

  - ### Method Detail

    - #### getDomainCombiner

          public DomainCombiner getDomainCombiner()

      Get the `DomainCombiner` associated with this `AccessControlContext`.

      Returns:
        the `DomainCombiner` associated with this `AccessControlContext`, or `null` if there is none.
      Throws:
        `SecurityException` - if a security manager is installed and the caller does not have the "getDomainCombiner" `SecurityPermission`
      Since:
        1.3

    - #### checkPermission

          public void checkPermission(Permission perm)
                               throws AccessControlException

      Determines whether the access request indicated by the specified permission should be allowed or denied, based on the security policy currently in effect, and the context in this object. The request is allowed only if every ProtectionDomain in the context implies the permission. Otherwise the request is denied.

      This method quietly returns if the access request is permitted, or throws a suitable AccessControlException otherwise.

      Parameters:
        `perm` - the requested permission.
      Throws:
        `AccessControlException` - if the specified permission is not permitted, based on the current security policy and the context encapsulated by this object.
        `NullPointerException` - if the permission to check for is null.

    - #### equals

          public boolean equals(Object obj)

      Checks two AccessControlContext objects for equality. Checks that obj is an AccessControlContext and has the same set of ProtectionDomains as this context.

      Overrides:
        `equals` in class `Object`
      Parameters:
        `obj` - the object we are testing for equality with this object.
      Returns:
        true if obj is an AccessControlContext, and has the same set of ProtectionDomains as this context, false otherwise.
      See Also:
        `Object.hashCode()`, `HashMap`

    - #### hashCode

          public int hashCode()

      Returns the hash code value for this context. The hash code is computed by exclusive or-ing the hash code of all the protection domains in the context together.
      Overrides:
        `hashCode` in class `Object`
      Returns:
        a hash code value for this context.
      See Also:
        `Object.equals(java.lang.Object)`, `System.identityHashCode(java.lang.Object)`

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