# Subject Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary:[Ctors](https://developer.android.com/reference/javax/security/auth/Subject#pubctors)\|[Methods](https://developer.android.com/reference/javax/security/auth/Subject#pubmethods)\|[Inherited Methods](https://developer.android.com/reference/javax/security/auth/Subject#inhmethods) # Subject ` public final class Subject ` ` extends `[Object](https://developer.android.com/reference/java/lang/Object)` `` implements `[Serializable](https://developer.android.com/reference/java/io/Serializable)` ` |---|-----------------------------| | [java.lang.Object](https://developer.android.com/reference/java/lang/Object) || | ↳ | javax.security.auth.Subject |
*** ** * ** ***
A`Subject`represents a grouping of related information for a single entity, such as a person. Such information includes the Subject's identities as well as its security-related attributes (passwords and cryptographic keys, for example). Subjects may potentially have multiple identities. Each identity is represented as a`Principal`within the`Subject`. Principals simply bind names to a`Subject`. For example, a`Subject`that happens to be a person, Alice, might have two Principals: one which binds "Alice Bar", the name on her driver license, to the`Subject`, and another which binds, "999-99-9999", the number on her student identification card, to the`Subject`. Both Principals refer to the same`Subject`even though each has a different name. A`Subject`may also own security-related attributes, which are referred to as credentials. Sensitive credentials that require special protection, such as private cryptographic keys, are stored within a private credential`Set`. Credentials intended to be shared, such as public key certificates or Kerberos server tickets are stored within a public credential`Set`. Different permissions are required to access and modify the different credential Sets. To retrieve all the Principals associated with a`Subject`, invoke the`getPrincipals`method. To retrieve all the public or private credentials belonging to a`Subject`, invoke the`getPublicCredentials`method or`getPrivateCredentials`method, respectively. To modify the returned`Set`of Principals and credentials, use the methods defined in the`Set`class. For example: ``` Subject subject; Principal principal; Object credential; // add a Principal and credential to the Subject subject.getPrincipals().add(principal); subject.getPublicCredentials().add(credential); ``` This`Subject`class implements`Serializable`. While the Principals associated with the`Subject`are serialized, the credentials associated with the`Subject`are not. Note that the`java.security.Principal`class does not implement`Serializable`. Therefore all concrete`Principal`implementations associated with Subjects must implement`Serializable`. **See also:** - [Principal](https://developer.android.com/reference/java/security/Principal) - [DomainCombiner](https://developer.android.com/reference/java/security/DomainCombiner) ## Summary | ### Public constructors || |------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---| | ` `[Subject](https://developer.android.com/reference/javax/security/auth/Subject#Subject())`() ` Create an instance of a`Subject`with an empty`Set`of Principals and empty Sets of public and private credentials. | | ` `[Subject](https://developer.android.com/reference/javax/security/auth/Subject#Subject(boolean,%20java.util.Set,%20java.util.Set,%20java.util.Set))`(boolean readOnly, `[Set](https://developer.android.com/reference/java/util/Set)` principals, `[Set](https://developer.android.com/reference/java/util/Set)` pubCredentials, `[Set](https://developer.android.com/reference/java/util/Set)` privCredentials) ` Create an instance of a`Subject`with Principals and credentials. | | ### Public methods || |-----------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` static T` | ` `[doAs](https://developer.android.com/reference/javax/security/auth/Subject#doAs(javax.security.auth.Subject,%20java.security.PrivilegedExceptionAction))`(`[Subject](https://developer.android.com/reference/javax/security/auth/Subject)` subject, `[PrivilegedExceptionAction](https://developer.android.com/reference/java/security/PrivilegedExceptionAction)` action) ` Perform work as a particular`Subject`. | | ` static T` | ` `[doAs](https://developer.android.com/reference/javax/security/auth/Subject#doAs(javax.security.auth.Subject,%20java.security.PrivilegedAction))`(`[Subject](https://developer.android.com/reference/javax/security/auth/Subject)` subject, `[PrivilegedAction](https://developer.android.com/reference/java/security/PrivilegedAction)` action) ` Perform work as a particular`Subject`. | | ` static T` | ` `[doAsPrivileged](https://developer.android.com/reference/javax/security/auth/Subject#doAsPrivileged(javax.security.auth.Subject,%20java.security.PrivilegedExceptionAction,%20java.security.AccessControlContext))`(`[Subject](https://developer.android.com/reference/javax/security/auth/Subject)` subject, `[PrivilegedExceptionAction](https://developer.android.com/reference/java/security/PrivilegedExceptionAction)` action, `[AccessControlContext](https://developer.android.com/reference/java/security/AccessControlContext)` acc) ` Perform privileged work as a particular`Subject`. | | ` static T` | ` `[doAsPrivileged](https://developer.android.com/reference/javax/security/auth/Subject#doAsPrivileged(javax.security.auth.Subject,%20java.security.PrivilegedAction,%20java.security.AccessControlContext))`(`[Subject](https://developer.android.com/reference/javax/security/auth/Subject)` subject, `[PrivilegedAction](https://developer.android.com/reference/java/security/PrivilegedAction)` action, `[AccessControlContext](https://developer.android.com/reference/java/security/AccessControlContext)` acc) ` Perform privileged work as a particular`Subject`. | | ` boolean` | ` `[equals](https://developer.android.com/reference/javax/security/auth/Subject#equals(java.lang.Object))`(`[Object](https://developer.android.com/reference/java/lang/Object)` o) ` Compares the specified Object with this`Subject`for equality. | | ` `[Set](https://developer.android.com/reference/java/util/Set)`<`[Principal](https://developer.android.com/reference/java/security/Principal)`>` | ` `[getPrincipals](https://developer.android.com/reference/javax/security/auth/Subject#getPrincipals())`() ` Return the`Set`of Principals associated with this`Subject`. | | ` `[Set](https://developer.android.com/reference/java/util/Set)`` | ` `[getPrincipals](https://developer.android.com/reference/javax/security/auth/Subject#getPrincipals(java.lang.Class))`(`[Class](https://developer.android.com/reference/java/lang/Class)` c) ` Return a`Set`of Principals associated with this`Subject`that are instances or subclasses of the specified`Class`. | | ` `[Set](https://developer.android.com/reference/java/util/Set)`` | ` `[getPrivateCredentials](https://developer.android.com/reference/javax/security/auth/Subject#getPrivateCredentials(java.lang.Class))`(`[Class](https://developer.android.com/reference/java/lang/Class)` c) ` Return a`Set`of private credentials associated with this`Subject`that are instances or subclasses of the specified`Class`. | | ` `[Set](https://developer.android.com/reference/java/util/Set)`<`[Object](https://developer.android.com/reference/java/lang/Object)`>` | ` `[getPrivateCredentials](https://developer.android.com/reference/javax/security/auth/Subject#getPrivateCredentials())`() ` Return the`Set`of private credentials held by this`Subject`. | | ` `[Set](https://developer.android.com/reference/java/util/Set)`<`[Object](https://developer.android.com/reference/java/lang/Object)`>` | ` `[getPublicCredentials](https://developer.android.com/reference/javax/security/auth/Subject#getPublicCredentials())`() ` Return the`Set`of public credentials held by this`Subject`. | | ` `[Set](https://developer.android.com/reference/java/util/Set)`` | ` `[getPublicCredentials](https://developer.android.com/reference/javax/security/auth/Subject#getPublicCredentials(java.lang.Class))`(`[Class](https://developer.android.com/reference/java/lang/Class)` c) ` Return a`Set`of public credentials associated with this`Subject`that are instances or subclasses of the specified`Class`. | | ` static `[Subject](https://developer.android.com/reference/javax/security/auth/Subject) | ` `[getSubject](https://developer.android.com/reference/javax/security/auth/Subject#getSubject(java.security.AccessControlContext))`(`[AccessControlContext](https://developer.android.com/reference/java/security/AccessControlContext)` acc) ` Get the`Subject`associated with the provided`AccessControlContext`. | | ` int` | ` `[hashCode](https://developer.android.com/reference/javax/security/auth/Subject#hashCode())`() ` Returns a hashcode for this`Subject`. | | ` boolean` | ` `[isReadOnly](https://developer.android.com/reference/javax/security/auth/Subject#isReadOnly())`() ` Query whether this`Subject`is read-only. | | ` void` | ` `[setReadOnly](https://developer.android.com/reference/javax/security/auth/Subject#setReadOnly())`() ` Set this`Subject`to be read-only. | | ` `[String](https://developer.android.com/reference/java/lang/String) | ` `[toString](https://developer.android.com/reference/javax/security/auth/Subject#toString())`() ` Return the String representation of this`Subject`. | | ### Inherited methods | |-----------------------|---| | From class` `[java.lang.Object](https://developer.android.com/reference/java/lang/Object)` ` |--------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` `[Object](https://developer.android.com/reference/java/lang/Object) | ` `[clone](https://developer.android.com/reference/java/lang/Object#clone())`() ` Creates and returns a copy of this object. | | ` boolean` | ` `[equals](https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object))`(`[Object](https://developer.android.com/reference/java/lang/Object)` obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` `[finalize](https://developer.android.com/reference/java/lang/Object#finalize())`() ` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | | ` final `[Class](https://developer.android.com/reference/java/lang/Class)`` | ` `[getClass](https://developer.android.com/reference/java/lang/Object#getClass())`() ` Returns the runtime class of this`Object`. | | ` int` | ` `[hashCode](https://developer.android.com/reference/java/lang/Object#hashCode())`() ` Returns a hash code value for the object. | | ` final void` | ` `[notify](https://developer.android.com/reference/java/lang/Object#notify())`() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` `[notifyAll](https://developer.android.com/reference/java/lang/Object#notifyAll())`() ` Wakes up all threads that are waiting on this object's monitor. | | ` `[String](https://developer.android.com/reference/java/lang/String) | ` `[toString](https://developer.android.com/reference/java/lang/Object#toString())`() ` Returns a string representation of the object. | | ` final void` | ` `[wait](https://developer.android.com/reference/java/lang/Object#wait(long,%20int))`(long timeoutMillis, int nanos) ` Causes the current thread to wait until it is awakened, typically by being*notified* or*interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` `[wait](https://developer.android.com/reference/java/lang/Object#wait(long))`(long timeoutMillis) ` Causes the current thread to wait until it is awakened, typically by being*notified* or*interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` `[wait](https://developer.android.com/reference/java/lang/Object#wait())`() ` Causes the current thread to wait until it is awakened, typically by being*notified* or*interrupted*. | || ## Public constructors ### Subject Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public Subject () ``` Create an instance of a`Subject`with an empty`Set`of Principals and empty Sets of public and private credentials. The newly constructed Sets check whether this`Subject`has been set read-only before permitting subsequent modifications. The newly created Sets also prevent illegal modifications by ensuring that callers have sufficient permissions. To modify the Principals Set, the caller must have`AuthPermission("modifyPrincipals")`. To modify the public credential Set, the caller must have`AuthPermission("modifyPublicCredentials")`. To modify the private credential Set, the caller must have`AuthPermission("modifyPrivateCredentials")`.
### Subject Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public Subject (boolean readOnly, Set principals, Set pubCredentials, Set privCredentials) ``` Create an instance of a`Subject`with Principals and credentials. The Principals and credentials from the specified Sets are copied into newly constructed Sets. These newly created Sets check whether this`Subject`has been set read-only before permitting subsequent modifications. The newly created Sets also prevent illegal modifications by ensuring that callers have sufficient permissions. To modify the Principals Set, the caller must have`AuthPermission("modifyPrincipals")`. To modify the public credential Set, the caller must have`AuthPermission("modifyPublicCredentials")`. To modify the private credential Set, the caller must have`AuthPermission("modifyPrivateCredentials")`.

| Parameters || |-------------------|-----------------------------------------------------------------------------------| | `readOnly` | `boolean`: true if the`Subject`is to be read-only, and false otherwise.
| | `principals` | `Set`: the`Set`of Principals to be associated with this`Subject`.
| | `pubCredentials` | `Set`: the`Set`of public credentials to be associated with this`Subject`.
| | `privCredentials` | `Set`: the`Set`of private credentials to be associated with this`Subject`.
| | Throws || |------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------| | [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if the specified`principals`,`pubCredentials`, or`privCredentials`are`null`. | ## Public methods ### doAs Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public static T doAs (Subject subject, PrivilegedExceptionAction action) ``` Perform work as a particular`Subject`. This method first retrieves the current Thread's`AccessControlContext`via`AccessController.getContext`, and then instantiates a new`AccessControlContext`using the retrieved context along with a new`SubjectDomainCombiner`(constructed using the provided`Subject`). Finally, this method invokes`AccessController.doPrivileged`, passing it the provided`PrivilegedExceptionAction`, as well as the newly constructed`AccessControlContext`.

| Parameters || |-----------|---------------------------------------------------------------------------------------------------| | `subject` | `Subject`: the`Subject`that the specified`action`will run as. This parameter may be`null`.
| | `action` | `PrivilegedExceptionAction`: the code to be run as the specified`Subject`.
| | Returns || |-----|--------------------------------------------------------------------------| | `T` | the value returned by the PrivilegedExceptionAction's`run`method.
| | Throws || |--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------| | [PrivilegedActionException](https://developer.android.com/reference/java/security/PrivilegedActionException) | if the`PrivilegedExceptionAction.run`method throws a checked exception.
| | [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if the specified`PrivilegedExceptionAction`is`null`.
| | [SecurityException](https://developer.android.com/reference/java/lang/SecurityException) | if the caller does not have permission to invoke this method. | ### doAs Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public static T doAs (Subject subject, PrivilegedAction action) ``` Perform work as a particular`Subject`. This method first retrieves the current Thread's`AccessControlContext`via`AccessController.getContext`, and then instantiates a new`AccessControlContext`using the retrieved context along with a new`SubjectDomainCombiner`(constructed using the provided`Subject`). Finally, this method invokes`AccessController.doPrivileged`, passing it the provided`PrivilegedAction`, as well as the newly constructed`AccessControlContext`.

| Parameters || |-----------|---------------------------------------------------------------------------------------------------| | `subject` | `Subject`: the`Subject`that the specified`action`will run as. This parameter may be`null`.
| | `action` | `PrivilegedAction`: the code to be run as the specified`Subject`.
| | Returns || |-----|-----------------------------------------------------------------| | `T` | the value returned by the PrivilegedAction's`run`method.
| | Throws || |------------------------------------------------------------------------------------------------|---------------------------------------------------------------| | [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if the`PrivilegedAction`is`null`.
| | [SecurityException](https://developer.android.com/reference/java/lang/SecurityException) | if the caller does not have permission to invoke this method. | ### doAsPrivileged Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public static T doAsPrivileged (Subject subject, PrivilegedExceptionAction action, AccessControlContext acc) ``` Perform privileged work as a particular`Subject`. This method behaves exactly as`Subject.doAs`, except that instead of retrieving the current Thread's`AccessControlContext`, it uses the provided`AccessControlContext`. If the provided`AccessControlContext`is`null`, this method instantiates a new`AccessControlContext`with an empty collection of ProtectionDomains.

| Parameters || |-----------|------------------------------------------------------------------------------------------------------------| | `subject` | `Subject`: the`Subject`that the specified`action`will run as. This parameter may be`null`.
| | `action` | `PrivilegedExceptionAction`: the code to be run as the specified`Subject`.
| | `acc` | `AccessControlContext`: the`AccessControlContext`to be tied to the specified*subject* and*action* .
| | Returns || |-----|--------------------------------------------------------------------------| | `T` | the value returned by the PrivilegedExceptionAction's`run`method.
| | Throws || |--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------| | [PrivilegedActionException](https://developer.android.com/reference/java/security/PrivilegedActionException) | if the`PrivilegedExceptionAction.run`method throws a checked exception.
| | [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if the specified`PrivilegedExceptionAction`is`null`.
| | [SecurityException](https://developer.android.com/reference/java/lang/SecurityException) | if the caller does not have permission to invoke this method. | ### doAsPrivileged Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public static T doAsPrivileged (Subject subject, PrivilegedAction action, AccessControlContext acc) ``` Perform privileged work as a particular`Subject`. This method behaves exactly as`Subject.doAs`, except that instead of retrieving the current Thread's`AccessControlContext`, it uses the provided`AccessControlContext`. If the provided`AccessControlContext`is`null`, this method instantiates a new`AccessControlContext`with an empty collection of ProtectionDomains.

| Parameters || |-----------|------------------------------------------------------------------------------------------------------------| | `subject` | `Subject`: the`Subject`that the specified`action`will run as. This parameter may be`null`.
| | `action` | `PrivilegedAction`: the code to be run as the specified`Subject`.
| | `acc` | `AccessControlContext`: the`AccessControlContext`to be tied to the specified*subject* and*action* .
| | Returns || |-----|-----------------------------------------------------------------| | `T` | the value returned by the PrivilegedAction's`run`method.
| | Throws || |------------------------------------------------------------------------------------------------|---------------------------------------------------------------| | [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if the`PrivilegedAction`is`null`.
| | [SecurityException](https://developer.android.com/reference/java/lang/SecurityException) | if the caller does not have permission to invoke this method. | ### equals Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public boolean equals (Object o) ``` Compares the specified Object with this`Subject`for equality. Returns true if the given object is also a Subject and the two`Subject`instances are equivalent. More formally, two`Subject`instances are equal if their`Principal`and`Credential`Sets are equal.

| Parameters || |-----|-------------------------------------------------------------------------| | `o` | `Object`: Object to be compared for equality with this`Subject`.
| | Returns || |-----------|----------------------------------------------------------------| | `boolean` | true if the specified Object is equal to this`Subject`.
| | Throws || |------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | [SecurityException](https://developer.android.com/reference/java/lang/SecurityException) | if the caller does not have permission to access the private credentials for this`Subject`, or if the caller does not have permission to access the private credentials for the provided`Subject`. | ### getPrincipals Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public Set getPrincipals () ``` Return the`Set`of Principals associated with this`Subject`. Each`Principal`represents an identity for this`Subject`. The returned`Set`is backed by this Subject's internal`Principal``Set`. Any modification to the returned`Set`affects the internal`Principal``Set`as well.

| Returns || |------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------| | [Set](https://developer.android.com/reference/java/util/Set)`<`[Principal](https://developer.android.com/reference/java/security/Principal)`>` | The`Set`of Principals associated with this`Subject`.
| ### getPrincipals Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public Set getPrincipals (Class c) ``` Return a`Set`of Principals associated with this`Subject`that are instances or subclasses of the specified`Class`. The returned`Set`is not backed by this Subject's internal`Principal``Set`. A new`Set`is created and returned for each method invocation. Modifications to the returned`Set`will not affect the internal`Principal``Set`.

| Parameters || |-----|-------------------------------------------------------------------------------------| | `c` | `Class`: the returned`Set`of Principals will all be instances of this class.
| | Returns || |-------------------------------------------------------------------|------------------------------------------------------------------------| | [Set](https://developer.android.com/reference/java/util/Set)`` | a`Set`of Principals that are instances of the specified`Class`.
| | Throws || |------------------------------------------------------------------------------------------------|----------------------------------| | [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if the specified`Class`is`null`. | ### getPrivateCredentials Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public Set getPrivateCredentials (Class c) ``` Return a`Set`of private credentials associated with this`Subject`that are instances or subclasses of the specified`Class`. The caller must have permission to access all of the requested Credentials, or a`SecurityException`will be thrown. The returned`Set`is not backed by this Subject's internal private Credential`Set`. A new`Set`is created and returned for each method invocation. Modifications to the returned`Set`will not affect the internal private Credential`Set`.

| Parameters || |-----|----------------------------------------------------------------------------------------------| | `c` | `Class`: the returned`Set`of private credentials will all be instances of this class.
| | Returns || |-------------------------------------------------------------------|---------------------------------------------------------------------------------| | [Set](https://developer.android.com/reference/java/util/Set)`` | a`Set`of private credentials that are instances of the specified`Class`.
| | Throws || |------------------------------------------------------------------------------------------------|----------------------------------| | [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if the specified`Class`is`null`. | ### getPrivateCredentials Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public Set getPrivateCredentials () ``` Return the`Set`of private credentials held by this`Subject`. The returned`Set`is backed by this Subject's internal private Credential`Set`. Any modification to the returned`Set`affects the internal private Credential`Set`as well. A caller requires permissions to access the Credentials in the returned`Set`, or to modify the`Set`itself. A`SecurityException`is thrown if the caller does not have the proper permissions. While iterating through the`Set`, a`SecurityException`is thrown if the caller does not have permission to access a particular Credential. The`Iterator`is nevertheless advanced to next element in the`Set`.

| Returns || |--------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------| | [Set](https://developer.android.com/reference/java/util/Set)`<`[Object](https://developer.android.com/reference/java/lang/Object)`>` | A`Set`of private credentials held by this`Subject`.
| ### getPublicCredentials Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public Set getPublicCredentials () ``` Return the`Set`of public credentials held by this`Subject`. The returned`Set`is backed by this Subject's internal public Credential`Set`. Any modification to the returned`Set`affects the internal public Credential`Set`as well.

| Returns || |--------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------| | [Set](https://developer.android.com/reference/java/util/Set)`<`[Object](https://developer.android.com/reference/java/lang/Object)`>` | A`Set`of public credentials held by this`Subject`.
| ### getPublicCredentials Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public Set getPublicCredentials (Class c) ``` Return a`Set`of public credentials associated with this`Subject`that are instances or subclasses of the specified`Class`. The returned`Set`is not backed by this Subject's internal public Credential`Set`. A new`Set`is created and returned for each method invocation. Modifications to the returned`Set`will not affect the internal public Credential`Set`.

| Parameters || |-----|---------------------------------------------------------------------------------------------| | `c` | `Class`: the returned`Set`of public credentials will all be instances of this class.
| | Returns || |-------------------------------------------------------------------|--------------------------------------------------------------------------------| | [Set](https://developer.android.com/reference/java/util/Set)`` | a`Set`of public credentials that are instances of the specified`Class`.
| | Throws || |------------------------------------------------------------------------------------------------|----------------------------------| | [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if the specified`Class`is`null`. | ### getSubject Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public static Subject getSubject (AccessControlContext acc) ``` Get the`Subject`associated with the provided`AccessControlContext`. The`AccessControlContext`may contain many Subjects (from nested`doAs`calls). In this situation, the most recent`Subject`associated with the`AccessControlContext`is returned.

| Parameters || |-------|----------------------------------------------------------------------------------------------| | `acc` | `AccessControlContext`: the`AccessControlContext`from which to retrieve the`Subject`.
| | Returns || |--------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------| | [Subject](https://developer.android.com/reference/javax/security/auth/Subject) | the`Subject`associated with the provided`AccessControlContext`, or`null`if no`Subject`is associated with the provided`AccessControlContext`.
| | Throws || |------------------------------------------------------------------------------------------------|--------------------------------------------------------------------| | [SecurityException](https://developer.android.com/reference/java/lang/SecurityException) | if the caller does not have permission to get the`Subject`.
| | [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if the provided`AccessControlContext`is`null`. | ### hashCode Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public int hashCode () ``` Returns a hashcode for this`Subject`.

| Returns || |-------|--------------------------------------| | `int` | a hashcode for this`Subject`.
| | Throws || |------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------| | [SecurityException](https://developer.android.com/reference/java/lang/SecurityException) | if the caller does not have permission to access this Subject's private credentials. | ### isReadOnly Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public boolean isReadOnly () ``` Query whether this`Subject`is read-only.

| Returns || |-----------|------------------------------------------------------------| | `boolean` | true if this`Subject`is read-only, false otherwise.
| ### setReadOnly Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public void setReadOnly () ``` Set this`Subject`to be read-only. Modifications (additions and removals) to this Subject's`Principal``Set`and credential Sets will be disallowed. The`destroy`operation on this Subject's credentials will still be permitted. Subsequent attempts to modify the Subject's`Principal`and credential Sets will result in an`IllegalStateException`being thrown. Also, once a`Subject`is read-only, it can not be reset to being writable again.

| Throws || |------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------| | [SecurityException](https://developer.android.com/reference/java/lang/SecurityException) | if the caller does not have permission to set this`Subject`to be read-only. | ### toString Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public String toString () ``` Return the String representation of this`Subject`.

| Returns || |--------------------------------------------------------------------|----------------------------------------------------| | [String](https://developer.android.com/reference/java/lang/String) | the String representation of this`Subject`.
|