Module java.base
Package java.lang

## Class SecurityManager

- java.lang.Object
- - java.lang.SecurityManager

- Direct Known Subclasses:
    `RMISecurityManager`

      public class SecurityManager
      extends Object

  The security manager is a class that allows applications to implement a security policy. It allows an application to determine, before performing a possibly unsafe or sensitive operation, what the operation is and whether it is being attempted in a security context that allows the operation to be performed. The application can allow or disallow the operation.

  The `SecurityManager` class contains many methods with names that begin with the word `check`. These methods are called by various methods in the Java libraries before those methods perform certain potentially sensitive operations. The invocation of such a `check` method typically looks like this:

  >          SecurityManager security = System.getSecurityManager();
  >          if (security != null) {
  >              security.checkXXX(argument,  . . . );
  >          }

  The security manager is thereby given an opportunity to prevent completion of the operation by throwing an exception. A security manager routine simply returns if the operation is permitted, but throws a `SecurityException` if the operation is not permitted.

  Environments using a security manager will typically set the security manager at startup. In the JDK implementation, this is done by setting the system property `java.security.manager` on the command line to the class name of the security manager. It can also be set to the empty String ("") or the special token "`default`" to use the default `java.lang.SecurityManager`. If a class name is specified, it must be `java.lang.SecurityManager` or a public subclass and have a public no-arg constructor. The class is loaded by the built-in system class loader if it is not `java.lang.SecurityManager`. If the `java.security.manager` system property is not set, the default value is `null`, which means a security manager will not be set at startup.

  The Java run-time may also allow, but is not required to allow, the security manager to be set dynamically by invoking the `setSecurityManager` method. In the JDK implementation, if the Java virtual machine is started with the `java.security.manager` system property set to the special token "`disallow`" then a security manager will not be set at startup and cannot be set dynamically (the `setSecurityManager` method will throw an `UnsupportedOperationException`). If the `java.security.manager` system property is not set or is set to the special token "`allow`", then a security manager will not be set at startup but can be set dynamically. Finally, if the `java.security.manager` system property is set to the class name of the security manager, or to the empty String ("") or the special token "`default`", then a security manager is set at startup (as described previously) and can also be subsequently replaced (or disabled) dynamically (subject to the policy of the currently installed security manager). The following table illustrates the behavior of the JDK implementation for the different settings of the `java.security.manager` system property:

  property value, the SecurityManager set at startup, can dynamically set a SecurityManager
  Property Value | The SecurityManager set at startup | System.setSecurityManager run-time behavior
  --- | --- | ---
  null | None | Success or throws `SecurityException` if not permitted by the currently installed security manager
  empty String ("") | `java.lang.SecurityManager` | Success or throws `SecurityException` if not permitted by the currently installed security manager
  "default" | `java.lang.SecurityManager` | Success or throws `SecurityException` if not permitted by the currently installed security manager
  "disallow" | None | Always throws `UnsupportedOperationException`
  "allow" | None | Success or throws `SecurityException` if not permitted by the currently installed security manager
  a class name | the named class | Success or throws `SecurityException` if not permitted by the currently installed security manager

  A future release of the JDK may change the default value of the `java.security.manager` system property to "`disallow`".

  The current security manager is returned by the `getSecurityManager` method.

  The special method `checkPermission(java.security.Permission)` determines whether an access request indicated by a specified permission should be granted or denied. The default implementation calls

         AccessController.checkPermission(perm);

  If a requested access is allowed, `checkPermission` returns quietly. If denied, a `SecurityException` is thrown.

  The default implementation of each of the other `check` methods in `SecurityManager` is to call the `SecurityManager checkPermission` method to determine if the calling thread has permission to perform the requested operation.

  Note that the `checkPermission` method with just a single permission argument always performs security checks within the context of the currently executing thread. Sometimes a security check that should be made within a given context will actually need to be done from within a different context (for example, from within a worker thread). The `getSecurityContext` method and the `checkPermission` method that includes a context argument are provided for this situation. The `getSecurityContext` method returns a "snapshot" of the current calling context. (The default implementation returns an AccessControlContext object.) A sample call is the following:

         Object context = null;
         SecurityManager sm = System.getSecurityManager();
         if (sm != null) context = sm.getSecurityContext();

  The `checkPermission` method that takes a context object in addition to a permission makes access decisions based on that context, rather than on that of the current execution thread. Code within a different context can thus call that method, passing the permission and the previously-saved context object. A sample call, using the SecurityManager `sm` obtained as in the previous example, is the following:

         if (sm != null) sm.checkPermission(permission, context);

  Permissions fall into these categories: File, Socket, Net, Security, Runtime, Property, AWT, Reflect, and Serializable. The classes managing these various permission categories are `java.io.FilePermission`, `java.net.SocketPermission`, `java.net.NetPermission`, `java.security.SecurityPermission`, `java.lang.RuntimePermission`, `java.util.PropertyPermission`, `java.awt.AWTPermission`, `java.lang.reflect.ReflectPermission`, and `java.io.SerializablePermission`.

  All but the first two (FilePermission and SocketPermission) are subclasses of `java.security.BasicPermission`, which itself is an abstract subclass of the top-level class for permissions, which is `java.security.Permission`. BasicPermission defines the functionality needed for all permissions that contain a name that follows the hierarchical property naming convention (for example, "exitVM", "setFactory", "queuePrintJob", etc). An asterisk may appear at the end of the name, following a ".", or by itself, to signify a wildcard match. For example: "a.*" or "*" is valid, "*a" or "a*b" is not valid.

  FilePermission and SocketPermission are subclasses of the top-level class for permissions (`java.security.Permission`). Classes like these that have a more complicated name syntax than that used by BasicPermission subclass directly from Permission rather than from BasicPermission. For example, for a `java.io.FilePermission` object, the permission name is the path name of a file (or directory).

  Some of the permission classes have an "actions" list that tells the actions that are permitted for the object. For example, for a `java.io.FilePermission` object, the actions list (such as "read, write") specifies which actions are granted for the specified file (or for files in the specified directory).

  Other permission classes are for "named" permissions - ones that contain a name but no actions list; you either have the named permission or you don't.

  Note: There is also a `java.security.AllPermission` permission that implies all permissions. It exists to simplify the work of system administrators who might need to perform multiple tasks that require all (or numerous) permissions.

  See Permissions in the Java Development Kit (JDK) for permission-related information. This document includes a table listing the various SecurityManager `check` methods and the permission(s) the default implementation of each such method requires. It also contains a table of the methods that require permissions, and for each such method tells which permission it requires.

  Since:
    1.0
  See Also:
    `ClassLoader`, `SecurityException`, `getSecurityManager`, `setSecurityManager`, `AccessController`, `AccessControlContext`, `AccessControlException`, `Permission`, `BasicPermission`, `FilePermission`, `SocketPermission`, `PropertyPermission`, `RuntimePermission`, `Policy`, `SecurityPermission`, `ProtectionDomain`

- - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `SecurityManager()` | Constructs a new `SecurityManager`.

  - ### Method Summary

    Modifier and Type | Method | Description
    --- | --- | ---
    `void` | `checkAccept​(String host, int port)` | Throws a `SecurityException` if the calling thread is not permitted to accept a socket connection from the specified host and port number.
    `void` | `checkAccess​(Thread t)` | Throws a `SecurityException` if the calling thread is not allowed to modify the thread argument.
    `void` | `checkAccess​(ThreadGroup g)` | Throws a `SecurityException` if the calling thread is not allowed to modify the thread group argument.
    `void` | `checkConnect​(String host, int port)` | Throws a `SecurityException` if the calling thread is not allowed to open a socket connection to the specified host and port number.
    `void` | `checkConnect​(String host, int port, Object context)` | Throws a `SecurityException` if the specified security context is not allowed to open a socket connection to the specified host and port number.
    `void` | `checkCreateClassLoader()` | Throws a `SecurityException` if the calling thread is not allowed to create a new class loader.
    `void` | `checkDelete​(String file)` | Throws a `SecurityException` if the calling thread is not allowed to delete the specified file.
    `void` | `checkExec​(String cmd)` | Throws a `SecurityException` if the calling thread is not allowed to create a subprocess.
    `void` | `checkExit​(int status)` | Throws a `SecurityException` if the calling thread is not allowed to cause the Java Virtual Machine to halt with the specified status code.
    `void` | `checkLink​(String lib)` | Throws a `SecurityException` if the calling thread is not allowed to dynamic link the library code specified by the string argument file.
    `void` | `checkListen​(int port)` | Throws a `SecurityException` if the calling thread is not allowed to wait for a connection request on the specified local port number.
    `void` | `checkMulticast​(InetAddress maddr)` | Throws a `SecurityException` if the calling thread is not allowed to use (join/leave/send/receive) IP multicast.
    `void` | `checkMulticast​(InetAddress maddr, byte ttl)` | Deprecated. Use #checkPermission(java.security.Permission) instead
    `void` | `checkPackageAccess​(String pkg)` | Throws a `SecurityException` if the calling thread is not allowed to access the specified package.
    `void` | `checkPackageDefinition​(String pkg)` | Throws a `SecurityException` if the calling thread is not allowed to define classes in the specified package.
    `void` | `checkPermission​(Permission perm)` | Throws a `SecurityException` if the requested access, specified by the given permission, is not permitted based on the security policy currently in effect.
    `void` | `checkPermission​(Permission perm, Object context)` | Throws a `SecurityException` if the specified security context is denied access to the resource specified by the given permission.
    `void` | `checkPrintJobAccess()` | Throws a `SecurityException` if the calling thread is not allowed to initiate a print job request.
    `void` | `checkPropertiesAccess()` | Throws a `SecurityException` if the calling thread is not allowed to access or modify the system properties.
    `void` | `checkPropertyAccess​(String key)` | Throws a `SecurityException` if the calling thread is not allowed to access the system property with the specified `key` name.
    `void` | `checkRead​(FileDescriptor fd)` | Throws a `SecurityException` if the calling thread is not allowed to read from the specified file descriptor.
    `void` | `checkRead​(String file)` | Throws a `SecurityException` if the calling thread is not allowed to read the file specified by the string argument.
    `void` | `checkRead​(String file, Object context)` | Throws a `SecurityException` if the specified security context is not allowed to read the file specified by the string argument.
    `void` | `checkSecurityAccess​(String target)` | Determines whether the permission with the specified permission target name should be granted or denied.
    `void` | `checkSetFactory()` | Throws a `SecurityException` if the calling thread is not allowed to set the socket factory used by `ServerSocket` or `Socket`, or the stream handler factory used by `URL`.
    `void` | `checkWrite​(FileDescriptor fd)` | Throws a `SecurityException` if the calling thread is not allowed to write to the specified file descriptor.
    `void` | `checkWrite​(String file)` | Throws a `SecurityException` if the calling thread is not allowed to write to the file specified by the string argument.
    `protected Class<?>[]` | `getClassContext()` | Returns the current execution stack as an array of classes.
    `Object` | `getSecurityContext()` | Creates an object that encapsulates the current execution environment.
    `ThreadGroup` | `getThreadGroup()` | Returns the thread group into which to instantiate any new thread being created at the time this is being called.

    - ### Methods declared in class java.lang.Object

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

- - ### Constructor Detail

    - #### SecurityManager

          public SecurityManager()

      Constructs a new `SecurityManager`.

      If there is a security manager already installed, this method first calls the security manager's `checkPermission` method with the `RuntimePermission("createSecurityManager")` permission to ensure the calling thread has permission to create a new security manager. This may result in throwing a `SecurityException`.

      Throws:
        `SecurityException` - if a security manager already exists and its `checkPermission` method doesn't allow creation of a new security manager.
      See Also:
        `System.getSecurityManager()`, `checkPermission`, `RuntimePermission`

  - ### Method Detail

    - #### getClassContext

          protected Class<?>[] getClassContext()

      Returns the current execution stack as an array of classes.

      The length of the array is the number of methods on the execution stack. The element at index `0` is the class of the currently executing method, the element at index `1` is the class of that method's caller, and so on.

      Returns:
        the execution stack.

    - #### getSecurityContext

          public Object getSecurityContext()

      Creates an object that encapsulates the current execution environment. The result of this method is used, for example, by the three-argument `checkConnect` method and by the two-argument `checkRead` method. These methods are needed because a trusted method may be called on to read a file or open a socket on behalf of another method. The trusted method needs to determine if the other (possibly untrusted) method would be allowed to perform the operation on its own.

      The default implementation of this method is to return an `AccessControlContext` object.

      Returns:
        an implementation-dependent object that encapsulates sufficient information about the current execution environment to perform some security checks later.
      See Also:
        `checkConnect`, `checkRead`, `AccessControlContext`

    - #### checkPermission

          public void checkPermission​(Permission perm)

      Throws a `SecurityException` if the requested access, specified by the given permission, is not permitted based on the security policy currently in effect.

      This method calls `AccessController.checkPermission` with the given permission.

      Parameters:
        `perm` - the requested permission.
      Throws:
        `SecurityException` - if access is not permitted based on the current security policy.
        `NullPointerException` - if the permission argument is `null`.
      Since:
        1.2

    - #### checkPermission

          public void checkPermission​(Permission perm,
                                      Object context)

      Throws a `SecurityException` if the specified security context is denied access to the resource specified by the given permission. The context must be a security context returned by a previous call to `getSecurityContext` and the access control decision is based upon the configured security policy for that security context.

      If `context` is an instance of `AccessControlContext` then the `AccessControlContext.checkPermission` method is invoked with the specified permission.

      If `context` is not an instance of `AccessControlContext` then a `SecurityException` is thrown.

      Parameters:
        `perm` - the specified permission
        `context` - a system-dependent security context.
      Throws:
        `SecurityException` - if the specified security context is not an instance of `AccessControlContext` (e.g., is `null`), or is denied access to the resource specified by the given permission.
        `NullPointerException` - if the permission argument is `null`.
      Since:
        1.2
      See Also:
        `getSecurityContext()`, `AccessControlContext.checkPermission(java.security.Permission)`

    - #### checkCreateClassLoader

          public void checkCreateClassLoader()

      Throws a `SecurityException` if the calling thread is not allowed to create a new class loader.

      This method calls `checkPermission` with the `RuntimePermission("createClassLoader")` permission.

      If you override this method, then you should make a call to `super.checkCreateClassLoader` at the point the overridden method would normally throw an exception.

      Throws:
        `SecurityException` - if the calling thread does not have permission to create a new class loader.
      See Also:
        `ClassLoader()`, `checkPermission`

    - #### checkAccess

          public void checkAccess​(Thread t)

      Throws a `SecurityException` if the calling thread is not allowed to modify the thread argument.

      This method is invoked for the current security manager by the `stop`, `suspend`, `resume`, `setPriority`, `setName`, and `setDaemon` methods of class `Thread`.

      If the thread argument is a system thread (belongs to the thread group with a `null` parent) then this method calls `checkPermission` with the `RuntimePermission("modifyThread")` permission. If the thread argument is not a system thread, this method just returns silently.

      Applications that want a stricter policy should override this method. If this method is overridden, the method that overrides it should additionally check to see if the calling thread has the `RuntimePermission("modifyThread")` permission, and if so, return silently. This is to ensure that code granted that permission (such as the JDK itself) is allowed to manipulate any thread.

      If this method is overridden, then `super.checkAccess` should be called by the first statement in the overridden method, or the equivalent security check should be placed in the overridden method.

      Parameters:
        `t` - the thread to be checked.
      Throws:
        `SecurityException` - if the calling thread does not have permission to modify the thread.
        `NullPointerException` - if the thread argument is `null`.
      See Also:
        `resume`, `setDaemon`, `setName`, `setPriority`, `stop`, `suspend`, `checkPermission`

    - #### checkAccess

          public void checkAccess​(ThreadGroup g)

      Throws a `SecurityException` if the calling thread is not allowed to modify the thread group argument.

      This method is invoked for the current security manager when a new child thread or child thread group is created, and by the `setDaemon`, `setMaxPriority`, `stop`, `suspend`, `resume`, and `destroy` methods of class `ThreadGroup`.

      If the thread group argument is the system thread group ( has a `null` parent) then this method calls `checkPermission` with the `RuntimePermission("modifyThreadGroup")` permission. If the thread group argument is not the system thread group, this method just returns silently.

      Applications that want a stricter policy should override this method. If this method is overridden, the method that overrides it should additionally check to see if the calling thread has the `RuntimePermission("modifyThreadGroup")` permission, and if so, return silently. This is to ensure that code granted that permission (such as the JDK itself) is allowed to manipulate any thread.

      If this method is overridden, then `super.checkAccess` should be called by the first statement in the overridden method, or the equivalent security check should be placed in the overridden method.

      Parameters:
        `g` - the thread group to be checked.
      Throws:
        `SecurityException` - if the calling thread does not have permission to modify the thread group.
        `NullPointerException` - if the thread group argument is `null`.
      See Also:
        `destroy`, `resume`, `setDaemon`, `setMaxPriority`, `stop`, `suspend`, `checkPermission`

    - #### checkExit

          public void checkExit​(int status)

      Throws a `SecurityException` if the calling thread is not allowed to cause the Java Virtual Machine to halt with the specified status code.

      This method is invoked for the current security manager by the `exit` method of class `Runtime`. A status of `0` indicates success; other values indicate various errors.

      This method calls `checkPermission` with the `RuntimePermission("exitVM."+status)` permission.

      If you override this method, then you should make a call to `super.checkExit` at the point the overridden method would normally throw an exception.

      Parameters:
        `status` - the exit status.
      Throws:
        `SecurityException` - if the calling thread does not have permission to halt the Java Virtual Machine with the specified status.
      See Also:
        `exit`, `checkPermission`

    - #### checkExec

          public void checkExec​(String cmd)

      Throws a `SecurityException` if the calling thread is not allowed to create a subprocess.

      This method is invoked for the current security manager by the `exec` methods of class `Runtime`.

      This method calls `checkPermission` with the `FilePermission(cmd,"execute")` permission if cmd is an absolute path, otherwise it calls `checkPermission` with `FilePermission("<<ALL FILES>>","execute")`.

      If you override this method, then you should make a call to `super.checkExec` at the point the overridden method would normally throw an exception.

      Parameters:
        `cmd` - the specified system command.
      Throws:
        `SecurityException` - if the calling thread does not have permission to create a subprocess.
        `NullPointerException` - if the `cmd` argument is `null`.
      See Also:
        `Runtime.exec(java.lang.String)`, `Runtime.exec(java.lang.String, java.lang.String[])`, `Runtime.exec(java.lang.String[])`, `Runtime.exec(java.lang.String[], java.lang.String[])`, `checkPermission`

    - #### checkLink

          public void checkLink​(String lib)

      Throws a `SecurityException` if the calling thread is not allowed to dynamic link the library code specified by the string argument file. The argument is either a simple library name or a complete filename.

      This method is invoked for the current security manager by methods `load` and `loadLibrary` of class `Runtime`.

      This method calls `checkPermission` with the `RuntimePermission("loadLibrary."+lib)` permission.

      If you override this method, then you should make a call to `super.checkLink` at the point the overridden method would normally throw an exception.

      Parameters:
        `lib` - the name of the library.
      Throws:
        `SecurityException` - if the calling thread does not have permission to dynamically link the library.
        `NullPointerException` - if the `lib` argument is `null`.
      See Also:
        `Runtime.load(java.lang.String)`, `Runtime.loadLibrary(java.lang.String)`, `checkPermission`

    - #### checkRead

          public void checkRead​(FileDescriptor fd)

      Throws a `SecurityException` if the calling thread is not allowed to read from the specified file descriptor.

      This method calls `checkPermission` with the `RuntimePermission("readFileDescriptor")` permission.

      If you override this method, then you should make a call to `super.checkRead` at the point the overridden method would normally throw an exception.

      Parameters:
        `fd` - the system-dependent file descriptor.
      Throws:
        `SecurityException` - if the calling thread does not have permission to access the specified file descriptor.
        `NullPointerException` - if the file descriptor argument is `null`.
      See Also:
        `FileDescriptor`, `checkPermission`

    - #### checkRead

          public void checkRead​(String file)

      Throws a `SecurityException` if the calling thread is not allowed to read the file specified by the string argument.

      This method calls `checkPermission` with the `FilePermission(file,"read")` permission.

      If you override this method, then you should make a call to `super.checkRead` at the point the overridden method would normally throw an exception.

      Parameters:
        `file` - the system-dependent file name.
      Throws:
        `SecurityException` - if the calling thread does not have permission to access the specified file.
        `NullPointerException` - if the `file` argument is `null`.
      See Also:
        `checkPermission`

    - #### checkRead

          public void checkRead​(String file,
                                Object context)

      Throws a `SecurityException` if the specified security context is not allowed to read the file specified by the string argument. The context must be a security context returned by a previous call to `getSecurityContext`.

      If `context` is an instance of `AccessControlContext` then the `AccessControlContext.checkPermission` method will be invoked with the `FilePermission(file,"read")` permission.

      If `context` is not an instance of `AccessControlContext` then a `SecurityException` is thrown.

      If you override this method, then you should make a call to `super.checkRead` at the point the overridden method would normally throw an exception.

      Parameters:
        `file` - the system-dependent filename.
        `context` - a system-dependent security context.
      Throws:
        `SecurityException` - if the specified security context is not an instance of `AccessControlContext` (e.g., is `null`), or does not have permission to read the specified file.
        `NullPointerException` - if the `file` argument is `null`.
      See Also:
        `getSecurityContext()`, `AccessControlContext.checkPermission(java.security.Permission)`

    - #### checkWrite

          public void checkWrite​(FileDescriptor fd)

      Throws a `SecurityException` if the calling thread is not allowed to write to the specified file descriptor.

      This method calls `checkPermission` with the `RuntimePermission("writeFileDescriptor")` permission.

      If you override this method, then you should make a call to `super.checkWrite` at the point the overridden method would normally throw an exception.

      Parameters:
        `fd` - the system-dependent file descriptor.
      Throws:
        `SecurityException` - if the calling thread does not have permission to access the specified file descriptor.
        `NullPointerException` - if the file descriptor argument is `null`.
      See Also:
        `FileDescriptor`, `checkPermission`

    - #### checkWrite

          public void checkWrite​(String file)

      Throws a `SecurityException` if the calling thread is not allowed to write to the file specified by the string argument.

      This method calls `checkPermission` with the `FilePermission(file,"write")` permission.

      If you override this method, then you should make a call to `super.checkWrite` at the point the overridden method would normally throw an exception.

      Parameters:
        `file` - the system-dependent filename.
      Throws:
        `SecurityException` - if the calling thread does not have permission to access the specified file.
        `NullPointerException` - if the `file` argument is `null`.
      See Also:
        `checkPermission`

    - #### checkDelete

          public void checkDelete​(String file)

      Throws a `SecurityException` if the calling thread is not allowed to delete the specified file.

      This method is invoked for the current security manager by the `delete` method of class `File`.

      This method calls `checkPermission` with the `FilePermission(file,"delete")` permission.

      If you override this method, then you should make a call to `super.checkDelete` at the point the overridden method would normally throw an exception.

      Parameters:
        `file` - the system-dependent filename.
      Throws:
        `SecurityException` - if the calling thread does not have permission to delete the file.
        `NullPointerException` - if the `file` argument is `null`.
      See Also:
        `File.delete()`, `checkPermission`

    - #### checkConnect

          public void checkConnect​(String host,
                                   int port)

      Throws a `SecurityException` if the calling thread is not allowed to open a socket connection to the specified host and port number.

      A port number of `-1` indicates that the calling method is attempting to determine the IP address of the specified host name.

      This method calls `checkPermission` with the `SocketPermission(host+":"+port,"connect")` permission if the port is not equal to -1. If the port is equal to -1, then it calls `checkPermission` with the `SocketPermission(host,"resolve")` permission.

      If you override this method, then you should make a call to `super.checkConnect` at the point the overridden method would normally throw an exception.

      Parameters:
        `host` - the host name port to connect to.
        `port` - the protocol port to connect to.
      Throws:
        `SecurityException` - if the calling thread does not have permission to open a socket connection to the specified `host` and `port`.
        `NullPointerException` - if the `host` argument is `null`.
      See Also:
        `checkPermission`

    - #### checkConnect

          public void checkConnect​(String host,
                                   int port,
                                   Object context)

      Throws a `SecurityException` if the specified security context is not allowed to open a socket connection to the specified host and port number.

      A port number of `-1` indicates that the calling method is attempting to determine the IP address of the specified host name.

      If `context` is not an instance of `AccessControlContext` then a `SecurityException` is thrown.

      Otherwise, the port number is checked. If it is not equal to -1, the `context`'s `checkPermission` method is called with a `SocketPermission(host+":"+port,"connect")` permission. If the port is equal to -1, then the `context`'s `checkPermission` method is called with a `SocketPermission(host,"resolve")` permission.

      If you override this method, then you should make a call to `super.checkConnect` at the point the overridden method would normally throw an exception.

      Parameters:
        `host` - the host name port to connect to.
        `port` - the protocol port to connect to.
        `context` - a system-dependent security context.
      Throws:
        `SecurityException` - if the specified security context is not an instance of `AccessControlContext` (e.g., is `null`), or does not have permission to open a socket connection to the specified `host` and `port`.
        `NullPointerException` - if the `host` argument is `null`.
      See Also:
        `getSecurityContext()`, `AccessControlContext.checkPermission(java.security.Permission)`

    - #### checkListen

          public void checkListen​(int port)

      Throws a `SecurityException` if the calling thread is not allowed to wait for a connection request on the specified local port number.

      This method calls `checkPermission` with the `SocketPermission("localhost:"+port,"listen")`.

      If you override this method, then you should make a call to `super.checkListen` at the point the overridden method would normally throw an exception.

      Parameters:
        `port` - the local port.
      Throws:
        `SecurityException` - if the calling thread does not have permission to listen on the specified port.
      See Also:
        `checkPermission`

    - #### checkAccept

          public void checkAccept​(String host,
                                  int port)

      Throws a `SecurityException` if the calling thread is not permitted to accept a socket connection from the specified host and port number.

      This method is invoked for the current security manager by the `accept` method of class `ServerSocket`.

      This method calls `checkPermission` with the `SocketPermission(host+":"+port,"accept")` permission.

      If you override this method, then you should make a call to `super.checkAccept` at the point the overridden method would normally throw an exception.

      Parameters:
        `host` - the host name of the socket connection.
        `port` - the port number of the socket connection.
      Throws:
        `SecurityException` - if the calling thread does not have permission to accept the connection.
        `NullPointerException` - if the `host` argument is `null`.
      See Also:
        `ServerSocket.accept()`, `checkPermission`

    - #### checkMulticast

          public void checkMulticast​(InetAddress maddr)

      Throws a `SecurityException` if the calling thread is not allowed to use (join/leave/send/receive) IP multicast.

      This method calls `checkPermission` with the `java.net.SocketPermission(maddr.getHostAddress(), "accept,connect")` permission.

      If you override this method, then you should make a call to `super.checkMulticast` at the point the overridden method would normally throw an exception.

      Parameters:
        `maddr` - Internet group address to be used.
      Throws:
        `SecurityException` - if the calling thread is not allowed to use (join/leave/send/receive) IP multicast.
        `NullPointerException` - if the address argument is `null`.
      Since:
        1.1
      See Also:
        `checkPermission`

    - #### checkMulticast

          @Deprecated(since="1.4")
          public void checkMulticast​(InetAddress maddr,
                                     byte ttl)

      Deprecated.
      Use #checkPermission(java.security.Permission) instead
      Throws a `SecurityException` if the calling thread is not allowed to use (join/leave/send/receive) IP multicast.

      This method calls `checkPermission` with the `java.net.SocketPermission(maddr.getHostAddress(), "accept,connect")` permission.

      If you override this method, then you should make a call to `super.checkMulticast` at the point the overridden method would normally throw an exception.

      Parameters:
        `maddr` - Internet group address to be used.
        `ttl` - value in use, if it is multicast send. Note: this particular implementation does not use the ttl parameter.
      Throws:
        `SecurityException` - if the calling thread is not allowed to use (join/leave/send/receive) IP multicast.
        `NullPointerException` - if the address argument is `null`.
      Since:
        1.1
      See Also:
        `checkPermission`

    - #### checkPropertiesAccess

          public void checkPropertiesAccess()

      Throws a `SecurityException` if the calling thread is not allowed to access or modify the system properties.

      This method is used by the `getProperties` and `setProperties` methods of class `System`.

      This method calls `checkPermission` with the `PropertyPermission("*", "read,write")` permission.

      If you override this method, then you should make a call to `super.checkPropertiesAccess` at the point the overridden method would normally throw an exception.

      Throws:
        `SecurityException` - if the calling thread does not have permission to access or modify the system properties.
      See Also:
        `System.getProperties()`, `System.setProperties(java.util.Properties)`, `checkPermission`

    - #### checkPropertyAccess

          public void checkPropertyAccess​(String key)

      Throws a `SecurityException` if the calling thread is not allowed to access the system property with the specified `key` name.

      This method is used by the `getProperty` method of class `System`.

      This method calls `checkPermission` with the `PropertyPermission(key, "read")` permission.

      If you override this method, then you should make a call to `super.checkPropertyAccess` at the point the overridden method would normally throw an exception.

      Parameters:
        `key` - a system property key.
      Throws:
        `SecurityException` - if the calling thread does not have permission to access the specified system property.
        `NullPointerException` - if the `key` argument is `null`.
        `IllegalArgumentException` - if `key` is empty.
      See Also:
        `System.getProperty(java.lang.String)`, `checkPermission`

    - #### checkPrintJobAccess

          public void checkPrintJobAccess()

      Throws a `SecurityException` if the calling thread is not allowed to initiate a print job request.

      This method calls `checkPermission` with the `RuntimePermission("queuePrintJob")` permission.

      If you override this method, then you should make a call to `super.checkPrintJobAccess` at the point the overridden method would normally throw an exception.

      Throws:
        `SecurityException` - if the calling thread does not have permission to initiate a print job request.
      Since:
        1.1
      See Also:
        `checkPermission`

    - #### checkPackageAccess

          public void checkPackageAccess​(String pkg)

      Throws a `SecurityException` if the calling thread is not allowed to access the specified package.

      During class loading, this method may be called by the `loadClass` method of class loaders and by the Java Virtual Machine to ensure that the caller is allowed to access the package of the class that is being loaded.

      This method checks if the specified package starts with or equals any of the packages in the `package.access` Security Property. An implementation may also check the package against an additional list of restricted packages as noted below. If the package is restricted, `checkPermission(Permission)` is called with a `RuntimePermission("accessClassInPackage."+pkg)` permission.

      If this method is overridden, then `super.checkPackageAccess` should be called as the first line in the overridden method.

      Implementation Note:
        This implementation also restricts all non-exported packages of modules loaded by the platform class loader or its ancestors. A "non-exported package" refers to a package that is not exported to all modules. Specifically, it refers to a package that either is not exported at all by its containing module or is exported in a qualified fashion by its containing module.
      Parameters:
        `pkg` - the package name.
      Throws:
        `SecurityException` - if the calling thread does not have permission to access the specified package.
        `NullPointerException` - if the package name argument is `null`.
      See Also:
        `loadClass`, `getProperty`, `checkPermission`

    - #### checkPackageDefinition

          public void checkPackageDefinition​(String pkg)

      Throws a `SecurityException` if the calling thread is not allowed to define classes in the specified package.

      This method is called by the `loadClass` method of some class loaders.

      This method checks if the specified package starts with or equals any of the packages in the `package.definition` Security Property. An implementation may also check the package against an additional list of restricted packages as noted below. If the package is restricted, `checkPermission(Permission)` is called with a `RuntimePermission("defineClassInPackage."+pkg)` permission.

      If this method is overridden, then `super.checkPackageDefinition` should be called as the first line in the overridden method.

      Implementation Note:
        This implementation also restricts all non-exported packages of modules loaded by the platform class loader or its ancestors. A "non-exported package" refers to a package that is not exported to all modules. Specifically, it refers to a package that either is not exported at all by its containing module or is exported in a qualified fashion by its containing module.
      Parameters:
        `pkg` - the package name.
      Throws:
        `SecurityException` - if the calling thread does not have permission to define classes in the specified package.
        `NullPointerException` - if the package name argument is `null`.
      See Also:
        `ClassLoader.loadClass(String, boolean)`, `getProperty`, `checkPermission`

    - #### checkSetFactory

          public void checkSetFactory()

      Throws a `SecurityException` if the calling thread is not allowed to set the socket factory used by `ServerSocket` or `Socket`, or the stream handler factory used by `URL`.

      This method calls `checkPermission` with the `RuntimePermission("setFactory")` permission.

      If you override this method, then you should make a call to `super.checkSetFactory` at the point the overridden method would normally throw an exception.

      Throws:
        `SecurityException` - if the calling thread does not have permission to specify a socket factory or a stream handler factory.
      See Also:
        `setSocketFactory`, `setSocketImplFactory`, `setURLStreamHandlerFactory`, `checkPermission`

    - #### checkSecurityAccess

          public void checkSecurityAccess​(String target)

      Determines whether the permission with the specified permission target name should be granted or denied.

      If the requested permission is allowed, this method returns quietly. If denied, a SecurityException is raised.

      This method creates a `SecurityPermission` object for the given permission target name and calls `checkPermission` with it.

      See the documentation for ``SecurityPermission`` for a list of possible permission target names.

      If you override this method, then you should make a call to `super.checkSecurityAccess` at the point the overridden method would normally throw an exception.

      Parameters:
        `target` - the target name of the `SecurityPermission`.
      Throws:
        `SecurityException` - if the calling thread does not have permission for the requested access.
        `NullPointerException` - if `target` is null.
        `IllegalArgumentException` - if `target` is empty.
      Since:
        1.1
      See Also:
        `checkPermission`

    - #### getThreadGroup

          public ThreadGroup getThreadGroup()

      Returns the thread group into which to instantiate any new thread being created at the time this is being called. By default, it returns the thread group of the current thread. This should be overridden by a specific security manager to return the appropriate thread group.
      Returns:
        ThreadGroup that new threads are instantiated into
      Since:
        1.1
      See Also:
        `ThreadGroup`