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## java.lang
Class SecurityManager

    java.lang.Object
      |
      +--java.lang.SecurityManager

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. The only exception to this convention is `checkTopLevelWindow`, which returns a `boolean` value.

The current security manager is set by the `setSecurityManager` method in class `System`. The current security manager is obtained 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.

As of Java 2 SDK v1.2, 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 pathname 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 2 SDK for permission-related information. This document includes, for example, 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 all the version 1.2 methods that require permissions, and for each such method tells which permission it requires.

For more information about `SecurityManager` changes made in the Java 2 SDK and advice regarding porting of 1.1-style security managers, see the security documentation.

Since:
  JDK1.0
See Also:
  `ClassLoader`, `SecurityException`, `checkTopLevelWindow`, `getSecurityManager`, `setSecurityManager`, `AccessController`, `AccessControlContext`, `AccessControlException`, `Permission`, `BasicPermission`, `FilePermission`, `SocketPermission`, `PropertyPermission`, `RuntimePermission`, `java.awt.AWTPermission`, `Policy`, `SecurityPermission`, `ProtectionDomain`

Constructor Summary
`SecurityManager()` Constructs a new `SecurityManager`.

Method Summary
`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` | `checkAwtEventQueueAccess()` Throws a `SecurityException` if the calling thread is not allowed to access the AWT event queue, or the AWT package is not available.
`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` | `checkMemberAccess(Class clazz, int which)` Throws a `SecurityException` if the calling thread is not allowed to access members.
`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)` Throws a `SecurityException` if the calling thread is not allowed to use (join/leave/send/receive) IP multicast.
`void` | `checkPackageAccess(String pkg)` Throws a `SecurityException` if the calling thread is not allowed to access the package specified by the argument.
`void` | `checkPackageDefinition(String pkg)` Throws a `SecurityException` if the calling thread is not allowed to define classes in the package specified by the argument.
`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` | `checkSystemClipboardAccess()` Throws a `SecurityException` if the calling thread is not allowed to access the system clipboard, or the AWT package is not available.
`boolean` | `checkTopLevelWindow(Object window)` Returns `false` if the calling thread is not trusted to bring up the top-level window indicated by the `window` argument, or the AWT package is not available.
`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 inherited from 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.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 SDK 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:
    `setDaemon`, `setName`, `setPriority`, `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 SDK 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`, `setDaemon`, `setMaxPriority`, `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")` 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.

  If port is not 0, this method calls `checkPermission` with the `SocketPermission("localhost:"+port,"listen")`. If port is zero, this method calls `checkPermission` with `SocketPermission("localhost:1024-","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:
    JDK1.1
  See Also:
    `checkPermission`

### checkMulticast

    public void checkMulticast(InetAddress maddr,
                               byte ttl)

  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:
    JDK1.1
  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`

### checkTopLevelWindow

    public boolean checkTopLevelWindow(Object window)

  Returns `false` if the calling thread is not trusted to bring up the top-level window indicated by the `window` argument, or the AWT package is not available. FIXME - would it be better to throw an exception if AWT is not found? In this case, the caller can still decide to show the window, but the window should include some sort of visual warning. If the method returns `true`, then the window can be shown without any special restrictions.

  See class `Window` for more information on trusted and untrusted windows.

  This method calls `checkPermission` with the `AWTPermission("showWindowWithoutWarningBanner")` permission, and returns `true` if a SecurityException is not thrown, otherwise it returns `false`.

  If you override this method, then you should make a call to `super.checkTopLevelWindow` at the point the overridden method would normally return `false`, and the value of `super.checkTopLevelWindow` should be returned.

  Parameters:
    `window` - the new window that is being created.
  Returns:
    `true` if the calling thread is trusted to put up top-level windows; `false` otherwise.
  Throws:
    `SecurityException` - if creation is disallowed entirely.
    `NullPointerException` - if the `window` argument is `null`.
  See Also:
    `java.awt.Window`, `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:
    JDK1.1
  See Also:
    `checkPermission`

### checkSystemClipboardAccess

    public void checkSystemClipboardAccess()

  Throws a `SecurityException` if the calling thread is not allowed to access the system clipboard, or the AWT package is not available.

  This method calls `checkPermission` with the `AWTPermission("accessClipboard")` permission.

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

  Throws:
    `SecurityException` - if the calling thread does not have permission to access the system clipboard.
  Since:
    JDK1.1
  See Also:
    `checkPermission`

### checkAwtEventQueueAccess

    public void checkAwtEventQueueAccess()

  Throws a `SecurityException` if the calling thread is not allowed to access the AWT event queue, or the AWT package is not available.

  This method calls `checkPermission` with the `AWTPermission("accessEventQueue")` permission.

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

  Throws:
    `SecurityException` - if the calling thread does not have permission to access the AWT event queue.
  Since:
    JDK1.1
  See Also:
    `checkPermission`

### checkPackageAccess

    public void checkPackageAccess(String pkg)

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

  This method is used by the `loadClass` method of class loaders.

  This method first gets a list of restricted packages by obtaining a comma-separated list from a call to `java.security.Security.getProperty("package.access")`, and checks to see if `pkg` starts with or equals any of the restricted packages. If it does, then `checkPermission` gets called with the `RuntimePermission("accessClassInPackage."+pkg)` permission.

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

  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 package specified by the argument.

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

  This method first gets a list of restricted packages by obtaining a comma-separated list from a call to `java.security.Security.getProperty("package.definition")`, and checks to see if `pkg` starts with or equals any of the restricted packages. If it does, then `checkPermission` gets called with the `RuntimePermission("defineClassInPackage."+pkg)` permission.

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

  Parameters:
    `pkg` - the package name.
  Throws:
    `SecurityException` - if the calling thread does not have permission to define classes in the specified package.
  See Also:
    `ClassLoader.loadClass(java.lang.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`

### checkMemberAccess

    public void checkMemberAccess(Class clazz,
                                  int which)

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

  The default policy is to allow access to PUBLIC members, as well as access to classes that have the same class loader as the caller. In all other cases, this method calls `checkPermission` with the `RuntimePermission("accessDeclaredMembers")` permission.

  If this method is overridden, then a call to `super.checkMemberAccess` cannot be made, as the default implementation of `checkMemberAccess` relies on the code being checked being at a stack depth of 4.

  Parameters:
    `clazz` - the class that reflection is to be performed on.
    `which` - type of access, PUBLIC or DECLARED.
  Throws:
    `SecurityException` - if the caller does not have permission to access members.
    `NullPointerException` - if the `clazz` argument is `null`.
  Since:
    JDK1.1
  See Also:
    `Member`, `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:
    JDK1.1
  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:
    JDK1.1
  See Also:
    `ThreadGroup`

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