[Chapter 12] SecurityManager

#

| Chapter 12 The java.lang Package |

# SecurityManager

## Name

SecurityManager

## Synopsis

Class Name:

  `java.lang.SecurityManager`

Superclass:

  `java.lang.Object`

Immediate Subclasses:

  None

Interfaces Implemented:

  None

Availability:

  JDK 1.0 or later

## Description

The `SecurityManager` class provides a way of implementing a comprehensive security policy for a Java program. As of this writing, `SecurityManager` objects are used primarily by Web browsers to establish security policies for applets. However, the use of a `SecurityManager` object is appropriate in any situation where a hosting environment wants to limit the actions of hosted programs.

The `SecurityManager` class contains methods that are called by methods in other classes to ask for permission to do something that can affect the security of the system. These permission methods all have names that begin with `check`. If a `check` method does not permit an action, it throws a `SecurityException` or returns a value that indicates the lack of permission. The `SecurityManager` class provides default implementations of all of the `check` methods. These default implementations are the most restrictive possible implementations; they simply deny permission to do anything that can affect the security of the system.

The `SecurityManager` class is an `abstract` class. A hosting environment should define a subclass of `SecurityManager` that implements an appropriate security policy. To give the subclass of `SecurityManager` control over security, the hosting environment creates an instance of the class and installs it by passing it to the `setSecurityManager()` method of the `System` class. Once a `SecurityManager` object is installed, it cannot be changed. If the `setSecurityManager()` method is called any additional times, it throws a `SecurityException`.

The methods in other classes that want to ask the `SecurityManager` for permission to do something are able to access the `SecurityManager` object by calling the `getSecurityManager()` method of the `System` class. This method returns the `SecurityManager` object, or `null` to indicate that there is no `SecurityManager` installed.

## Class Summary

    public abstract class java.lang.SecurityManager extends java.lang.Object {
        // Constructors
        protected SecurityManager();
        // Variables
        protected boolean inCheck;
        // Instance Methods
        public void checkAccept(String host, int port);
        public void checkAccess(Thread t);
        public void checkAccess(ThreadGroup g);
        public void checkAwtEventQueueAccess();                  // New in 1.1
        public void checkConnect(String host, int port);
        public void checkConnect(String host, int port, Object context);
        public void checkCreateClassLoader();
        public void checkDelete(String file);
        public void checkExec(String cmd);
        public void checkExit(int status);
        public void checkLink(String libname);
        public void checkListen(int port);
        public void checkMemberAccess(Class clazz, int which);   // New in 1.1
        public void checkMulticast(InetAddress maddr);           // New in 1.1
        public void checkMulticast(InetAddress maddr, byte ttl); // New in 1.1
        public void checkPackageAccess();
        public void checkPackageDefinition();
        public void checkPrintJobAccess();                       // New in 1.1
        public void checkPropertiesAccess();
        public void checkPropertyAccess(String key);
        public void checkRead(int fd);
        public void checkRead(String file);
        public void checkRead(String file, Object context);
        public void checkSecurityAccess(String action);          // New in 1.1
        public void checkSetFactory();
        public void checkSystemClipboardAccess();                // New in 1.1
        public boolean checkTopLevelWindow();
        public void checkWrite(int fd);
        public void checkWrite(String file);
        public boolean getInCheck();
        public Object getSecurityContext();
        public ThreadGroup getThreadGroup();                     // New in 1.1
        // Protected Instance Methods
        protected int classDepth(String name);
        protected int classLoaderDepth();
        protected ClassLoader currentClassLoader();
        protected Class currentLoadedClass();                    // New in 1.1
        protected Class[] getClassContext();
        protected boolean inClass(String name);
        protected boolean inClassLoader();
    }

## Variables

### inCheck

#### `protected boolean inCheck = false`

Description

  This variable indicates whether or not a security check is in progress. A subclass of `SecurityManager` should set this variable to `true` while a security check is in progress.

  This variable can be useful for security checks that require access to resources that a hosted program may not be permitted to access. For example, a security policy might be based on the contents of a permissions file. This means that the various `check` methods need to read information from a file to decide what to do. Even though a hosted program may not be allowed to read files, the `check` methods can allow such reads when `inCheck` is `true` to support this style of security policy.

## Constructors

### SecurityManager

#### `protected SecurityManager()`

Throws

  `SecurityException`

    If a `SecurityManager` object already exists. In other words, if `System.getSecurityManager()` returns a value other than `null`.

Description

  Creates a new `SecurityManager` object. This constructor cannot be called if there is already a current `SecurityManager` installed for the program.

## Public Instance Methods

### checkAccept

#### `public void checkAccept(String host, int port)`

Parameters

  `host`

    The name of the host machine.

  `port`

    A port number.

Throws

  `SecurityException`

    If the caller does not have permission to accept the connection.

Description

  This method decides whether or not to allow a connection from the given host on the given port to be accepted. An implementation of the method should throw a `SecurityException` to deny permission to accept the connection. The method is called by the `accept()` method of the `java.net.ServerSocket` class.

  The `checkAccept()` method of `SecurityManager` always throws a `SecurityException`.

### checkAccess

#### `public void checkAccess(Thread g)`

Parameters

  `g`

    A reference to a `Thread` object.

Throws

  `SecurityException`

    If the current thread does not have permission to modify the specified thread.

Description

  This method decides whether or not to allow the current thread to modify the specified `Thread`. An implementation of the method should throw a `SecurityException` to deny permission to modify the thread. Methods of the `Thread` class that call this method include `stop()`, `suspend()`, `resume()`, `setPriority()`, `setName()`, and `setDaemon()`.

  The `checkAccess()` method of `SecurityManager` always throws a `SecurityException`.

#### `public void checkAccess(ThreadGroup g)`

Parameters

  `g`

    A reference to a `ThreadGroup` object.

Throws

  `SecurityException`

    If the current thread does not have permission to modify the specified thread group.

Description

  This method decides whether or not to allow the current thread to modify the specified `ThreadGroup`. An implementation of the method should throw a `SecurityException` to deny permission to modify the thread group. Methods of the `ThreadGroup` class that call this method include `setDaemon()`, `setMaxPriority()`, `stop()`, `suspend()`, `resume()`, and `destroy()`.

  The `checkAccess()` method of `SecurityManager` always throws a `SecurityException`.

### checkAwtEventQueueAccess

#### `public void checkAwtEventQueueAccess()`

Availability

  New as of JDK 1.1

Throws

  `SecurityException`

    If the caller does not have permission to access the AWT event queue.

Description

  This method decides whether or not to allow access to the AWT event queue. An implementation of the method should throw a `SecurityException` to deny permission to access the event queue. The method is called by the `getSystemEventQueue()` method of the `java.awt.Toolkit` class.

  The `checkAwtEventQueueAccess()` method of `SecurityManager` always throws a `SecurityException`.

### checkConnect

#### `public void checkConnect(String host, int port)`

Parameters

  `host`

    The name of the host.

  `port`

    A port number. A value of `-1` indicates an attempt to determine the IP address of given hostname.

Throws

  `SecurityException`

    If the caller does not have permission to open the socket connection.

Description

  This method decides whether or not to allow a socket connection to the given host on the given port to be opened. An implementation of the method should throw a `SecurityException` to deny permission to open the connection. The method is called by the constructors of the `java.net.Socket` class, the `send()` and `receive()` methods of the `java.net.DatagramSocket` class, and the `getByName()` and `getAllByName()` methods of the `java.net.InetAddress` class.

  The `checkConnect()` method of `SecurityManager` always throws a `SecurityException`.

####

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

Parameters

  `host`

    The name of the host.

  `port`

    A port number. A value of `-1` indicates an attempt to determine the IP address of given host name.

  `context`

    A security context object returned by this object's `getSecurityContext()` method.

Throws

  `SecurityException`

    If the specified security context does not have permission to open the socket connection.

Description

  This method decides whether or not to allow a socket connection to the given host on the given port to be opened for the specified security context. An implementation of the method should throw a `SecurityException` to deny permission to open the connection.

  The `checkConnect()` method of `SecurityManager` always throws a `SecurityException`.

### checkCreateClassLoader

#### `public void checkCreateClassLoader()`

Throws

  `SecurityException`

    If the caller does not have permission to create a `ClassLoader` object.

Description

  This method decides whether or not to allow a `ClassLoader` object to be created. An implementation of the method should throw a `SecurityException` to deny permission to create a `ClassLoader`. The method is called by the constructor of the `ClassLoader` class.

  The `checkCreateClassLoader()` method of `SecurityManager` always throws a `SecurityException`.

### checkDelete

#### `public void checkDelete(String file)`

Parameters

  `file`

    The name of a file.

Throws

  `SecurityException`

    If the caller does not have permission to delete the specified file.

Description

  This method decides whether or not to allow a file to be deleted. An implementation of the method should throw a `SecurityException` to deny permission to delete the specified file. The method is called by the `delete()` method of the `java.io.File` class.

  The `checkDelete()` method of `SecurityManager` always throws a `SecurityException`.

### checkExec

#### `public void checkExec(String cmd)`

Parameters

  `cmd`

    The name of an external command.

Throws

  `SecurityException`

    If the caller does not have permission to execute the specified command.

Description

  This method decides whether or not to allow an external command to be executed. An implementation of the method should throw a `SecurityException` to deny permission to execute the specified command. The method is called by the `exec()` methods of the `Runtime` and `System` classes.

  The `checkExec()` method of `SecurityManager` always throws a `SecurityException`.

### checkExit

#### `public void checkExit(int status)`

Parameters

  `status`

    An exit status code.

Throws

  `SecurityException`

    If the caller does not have permission to exit the Java virtual machine with the given status code.

Description

  This method decides whether or not to allow the Java virtual machine to exit with the given status code. An implementation of the method should throw a `SecurityException` to deny permission to exit with the specified status code. The method is called by the `exit()` methods of the `Runtime` and `System` classes.

  The `checkExit()` method of `SecurityManager` always throws a `SecurityException`.

### checkLink

#### `public void checkLink(String lib)`

Parameters

  `lib`

    The name of a library.

Throws

  `SecurityException`

    If the caller does not have permission to load the specified library.

Description

  This method decides whether to allow the specified library to be loaded. An implementation of the method should throw a `SecurityException` to deny permission to load the specified library. The method is called by the `load()` and `loadLibrary()` methods of the `Runtime` and `System` classes.

  The `checkLink()` method of `SecurityManager` always throws a `SecurityException`.

### checkListen

#### `public void checkListen(int port)`

Parameters

  `port`

    A port number.

Throws

  `SecurityException`

    If the caller does not have permission to listen on the specified port.

Description

  This method decides whether or not to allow the caller to listen on the specified port. An implementation of the method should throw a `SecurityException` to deny permission to listen on the specified port. The method is called by the constructors of the `java.net.ServerSocket` class and by the constructor of the `java.net.DatagramSocket` class that takes one argument.

  The `checkListen()` method of `SecurityManager` always throws a `SecurityException`.

### checkMemberAccess

#### `public void checkMemberAccess(Class clazz, int which)`

Availability

  New as of JDK 1.1

Parameters

  `clazz`

    A `Class` object.

  `which`

    The value `Member.PUBLIC` for the set of all `public` members including inherited members or the value `Member.DECLARED` for the set of all declared members of the specified class or interface.

Throws

  `SecurityException`

    If the caller does not have permission to access the members of the specified class or interface.

Description

  This method decides whether or not to allow access to the members of the specified `Class` object. An implementation of the method should throw a `SecurityException` to deny permission to access the members. Methods of the `Class` class that call this method include `getField()`, `getFields()`, `getDeclaredField()`, `getDeclaredFields()`, `getMethod()`, `getMethods()`, `getDeclaredMethod()`, `getDeclaredMethods()`, `getConstructor()`, `getConstructors()`, `getDeclaredConstructor()`, `getDeclaredConstructors()`, and `getDeclaredClasses()`.

  The `checkMemberAccess()` method of `SecurityManager` always throws a `SecurityException`.

### checkMulticast

#### `public void checkMulticast(InetAddress maddr)`

Availability

  New as of JDK 1.1

Parameters

  `maddr`

    An `InetAddress` object that represents a multicast address.

Throws

  `SecurityException`

    If the current thread does not have permission to use the specified multicast address.

Description

  This method decides whether or not to allow the current thread to use the specified multicast `InetAddress`. An implementation of the method should throw a `SecurityException` to deny permission to use the multicast address. The method is called by the `send()` method of `java.net.DatagramSocket` if the packet is being sent to a multicast address. The method is also called by the `joinGroup()` and `leaveGroup()` methods of `java.net.MulticastSocket`.

  The `checkMulticast()` method of `SecurityManager` always throws a `SecurityException`.

#### `public void checkMulticast(InetAddress maddr, byte ttl)`

Availability

  New as of JDK 1.1

Parameters

  `maddr`

    An `InetAddress` object that represents a multicast address.

  `ttl`

    The time-to-live (TTL) value.

Throws

  `SecurityException`

    If the current thread does not have permission to use the specified multicast address and TTL value.

Description

  This method decides whether or not to allow the current thread to use the specified multicast `InetAddress` and TTL value. An implementation of the method should throw a `SecurityException` to deny permission to use the multicast address. The method is called by the `send()` method of `java.net.MulticastSocket`.

  The `checkMulticast()` method of `SecurityManager` always throws a `SecurityException`.

### checkPackageAccess

#### `public void checkPackageAccess(String pkg)`

Parameters

  `pkg`

    The name of a package.

Throws

  `SecurityException`

    If the caller does not have permission to access the specified package.

Description

  This method decides whether or not to allow the specified package to be accessed. An implementation of the method should throw a `SecurityException` to deny permission to access the specified package. The method is intended to be called by implementations of the `loadClass()` method in subclasses of the `ClassLoader` class.

  The `checkPackageAccess()` method of `SecurityManager` always throws a `SecurityException`.

### checkPackageDefinition

#### `public void checkPackageDefinition(String pkg)`

Parameters

  `pkg`

    The name of a package.

Throws

  `SecurityException`

    If the caller does not have permission to define classes in the specified package.

Description

  This method decides whether or not to allow the caller to define classes in the specified package. An implementation of the method should throw a `SecurityException` to deny permission to create classes in the specified package. The method is intended to be called by implementations of the `loadClass()` method in subclasses of the `ClassLoader` class.

  The `checkPackageDefinition()` method of `SecurityManager` always throws a `SecurityException`.

### checkPrintJobAccess

#### `public void checkPrintJobAccess()`

Availability

  New as of JDK 1.1

Throws

  `SecurityException`

    If the caller does not have permission to initiate a print job request.

Description

  This method decides whether or not to allow the caller to initiate a print job request. An implementation of the method should throw a `SecurityException` to deny permission to initiate the request.

  The `checkPrintJobAccess()` method of `SecurityManager` always throws a `SecurityException`.

### checkPropertiesAccess

#### `public void checkPropertiesAccess()`

Throws

  `SecurityException`

    If the caller does not have permission to access the system properties.

Description

  This method decides whether or not to allow the caller to access and modify the system properties. An implementation of the method should throw a `SecurityException` to deny permission to access and modify the properties. Methods of the `System` class that call this method include `getProperties()` and `setProperties()`.

  The `checkPropertiesAccess()` method of `SecurityManager` always throws a `SecurityException`.

### checkPropertyAccess

#### `public void checkPropertyAccess(String key)`

Parameters

  `key`

    The name of an individual system property.

Throws

  `SecurityException`

    If the caller does not have permission to access the specified system property.

Description

  This method decides whether or not to allow the caller to access the specified system property. An implementation of the method should throw a `SecurityException` to deny permission to access the property. The method is called by the `getProperty()` method of the `System` class.

  The `checkPropertyAccess()` method of `SecurityManager` always throws a `SecurityException`.

### checkRead

#### `public void checkRead(FileDescriptor fd)`

Parameters

  `fd`

    A reference to a `FileDescriptor` object.

Throws

  `SecurityException`

    If the caller does not have permission to read from the given file descriptor.

Description

  This method decides whether or not to allow the caller to read from the specified file descriptor. An implementation of the method should throw a `SecurityException` to deny permission to read from the file descriptor. The method is called by the constructor of the `java.io.FileInputStream` class that takes a `FileDescriptor` argument.

  The `checkRead()` method of `SecurityManager` always throws a `SecurityException`.

#### `public void checkRead(String file)`

Parameters

  `file`

    The name of a file.

Throws

  `SecurityException`

    If the caller does not have permission to read from the named file.

Description

  This method decides whether or not to allow the caller to read from the named file. An implementation of the method should throw a `SecurityException` to deny permission to read from the file. The method is called by constructors of the `java.io.FileInputStream` and `java.io.RandomAccessFile` classes, as well as by the `canRead()`, `exists()`, `isDirectory()`, `isFile()`, `lastModified()`, `length()`, and `list()` methods of the `java.io.File` class.

  The `checkRead()` method of `SecurityManager` always throws a `SecurityException`.

#### `public void checkRead(String file, Object context)`

Parameters

  `file`

    The name of a file.

  `context`

    A security context object returned by this object's `getSecurityContext()` method.

Throws

  `SecurityException`

    If the specified security context does not have permission to read from the named file.

Description

  This method decides whether or not to allow the specified security context to read from the named file. An implementation of the method should throw a `SecurityException` to deny permission to read from the file.

  The `checkRead()` method of `SecurityManager` always throws a `SecurityException`.

### checkSecurityAccess

#### `public void checkSecurityAccess(String action)`

Availability

  New as of JDK 1.1

Parameters

  `action`

    A string that specifies a security action.

Throws

  `SecurityException`

    If the caller does not have permission to perform the specified security action.

Description

  This method decides whether to allow the caller to perform the specified security action. An implementation of the method should throw a `SecurityException` to deny permission to perform the action. The method is called by many of the methods in the `java.security.Identity` and `java.security.Security` classes.

  The `checkSecurityAccess()` method of `SecurityManager` always throws a `SecurityException`.

### checkSetFactory

#### `public void checkSetFactory()`

Throws

  `SecurityException`

    If the caller does not have permission to set the factory class to be used by another class.

Description

  This method decides whether to allow the caller to set the factory class to be used by another class. An implementation of the method should throw a `SecurityException` to deny permission to set the factory class. The method is called by the `setSocketFactory()` method of the `java.net.ServerSocket` class, the `setSocketImplFactory()` method of the `java.net.Socket` class, the `setURLStreamHandlerFactory()` method of the `java.net.URL` class, and the `setContentHandlerFactory()` method of the `java.net.URLConnection` class.

  The `checkSetFactory()` method of `SecurityManager` always throws a `SecurityException`.

### checkSystemClipboardAccess

#### `public void checkSystemClipboardAccess()`

Availability

  New as of JDK 1.1

Throws

  `SecurityException`

    If the caller does not have permission to access the system clipboard.

Description

  This method decides whether or not to allow the caller to access the system clipboard. An implementation of the method should throw a `SecurityException` to deny permission to access the system clipboard.

  The `checkSystemClipboardAccess()` method of `SecurityManager` always throws a `SecurityException`.

### checkTopLevelWindow

#### `public boolean checkTopLevelWindow(Object window)`

Parameters

  `window`

    A window object.

Returns

  `true` if the caller is trusted to put up the specified top-level window; otherwise `false`.

Description

  This method decides whether or not to trust the caller to put up the specified top-level window. An implementation of the method should return `false` to indicate that the caller is not trusted. In this case, the hosting environment can still decide to display the window, but the window should include a visual indication that it is not trusted. If the caller is trusted, the method should return `true`, and the window can be displayed without any special indication.

  The `checkTopLevelWindow()` method of `SecurityManager` always returns `false`.

### checkWrite

#### `public void checkWrite(FileDescriptor fd)`

Parameters

  `fd`

    A `FileDescriptor` object.

Throws

  `SecurityException`

    If the caller does not have permission to write to the given file descriptor.

Description

  This method decides whether or not to allow the caller to write to the specified file descriptor. An implementation of the method should throw a `SecurityException` to deny permission to write to the file descriptor. The method is called by the constructor of the `java.io.FileOutputStream` class that takes a `FileDescriptor` argument.

  The `checkWrite()` method of `SecurityManager` always throws a `SecurityException`.

#### `public void checkWrite(String file)`

Parameters

  `file`

    The name of a file.

Throws

  `SecurityException`

    If the caller does not have permission to read from the named file.

Description

  This method decides whether or not to allow the caller to write to the named file. An implementation of the method should throw a `SecurityException` to deny permission to write to the file. The method is called by constructors of the `java.io.FileOutputStream` and `java.io.RandomAccessFile` classes, as well as by the `canWrite()`, `mkdir()`, and `renameTo()` methods of the `java.io.File` class.

  The `checkWrite()` method of `SecurityManager` always throws a `SecurityException`.

### getInCheck

#### `public boolean getInCheck()`

Returns

  `true` if a security check is in progress; otherwise `false`.

Description

  This method returns the value of the `SecurityManager` object's `inCheck` variable, which is `true` if a security check is in progress and `false` otherwise.

### getSecurityContext

#### `public Object getSecurityContext()`

Returns

  An implementation-dependent object that contains enough information about the current execution environment to perform security checks at a later time.

Description

  This method is meant to create an object that encapsulates information about the current execution environment. The resulting security context object is used by specific versions of the `checkConnect()` and `checkRead()` methods. The intent is that such a security context object can be used by a trusted method to determine whether or not another, untrusted method can perform a particular operation.

  The `getSecurityContext()` method of `SecurityManager` simply returns `null`. This method should be overridden to return an appropriate security context object for the security policy that is being implemented.

### getThreadGroup

#### `public ThreadGroup getThreadGroup()`

Availability

  New as of JDK 1.1

Returns

  A `ThreadGroup` in which to place any threads that are created when this method is called.

Description

  This method returns the appropriate parent `ThreadGroup` for any threads that are created when the method is called. The `getThreadGroup()` method of `SecurityManager` simply returns the `ThreadGroup` of the current thread. This method should be overridden to return an appropriate `ThreadGroup`.

## Protected Instance Methods

### classDepth

#### `protected native int classDepth(String name)`

Parameters

  `name`

    The fully qualified name of a class.

Returns

  The number of pending method invocations from the top of the stack to a call to a method of the given class; `-1` if no stack frame in the current thread is associated with a call to a method in the given class.

Description

  This method returns the number of pending method invocations between this method invocation and an invocation of a method associated with the named class.

### classLoaderDepth

#### `protected native int classLoaderDepth()`

Returns

  The number of pending method invocations from the top of the stack to a call to a method that is associated with a class that was loaded by a `ClassLoader` object; `-1` if no stack frame in the current thread is associated with a call to such a method.

Description

  This method returns the number of pending method invocations between this method invocation and an invocation of a method associated with a class that was loaded by a `ClassLoader` object.

### currentClassLoader

#### `protected native ClassLoader currentClassLoader()`

Returns

  The most recent `ClassLoader` object executing on the stack.

Description

  This method finds the most recent pending invocation of a method associated with a class that was loaded by a `ClassLoader` object. The method then returns the `ClassLoader` object that loaded that class.

### currentLoadedClass

#### `protected Class currentLoadedClass()`

Availability

  New as of JDK 1.1

Returns

  The most recent `Class` object loaded by a `ClassLoader`.

Description

  This method finds the most recent pending invocation of a method associated with a class that was loaded by a `ClassLoader` object. The method then returns the `Class` object for that class.

### getClassContext

#### `protected native Class[] getClassContext()`

Returns

  An array of `Class` objects that represents the current execution stack.

Description

  This method returns an array of `Class` objects that represents the current execution stack. The length of the array is the number of pending method calls on the current thread's stack, not including the call to `getClassContext()`. Each element of the array references a `Class` object that describes the class associated with the corresponding method call. The first element of the array corresponds to the most recently called method, the second element is that method's caller, and so on.

### inClass

#### `protected boolean inClass(String name)`

Parameters

  `name`

    The fully qualified name of a class.

Returns

  `true` if there is a pending method invocation on the stack for a method of the given class; otherwise `false`.

Description

  This method determines whether or not there is a pending method invocation that is associated with the named class.

### inClassLoader

#### `protected boolean inClassLoader()`

Returns

  `true` if there is a pending method invocation on the stack for a method of a class that was loaded by a `ClassLoader` object; otherwise `false`.

Description

  This method determines whether or not there is a pending method invocation that is associated with a class that was loaded by a `ClassLoader` object. The method returns `true` only if the `currentClassLoader()` method does not return `null`.

## Inherited Methods

Method | Inherited From | Method | Inherited From
--- | --- | --- | ---
`clone()` | `Object` | `equals(Object)` | `Object`
`finalize()` | `Object` | `getClass()` | `Object`
`hashCode()` | `Object` | `notify()` | `Object`
`notifyAll()` | `Object` | `toString()` | `Object`
`wait()` | `Object` | `wait(long)` | `Object`
`wait(long, int)` | `Object` |  |

## See Also

`Class`, `ClassLoader`, `DatagramSocket`, `File`, `FileDescriptor`, `FileInputStream`, `FileOutputStream`, `InetAddress`, `MulticastSocket`, `Object`, `RandomAccessFile`, `Runtime`, `SecurityException`, `ServerSocket`, `Socket`, `System`, `Thread`, `ThreadGroup`, `Toolkit`, `URL`, `URLConnection`

SecurityException |  | Short