## Uses of Class
java.io.FileDescriptor

Packages that use FileDescriptor
java.io: Provides for system input and output through data streams, serialization and the file system.
java.lang: Provides classes that are fundamental to the design of the Java programming language.
java.net: Provides the classes for implementing networking applications.

### Uses of FileDescriptor in java.io

Fields in java.io declared as FileDescriptor
`static FileDescriptor` FileDescriptor.`err` A handle to the standard error stream.
`static FileDescriptor` FileDescriptor.`in` A handle to the standard input stream.
`static FileDescriptor` FileDescriptor.`out` A handle to the standard output stream.

Methods in java.io that return FileDescriptor
`FileDescriptor` RandomAccessFile.`getFD()` Returns the opaque file descriptor object associated with this stream.
`FileDescriptor` FileOutputStream.`getFD()` Returns the file descriptor associated with this stream.
`FileDescriptor` FileInputStream.`getFD()` Returns the `FileDescriptor` object that represents the connection to the actual file in the file system being used by this `FileInputStream`.

Constructors in java.io with parameters of type FileDescriptor
Constructor and Description
`FileInputStream(FileDescriptor fdObj)` Creates a `FileInputStream` by using the file descriptor `fdObj`, which represents an existing connection to an actual file in the file system.
`FileOutputStream(FileDescriptor fdObj)` Creates a file output stream to write to the specified file descriptor, which represents an existing connection to an actual file in the file system.
`FileReader(FileDescriptor fd)` Creates a new `FileReader`, given the `FileDescriptor` to read from.
`FileWriter(FileDescriptor fd)` Constructs a FileWriter object associated with a file descriptor.

### Uses of FileDescriptor in java.lang

Methods in java.lang with parameters of type FileDescriptor
`void` SecurityManager.`checkRead(FileDescriptor fd)` Throws a `SecurityException` if the calling thread is not allowed to read from the specified file descriptor.
`void` SecurityManager.`checkWrite(FileDescriptor fd)` Throws a `SecurityException` if the calling thread is not allowed to write to the specified file descriptor.

### Uses of FileDescriptor in java.net

Fields in java.net declared as FileDescriptor
`protected FileDescriptor` DatagramSocketImpl.`fd` The file descriptor object.
`protected FileDescriptor` SocketImpl.`fd` The file descriptor object for this socket.

Methods in java.net that return FileDescriptor
`protected FileDescriptor` DatagramSocketImpl.`getFileDescriptor()` Gets the datagram socket file descriptor.
`protected FileDescriptor` SocketImpl.`getFileDescriptor()` Returns the value of this socket's `fd` field.