## Uses of Class
java.io.FileDescriptor

- Packages that use FileDescriptor
  Package | Description
  --- | ---
  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
    Modifier and Type | Field and Description
    --- | ---
    `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
    Modifier and Type | Method and Description
    --- | ---
    `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 an output file 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
    Modifier and Type | Method and Description
    --- | ---
    `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
    Modifier and Type | Field and Description
    --- | ---
    `protected FileDescriptor` | SocketImpl.`fd` The file descriptor object for this socket.
    `protected FileDescriptor` | DatagramSocketImpl.`fd` The file descriptor object.

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

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