Uses of Class java.io.FileDescriptor (Java SE 10 & JDK 10 )

## 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 | 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 | Description
    --- | --- | ---
    `FileDescriptor` | FileInputStream.`getFD()` | Returns the `FileDescriptor` object that represents the connection to the actual file in the file system being used by this `FileInputStream`.
    `FileDescriptor` | FileOutputStream.`getFD()` | Returns the file descriptor associated with this stream.
    `FileDescriptor` | RandomAccessFile.`getFD()` | Returns the opaque file descriptor object associated with this stream.

    Constructors in java.io with parameters of type FileDescriptor
    Constructor | 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
    Modifier and Type | Method | 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 | Description
    --- | --- | ---
    `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
    Modifier and Type | Method | Description
    --- | --- | ---
    `protected FileDescriptor` | DatagramSocketImpl.`getFileDescriptor()` | Gets the datagram socket file descriptor.
    `protected FileDescriptor` | SocketImpl.`getFileDescriptor()` | Returns the value of this socket's `fd` field.