NetworkInterface (Java Platform SE 8 )
Keywords: java.net.NetworkInterface class
Date: 2016-07-28

compact1, compact2, compact3
java.net

## Class NetworkInterface

- java.lang.Object
- - java.net.NetworkInterface

-     public final class NetworkInterface
      extends Object

  This class represents a Network Interface made up of a name, and a list of IP addresses assigned to this interface. It is used to identify the local interface on which a multicast group is joined. Interfaces are normally known by names such as "le0".
  Since:
    1.4

- - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `equals(Object obj)` Compares this object against the specified object.
    `static NetworkInterface` | `getByIndex(int index)` Get a network interface given its index.
    `static NetworkInterface` | `getByInetAddress(InetAddress addr)` Convenience method to search for a network interface that has the specified Internet Protocol (IP) address bound to it.
    `static NetworkInterface` | `getByName(String name)` Searches for the network interface with the specified name.
    `String` | `getDisplayName()` Get the display name of this network interface.
    `byte[]` | `getHardwareAddress()` Returns the hardware address (usually MAC) of the interface if it has one and if it can be accessed given the current privileges.
    `int` | `getIndex()` Returns the index of this network interface.
    `Enumeration<InetAddress>` | `getInetAddresses()` Convenience method to return an Enumeration with all or a subset of the InetAddresses bound to this network interface.
    `List<InterfaceAddress>` | `getInterfaceAddresses()` Get a List of all or a subset of the `InterfaceAddresses` of this network interface.
    `int` | `getMTU()` Returns the Maximum Transmission Unit (MTU) of this interface.
    `String` | `getName()` Get the name of this network interface.
    `static Enumeration<NetworkInterface>` | `getNetworkInterfaces()` Returns all the interfaces on this machine.
    `NetworkInterface` | `getParent()` Returns the parent NetworkInterface of this interface if this is a subinterface, or `null` if it is a physical (non virtual) interface or has no parent.
    `Enumeration<NetworkInterface>` | `getSubInterfaces()` Get an Enumeration with all the subinterfaces (also known as virtual interfaces) attached to this network interface.
    `int` | `hashCode()` Returns a hash code value for the object.
    `boolean` | `isLoopback()` Returns whether a network interface is a loopback interface.
    `boolean` | `isPointToPoint()` Returns whether a network interface is a point to point interface.
    `boolean` | `isUp()` Returns whether a network interface is up and running.
    `boolean` | `isVirtual()` Returns whether this interface is a virtual interface (also called subinterface).
    `boolean` | `supportsMulticast()` Returns whether a network interface supports multicasting or not.
    `String` | `toString()` Returns a string representation of the object.

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Method Detail

    - #### getName

          public String getName()

      Get the name of this network interface.
      Returns:
        the name of this network interface

    - #### getInetAddresses

          public Enumeration<InetAddress> getInetAddresses()

      Convenience method to return an Enumeration with all or a subset of the InetAddresses bound to this network interface.

      If there is a security manager, its `checkConnect` method is called for each InetAddress. Only InetAddresses where the `checkConnect` doesn't throw a SecurityException will be returned in the Enumeration. However, if the caller has the `NetPermission`("getNetworkInformation") permission, then all InetAddresses are returned.

      Returns:
        an Enumeration object with all or a subset of the InetAddresses bound to this network interface

    - #### getInterfaceAddresses

          public List<InterfaceAddress> getInterfaceAddresses()

      Get a List of all or a subset of the `InterfaceAddresses` of this network interface.

      If there is a security manager, its `checkConnect` method is called with the InetAddress for each InterfaceAddress. Only InterfaceAddresses where the `checkConnect` doesn't throw a SecurityException will be returned in the List.

      Returns:
        a `List` object with all or a subset of the InterfaceAddresss of this network interface
      Since:
        1.6

    - #### getSubInterfaces

          public Enumeration<NetworkInterface> getSubInterfaces()

      Get an Enumeration with all the subinterfaces (also known as virtual interfaces) attached to this network interface.

      For instance eth0:1 will be a subinterface to eth0.

      Returns:
        an Enumeration object with all of the subinterfaces of this network interface
      Since:
        1.6

    - #### getParent

          public NetworkInterface getParent()

      Returns the parent NetworkInterface of this interface if this is a subinterface, or `null` if it is a physical (non virtual) interface or has no parent.
      Returns:
        The `NetworkInterface` this interface is attached to.
      Since:
        1.6

    - #### getIndex

          public int getIndex()

      Returns the index of this network interface. The index is an integer greater or equal to zero, or `-1` for unknown. This is a system specific value and interfaces with the same name can have different indexes on different machines.
      Returns:
        the index of this network interface or `-1` if the index is unknown
      Since:
        1.7
      See Also:
        `getByIndex(int)`

    - #### getDisplayName

          public String getDisplayName()

      Get the display name of this network interface. A display name is a human readable String describing the network device.
      Returns:
        a non-empty string representing the display name of this network interface, or null if no display name is available.

    - #### getByName

          public static NetworkInterface getByName(String name)
                                            throws SocketException

      Searches for the network interface with the specified name.
      Parameters:
        `name` - The name of the network interface.
      Returns:
        A `NetworkInterface` with the specified name, or `null` if there is no network interface with the specified name.
      Throws:
        `SocketException` - If an I/O error occurs.
        `NullPointerException` - If the specified name is `null`.

    - #### getByIndex

          public static NetworkInterface getByIndex(int index)
                                             throws SocketException

      Get a network interface given its index.
      Parameters:
        `index` - an integer, the index of the interface
      Returns:
        the NetworkInterface obtained from its index, or `null` if there is no interface with such an index on the system
      Throws:
        `SocketException` - if an I/O error occurs.
        `IllegalArgumentException` - if index has a negative value
      Since:
        1.7
      See Also:
        `getIndex()`

    - #### getByInetAddress

          public static NetworkInterface getByInetAddress(InetAddress addr)
                                                   throws SocketException

      Convenience method to search for a network interface that has the specified Internet Protocol (IP) address bound to it.

      If the specified IP address is bound to multiple network interfaces it is not defined which network interface is returned.

      Parameters:
        `addr` - The `InetAddress` to search with.
      Returns:
        A `NetworkInterface` or `null` if there is no network interface with the specified IP address.
      Throws:
        `SocketException` - If an I/O error occurs.
        `NullPointerException` - If the specified address is `null`.

    - #### getNetworkInterfaces

          public static Enumeration<NetworkInterface> getNetworkInterfaces()
                                                                    throws SocketException

      Returns all the interfaces on this machine. The `Enumeration` contains at least one element, possibly representing a loopback interface that only supports communication between entities on this machine. NOTE: can use getNetworkInterfaces()+getInetAddresses() to obtain all IP addresses for this node
      Returns:
        an Enumeration of NetworkInterfaces found on this machine
      Throws:
        `SocketException` - if an I/O error occurs.

    - #### isUp

          public boolean isUp()
                       throws SocketException

      Returns whether a network interface is up and running.
      Returns:
        `true` if the interface is up and running.
      Throws:
        `SocketException` - if an I/O error occurs.
      Since:
        1.6

    - #### isLoopback

          public boolean isLoopback()
                             throws SocketException

      Returns whether a network interface is a loopback interface.
      Returns:
        `true` if the interface is a loopback interface.
      Throws:
        `SocketException` - if an I/O error occurs.
      Since:
        1.6

    - #### isPointToPoint

          public boolean isPointToPoint()
                                 throws SocketException

      Returns whether a network interface is a point to point interface. A typical point to point interface would be a PPP connection through a modem.
      Returns:
        `true` if the interface is a point to point interface.
      Throws:
        `SocketException` - if an I/O error occurs.
      Since:
        1.6

    - #### supportsMulticast

          public boolean supportsMulticast()
                                    throws SocketException

      Returns whether a network interface supports multicasting or not.
      Returns:
        `true` if the interface supports Multicasting.
      Throws:
        `SocketException` - if an I/O error occurs.
      Since:
        1.6

    - #### getHardwareAddress

          public byte[] getHardwareAddress()
                                    throws SocketException

      Returns the hardware address (usually MAC) of the interface if it has one and if it can be accessed given the current privileges. If a security manager is set, then the caller must have the permission `NetPermission`("getNetworkInformation").
      Returns:
        a byte array containing the address, or `null` if the address doesn't exist, is not accessible or a security manager is set and the caller does not have the permission NetPermission("getNetworkInformation")
      Throws:
        `SocketException` - if an I/O error occurs.
      Since:
        1.6

    - #### getMTU

          public int getMTU()
                     throws SocketException

      Returns the Maximum Transmission Unit (MTU) of this interface.
      Returns:
        the value of the MTU for that interface.
      Throws:
        `SocketException` - if an I/O error occurs.
      Since:
        1.6

    - #### isVirtual

          public boolean isVirtual()

      Returns whether this interface is a virtual interface (also called subinterface). Virtual interfaces are, on some systems, interfaces created as a child of a physical interface and given different settings (like address or MTU). Usually the name of the interface will the name of the parent followed by a colon (:) and a number identifying the child since there can be several virtual interfaces attached to a single physical interface.
      Returns:
        `true` if this interface is a virtual interface.
      Since:
        1.6

    - #### equals

          public boolean equals(Object obj)

      Compares this object against the specified object. The result is `true` if and only if the argument is not `null` and it represents the same NetworkInterface as this object.

      Two instances of `NetworkInterface` represent the same NetworkInterface if both name and addrs are the same for both.

      Overrides:
        `equals` in class `Object`
      Parameters:
        `obj` - the object to compare against.
      Returns:
        `true` if the objects are the same; `false` otherwise.
      See Also:
        `InetAddress.getAddress()`

    - #### hashCode

          public int hashCode()

      Description copied from class: `Object`
      Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by `HashMap`.

      The general contract of `hashCode` is:

      - Whenever it is invoked on the same object more than once during an execution of a Java application, the `hashCode` method must consistently return the same integer, provided no information used in `equals` comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
      - If two objects are equal according to the `equals(Object)` method, then calling the `hashCode` method on each of the two objects must produce the same integer result.
      - It is not required that if two objects are unequal according to the `Object.equals(java.lang.Object)` method, then calling the `hashCode` method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

      As much as is reasonably practical, the hashCode method defined by class `Object` does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java™ programming language.)

      Overrides:
        `hashCode` in class `Object`
      Returns:
        a hash code value for this object.
      See Also:
        `Object.equals(java.lang.Object)`, `System.identityHashCode(java.lang.Object)`

    - #### toString

          public String toString()

      Description copied from class: `Object`
      Returns a string representation of the object. In general, the `toString` method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

      The `toString` method for class `Object` returns a string consisting of the name of the class of which the object is an instance, the at-sign character ``@`', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

      >      getClass().getName() + '@' + Integer.toHexString(hashCode())

      Overrides:
        `toString` in class `Object`
      Returns:
        a string representation of the object.

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