Class NetworkInterface

java.lang.Object
java.net.NetworkInterface
public final class NetworkInterface extends Object
This class represents a Network Interface.

A Network Interface is an abstraction encapsulating the characteristics of a Network Interface Controller, or Virtual Network adapter, which is a system hardware/software component connecting a computer, or host system, to a computer network. A Network Interface can be physical or virtual. A Network Interface has a name, zero or more assigned IP addresses, zero or more MAC Addresses, and may have an index. The name is highly platform specific but a name such as "le0" is typical; it may not be unique. The index is a highly platform specific number that identifies the interface. The network configuration may change during the lifetime of the JVM. For example, the set of IP addresses assigned to a network interface can be transient and dynamically allocated, and may change at any time.

When obtaining a NetworkInterface instance, part of its configuration (such as its name and the list of assigned IP addresses), is reflective of its configuration at creation time. Obtaining an updated view of the network configuration may require looking up a network interface again in order to obtain a new instance.

Network interface instances are typically used to identify the local interface on which a multicast group is joined.

Since:
1.4

  • Method Details

    • getName

      public String getName()
      Get the name of this network interface.
      Returns:
      the name of this network interface

    • getInetAddresses

      public Enumeration<InetAddress> getInetAddresses()
      Get an Enumeration of the InetAddresses bound to this network interface.
      Returns:
      an Enumeration object with the InetAddresses bound to this network interface
      See Also:

    • inetAddresses

      public Stream<InetAddress> inetAddresses()
      Get a Stream of the InetAddresses bound to this network interface.
      Returns:
      a Stream object with the InetAddresses bound to this network interface
      Since:
      9

    • getInterfaceAddresses

      public List<InterfaceAddress> getInterfaceAddresses()
      Get a List of the InterfaceAddresses of this network interface.
      Returns:
      a List object with the InterfaceAddress 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
      See Also:

    • subInterfaces

      public Stream<NetworkInterface> subInterfaces()
      Get a Stream of all subinterfaces (also known as virtual interfaces) attached to this network interface.
      Returns:
      a Stream object with all of the subinterfaces of this network interface
      Since:
      9

    • 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:

    • 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:

    • 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 an Enumeration of 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.
      Returns:
      an Enumeration of NetworkInterfaces found on this machine
      Throws:
      SocketException - if an I/O error occurs, or if the platform does not have at least one configured network interface.
      See Also:

    • networkInterfaces

      public static Stream<NetworkInterface> networkInterfaces() throws SocketException
      Returns a Stream of all the interfaces on this machine. The Stream contains at least one interface, possibly representing a loopback interface that only supports communication between entities on this machine.
      Returns:
      a Stream of NetworkInterfaces found on this machine
      Throws:
      SocketException - if an I/O error occurs, or if the platform does not have at least one configured network interface.
      Since:
      9

    • 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.
      Returns:
      a byte array containing the address, or null if the address doesn't exist or is not accessible
      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 the name and the set of InetAddresses bound to the interfaces are equal.

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

    • hashCode

      public int hashCode()
      Description copied from class: Object
      Returns a hash code value for this 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 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 equals 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.
      Overrides:
      hashCode in class Object
      Returns:
      a hash code value for this object
      See Also:

    • toString

      public String toString()
      Description copied from class: Object
      Returns a string representation of the object. Satisfying this method's contract implies a non-null result must be returned.
      Overrides:
      toString in class Object
      Returns:
      a string representation of the object