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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

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. Returns null if no network interfaces could be found 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^TM 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.