Chapter 15
The java.net Package

InetAddress

Name

InetAddress

Synopsis

Class Name:

java.net.InetAddress

Superclass:

java.lang.Object

Immediate Subclasses:

None

Interfaces Implemented:

java.io.Serializable

Availability:

JDK 1.0 or later

The InetAddress class encapsulates an Internet Protocol (IP) address. InetAddress objects are used by the various classes that are responsible for specifying the destination addresses of outbound network packets, such as DatagramSocket, MulticastSocket, and Socket. InetAddress does not provide any public constructors. Instead, you must use the static methods getAllByName(), getByName(), and getLocalHost() to create InetAddress objects.

Class Summary

public final class java.net.InetAddress extends java.lang.Object
                   implements java.io.Serializable {
  // Class Methods
  public static InetAddress[] getAllByName(String host);
  public static InetAddress getByName(String host);
  public static InetAddress getLocalHost();
  // Instance Methods
  public boolean equals(Object obj); 
  public byte[] getAddress();
  public String getHostAddress();                // New in 1.1
  public String getHostName();
  public int hashCode();
  public boolean isMulticastAddress();           // New in 1.1
  public String toString();
}

Class Methods

getAllByName

 public static InetAddress[] getAllByName(String host) throws UnknownHostException

Parameters

host: A String that contains a hostname.

Returns

An array of InetAddress objects that corresponds to the given name.

Throws

SecurityException

If the application is not allowed to connect to host.

UnknownHostException

If host cannot be resolved.

Description

This method finds all of the IP addresses that correspond to the given hostname. The hostname can be a machine name, such as "almond.nuts.com", or a string representation of an IP address, such as "208.25.146.1".

getByName

 public static InetAddress getByName(String host) throws UnknownHostException

Parameters

host: A String that contains a host name.

Returns

An InetAddress that corresponds to the given name.

Throws

SecurityException

If the application is not allowed to connect to host.

UnknownHostException

If host cannot be resolved.

Description

This method returns the primary IP address that correspond to the given hostname. The hostname can be a machine name, such as "almond.nuts.com", or a string representation of an IP address, such as "208.25.146.1".

getLocalHost

 public static InetAddress getLocalHost() throws UnknownHostException

Returns

An InetAddress that corresponds to the name of the local machine.

Throws

SecurityException

If the application is not allowed to connect to host.

UnknownHostException

If host cannot be resolved.

Description

This method finds the IP address of the local machine.

Instance Methods

equals

public boolean equals(Object obj)

Parameters

obj: The object to be compared with this object.

Returns

true if the objects are equivalent; false if they are not.

Overrides

Object.equals()

Description

This method returns true if obj is an instance of InetAddress that specifies the same IP address as the object this method is associated with.

getAddress

public byte[] getAddress()

Returns

A byte array with elements that correspond to the bytes of the IP address that this object represents.

Description

This method returns the IP address associated with this object as an array of bytes in network order. That means that the first element of the array contains the highest order byte, and the last element of the array contains the lowest order byte.

getHostAddress

public String getHostAddress()

Availability

New as of JDK 1.1

Returns

A String that contains the IP address of this object.

Description

This method returns a string representation of the IP address associated with this object. For example: "206.175.64.78".

getHostName

public String getHostName()

Returns

The hostname associated with this object.

Description

In most cases, this method returns the hostname that corresponds to the IP address associated with this object. However, there are a few special cases:

If the address associated with this object is address of the local machine, the method may return null.
If the method cannot determine a home name to go with the address associated with this object, the method returns a string representation of the address.
If the application is not allowed to know the hostname, the method returns a string representation of the address.

hashCode

public int hashCode()

Returns

The hashcode based on the IP address of the object.

Overrides

Object.hashCode()

Description

This method returns a hashcode for this object, based on the IP address associated with this object.

isMulticastAddress

public boolean isMulticastAddress()

Availability

New as of JDK 1.1

Returns

true if this object represents a multicast address; false otherwise.

Description

This method returns a flag that indicates if this object represents an IP multicast address. A multicast address is a Class D address, which means that its four highest-order bits are set to 1110. In other words, multicast addresses are in the range 224.0.0.1 through 239.255.255.255 inclusive.

toString

public String toString()

Returns

The string representation of this InetAddress.

Overrides

Object.toString()

Description

This method returns a String that contains both the hostname and IP address of this object.

Inherited Methods

Method	Inherited From	Method	Inherited From
`clone()`	`Object`	`finalize()`	`Object`
`getClass()`	`Object`	`notify()`	`Object`
`notifyAll()`	`Object`	`wait()`	`Object`
`wait(long)`	`Object`	`wait(long, int)`	`Object`