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Then it passes that object's reference to the println method causing the overridden toString method belonging the InetAddress object to be executed.
| Listing 3 - Get InetAddress object for localhost. |
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System.out.println();//blank line
System.out.println("Get and display current " +"InetAddress of LocalHost");
InetAddress address = InetAddress.getLocalHost();System.out.println(address); |
The screen output for localhost
The string returned by the overridden toString method of the InetAddress object is shown by the second line in Figure 3 .
| Figure 3 - The IP Address for my localhost. |
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Get and display current InetAddress of LocalHost
dell8700/192.168.2.16 |
Everything to the left of the slash is the name of the computer. Everything to the right of the slash is the IP address.
A local area network
Note that this is not the IP address by which the world sees my computer on the Internet. Instead, thisis one of several computers on a local area network. This is the address thatwas assigned to this computer by the network router.
I can find the IP address that my cable modem presents to the world by entering the following text into theGoogle search box without the quotation marks: "get ip address"
As you can see, the second line in Figure 3 contains both the name and the IP address separated by a slash character.
Extract name and IP address of my localhost
Assume that you have a reference to an InetAddress object and for some reason you need to extract the name and IP address as separate String objects. (We will need to do this in a future module.) The InetAddress class provides two methods that allow you to do that.
The code in Listing 4 calls the getHostName and the getHostAddress methods on the reference to the InetAddress object and displays the strings returned by those methods.
| Listing 4 - Extract name and IP address of my localhost. |
|---|
System.out.println();//blank line
System.out.println("Extract and display current " +"name of LocalHost");
System.out.println(address.getHostName());System.out.println();//blank line
System.out.println("Extract and display current " +"address of LocalHost");
System.out.println(address.getHostAddress()); |
The code in Listing 4 produces the output shown in Figure 4 .
| Figure 4 - Name and IP address of my localhost. |
|---|
Extract and display current name of LocalHost
dell8700Extract and display current address of LocalHost
192.168.2.16 |
But, we already knew the answer
Of course, we already knew what the output would be based on the toString output in Figure 3 . The difference is that in Figure 3 , we only have that information as part of something that is displayed on the screen. The code in Listing 4 gives us that same information in the form of String objects that we can use for some purpose other than simply looking at the information on the screen. (See googleAddress in Listing 6 for example.)
Canonical host name
The documentation describes the method named getCanonicalHostName partially as follows:
"Gets the fully qualified domain name for this IP address. Best effort method, meaning we may not be able to return the FQDN depending on the underlying system configuration."
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