Programming Forums > Application Development > Java

fresher · Jan 11th, 2007, 12:58 PM

Hi all, i've this code below which prompts a user to select from a list of ip addresses.e.g 192.168.2.1....etc. Now i wona modify this code so that if the machine on which the program is run has a different network part (192.168.2.) then I can prompt the user to enter their network ID e.g (148.145.23.) then increment the last bit using a for loop. Anyone able to help me out pls? thanks in advance

I have added this block of code below in order to do this but it doesnt work:

(Toggle Plain Text)

System.out.print("Enter your network part or hit enter to proceed: ");
            String network = in.readString();
            
            //test
            System.out.println(network);
            
            //if enter is pressed - same network
            if (network == null)
        
            {
            
            System.out.print("SELECT A MACHINE TO VIEW FROM LIST: ");
            int choice = in.readInteger();
            }

            else
            {
                //pass new network part to ip string variable
                ip = network;
            }

nb: this code is part of my previous post on ' passing a string to a variable.....' click here to view full code:http://www.programmingforums.org/for...-variable.html
any help appreciated.

Arevos · Jan 11th, 2007, 1:30 PM

Possibly:

(Toggle Plain Text)

if ("".equals(network))

Or perhaps:

(Toggle Plain Text)

if ("".equals(network.trim()))

fresher · Jan 11th, 2007, 1:43 PM

Quote:

Originally Posted by Arevos

Possibly:

(Toggle Plain Text)

if ("".equals(network))

Or perhaps:

(Toggle Plain Text)

if ("".equals(network.trim()))

thanks for your reply but is network.trim() a java function and what is the meaning of " ".equals..... please? a little comment will be perfect. thanks in advance

Arevos · Jan 11th, 2007, 1:57 PM

Quote:

Originally Posted by fresher

thanks for your reply but is network.trim() a java function

Yes, and a quick Google or a look at the Sun javadocs would tell you all about it

Quote:

Originally Posted by fresher

and what is the meaning of " ".equals..... please? a little comment will be perfect. thanks in advance

To check whether two strings, a and b, are equal, you'd use the following code:

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a.equals(b)

If b is null, then the above expression returns false. If a is null, then an exception is raised, because you can't have null.equals(b).

So when comparing a string whose value could possibly be null (i.e. network), against a string whose value cannot be null (i.e. ""), then it's best to have the string that cannot be null as the one on the left, and the string that can be null on the right.

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"".equals(stringThatMightBeNull)    // false when null

stringThatMightBeNull.equals("")    // error when null

fresher · Jan 11th, 2007, 1:59 PM

Also Arevos the 'if (" ".equals(network))' works if enter is pressed but the else part doesnt work if a network address is entered. In otherwords when the network part is entered, the switch statement is not executed. pls help me out. thanks in advance

Jan 11th, 2007, 12:58 PM	#1
fresher Newbie Join Date: Dec 2006 Posts: 13 Rep Power: 0	accepting user input Hi all, i've this code below which prompts a user to select from a list of ip addresses.e.g 192.168.2.1....etc. Now i wona modify this code so that if the machine on which the program is run has a different network part (192.168.2.) then I can prompt the user to enter their network ID e.g (148.145.23.) then increment the last bit using a for loop. Anyone able to help me out pls? thanks in advance I have added this block of code below in order to do this but it doesnt work: (Toggle Plain Text) System.out.print("Enter your network part or hit enter to proceed: "); String network = in.readString(); //test System.out.println(network); //if enter is pressed - same network if (network == null) { System.out.print("SELECT A MACHINE TO VIEW FROM LIST: "); int choice = in.readInteger(); } else { //pass new network part to ip string variable ip = network; } System.out.print("Enter your network part or hit enter to proceed: "); String network = in.readString(); //test System.out.println(network); //if enter is pressed - same network if (network == null) { System.out.print("SELECT A MACHINE TO VIEW FROM LIST: "); int choice = in.readInteger(); } else { //pass new network part to ip string variable ip = network; } nb: this code is part of my previous post on ' passing a string to a variable.....' click here to view full code:http://www.programmingforums.org/for...-variable.html any help appreciated.

Jan 11th, 2007, 1:30 PM	#2
Arevos Programming Guru Join Date: Aug 2005 Location: England Posts: 1,499 Rep Power: 5	Possibly: (Toggle Plain Text) if ("".equals(network)) if ("".equals(network)) Or perhaps: (Toggle Plain Text) if ("".equals(network.trim())) if ("".equals(network.trim()))

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Jan 11th, 2007, 1:59 PM	#5
fresher Newbie Join Date: Dec 2006 Posts: 13 Rep Power: 0	Also Arevos the 'if (" ".equals(network))' works if enter is pressed but the else part doesnt work if a network address is entered. In otherwords when the network part is entered, the switch statement is not executed. pls help me out. thanks in advance

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Programming Forums > Application Development > Java

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