Filtering returned results

[eohalloran]

Hi,

I have added a small piece of code that goes out and discovers what ethernet ports are available on a PC and returns them to the calling function in a GUI that populates a Combo Box. The code is as follows:

import java.net.*;
import java.net.SocketException;
import java.util.*;


public class ListNets
{
       String tmp2[];
       public static String[] ListEthPorts ()
       {
          String tmp[] = {"1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12"};
          int i = 0;
          try
          {
             Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces();
             for (NetworkInterface netint : Collections.list(nets))
             {
                tmp[i] = netint.getName();
                i++;
             }

          }
          catch(SocketException exp)
          {

          }
          return tmp;
    }
}

This works great and does actually populate the combo box with the correct interface names. What I want to do now is apply a filter based on a regular expression that only returns interface names of a specific type such as eth1.34, eth1.35 etc.... Currently it returns all interfaces such as l0, vif 1.1.

The regular expression I want to apply is:

"(eth[0-9]\\.[0-9]{2})|(eth[0-9])|(eth[0-9]{2})|(eth[0-9]{2}\\.[0-9])|(eth[0-9]{2}\\.[0-9]{2})"

Is there a neat way of doing this just before tmp is returned? I have tried some examples that are out there but they have not worked for me. Also is there a neater way to initialize the 12 ports instead of the way I have done it with the String tmp[]?

Thanks

Eric

BTW, I am a complete newb at Java, so forgive my ignorance in advance.

[Norm]

What contents do you need in the tmp array? The code replaces the first n values.

[eohalloran]

Hi Norm,

Each PC I am running the GUI on has a combination of real, virtual and sub-interfaces. I have VLAN trunking setup and the GUI I want to run only on the sub-interfaces that connect to the VLan'd switch. Basically there are 12 interfaces and that code returns the following for example on one PC:

"vif0, peth0, eth1, eth1.35, eth1.34, eth1.33, eth1.32, eth1.31, eth1.30, eth0, virbr0, l0"

I only want to return "eth1.35, eth1.34, eth1.33, eth1.32, eth1.31, eth1.30"

The regular expression I constructed above will work but I can't figure how to apply it. I can get the required results by indexing the results but that means if I add or remove sub-interfaces, I have to alter the code. The best way is to filter using the regular expression.

Thanks

[Norm]

Is there a forum for regular expressions?

[Shoss]

Take a look here for regular expressions in java. Basically, i think you'd just want to throw an if statement around where you assign the name to the string array and check the string with the .matches() function.

if (netint.getName().matches(".*")) {
  ...add to array...
}

Also, instead of using a string array whose length has to be defined, i would suggest looking at an ArrayList. ArrayLists are dynamic so you can add as many values as you want whenever you need to.

[eohalloran]

Shoss,

Thanks for the pointer to ArrayLists. I applied the following code and it works as expected.

import java.lang.String.*;
import java.net.*;
import java.net.SocketException;
import java.util.*;
import java.util.ArrayList.*;
import java.util.regex.Pattern;


public class ListNets
{
       public static String[] ListEthPorts ()
       {
          String [] tmp = null;
          String ifName = null;
          ArrayList<String> ifList = new ArrayList<String>();
          try
          {
             Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces();
             for (NetworkInterface netint : Collections.list(nets))
             {
                ifName = netint.getName();
                if(Pattern.matches("(eth[0-9]\\.[0-9]{2})|(eth[0-9]{2}\\.[0-9])|(eth[0-9]{2}\\.[0-9]{2})", ifName) == true)
                {
                   ifList.add(ifName);
                }
             }

	     int numValidIf = ifList.size();
             tmp = new String[numValidIf];

             for(int i = 0; i < numValidIf; i++)
             {
                tmp[i] = ifList.get(i);
             }
          }

          catch(SocketException exp)
          {

          }
          return tmp;
    }
}

Eric