Re: Error Message: Exception in thread "main" java.lang.NullPointerException etc.

[viki.khatri]

help me to solve this error: -

import java.io.IOException;

import java.net.InetAddress;

import java.net.NetworkInterface;

import java.net.URLConnection;
import java.net.UnknownHostException;
import java.net.*;


public class IsReachable
{


public static void main(final String[] args) throws IOException
{

InetAddress host;
try
{


for (int i = 1; i < 255; i++)
{

host = InetAddress.getByName("192.168.6." + i);

NetworkInterface network = NetworkInterface.getByInetAddress(host);

byte[] mac = new byte[100];
mac=network.getHardwareAddress();


StringBuilder sb = new StringBuilder();


for (int j = 0; j < mac.length; j++)
{

sb.append(String.format("%02X%s", mac[j], (j < mac.length - 1) ? "-" : ""));

}


if (host.isReachable(10000))
{

System.out.println("Connected " + host + " " + sb.toString());

}
else
{

System.out.println("Failed " + host);

}

}

}
catch (UnknownHostException e) {


e.printStackTrace();


}
catch (SocketException e) {


e.printStackTrace();

}

}

}

____________Output______________


C:\Program Files\Java\jdk1.6.0_05\bin>javac IsReachable.java

C:\Program Files\Java\jdk1.6.0_05\bin>java IsReachable
Exception in thread "main" java.lang.NullPointerException
at IsReachable.main(IsReachable.java:32)

thank u

[Norm]

Exception in thread "main" java.lang.NullPointerException
at IsReachable.main(IsReachable.java:32)

Look at line 32 in the your source and see what variable is null. Then backtrack in the code to see why that variable does not have a valid value.
If you can not tell which variable it is, add a println just before line 32 and print out the values of all the varibles on that line.

Please edit your post and wrap your code with
[code=java]
<YOUR CODE HERE>
[/code]
to get highlighting and preserve formatting.