java socket programming check domain is true or not error

I'm reading domains from a file and check whether the domain format is correct or not. if domain is correct write it to true.txt and if not, write it to wrong.txt. My problem is that the program after reading some domains from file throws an exception. I've attached my code and errors below:

/********************************************************************************************/
BufferedReader br = null;
FileWriter fw=null;
FileWriter ft=null;
String strLine = "";
try {
br = new BufferedReader( new FileReader("test.txt"));
fw= new  FileWriter("wrongfile.txt");
ft= new  FileWriter("truefile.txt");
while( (strLine = br.readLine()) != null){
System.out.println(strLine);
URL u = new URL ("http://"+strLine);
HttpURLConnection huc =  ( HttpURLConnection )  u.openConnection (); 
huc.setRequestMethod ("GET");  
huc.setRequestMethod ("HEAD"); 
huc.connect();
int coded = huc.getResponseCode() ;
System.out.println("code:"+coded);
int  code=coded/100;
if(code==3||code==4||code==5)
{
fw.write(strLine+":error:"+coded+"\n");
System.out.println("domain is not ok:"+coded);
}
else
{
ft.write(strLine+"\n");
System.out.println("domain is ok:");
}
}
} catch (FileNotFoundException e) {
System.err.println("File not found");
} 
br.close();
fw.close();
ft.close();
}

here is error portion:

           Exception in thread "main" java.net.UnknownHostException: bushido.academy
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at java.net.Socket.connect(Socket.java:538)
at sun.net.NetworkClient.doConnect(NetworkClient.java:180)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:432)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:527)
at sun.net.www.http.HttpClient.<init>(HttpClient.java:211)
at sun.net.www.http.HttpClient.New(HttpClient.java:308)
at sun.net.www.http.HttpClient.New(HttpClient.java:326)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1202)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1138)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1032)
at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:966)
at checker.Urlchecker.main(Urlchecker.java:50)
C:\Users\Imran\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1

   public static void main(String[] args) throws IOException {
int coded = 0;
int counter=0;
int num=10;
Scanner in = new Scanner(System.in);
System.out.print("Enter the file name:");
String filename=in.nextLine();
BufferedReader br = null;
FileWriter fw=null;
FileWriter ft=null;
String f="truefile.txt";
String strLine = "";
br = new BufferedReader( new FileReader(filename));
fw= new  FileWriter("wrongfile.txt");
ft= new  FileWriter(f);
while( (strLine = br.readLine()) != null){
try {
System.out.println(strLine);
URL u = new URL ("http://"+strLine);
HttpURLConnection huc =  ( HttpURLConnection )  
u.openConnection () ; 
//huc.setRequestMethod ("GET");  
huc.setRequestMethod ("HEAD");
coded = huc.getResponseCode() ;
int  code=coded/100;
if(code==4 || code==5 || coded==303)
{
fw.write(strLine+":error:"+coded+"\n"+"\n");
System.out.println("domain is not ok error:"+coded);
}
else
{
ft.write(strLine+"\n"+"\n");
System.out.println("domain is ok:");
}
counter++;
System.out.println("total domain checked:"+counter);
} 
catch (FileNotFoundException e) {
System.err.println("File not found");
}
catch (IOException e) {
System.out.println("domain not exist fatal error");
}
catch(InterruptedException e)
{
System.out.println("timeout");
}
}
br.close();
ft.close();
fw.close();
}
}