Why am I getting java.util.ConcurrentModificationException?

Why am I getting java.util.ConcurrentModificationException?

As I run the following code :
import java.util.LinkedList;
class Tester {
public static void main(String args[]) {
LinkedList<String> list = new LinkedList<String>();
list.add(new String("suhail"));
list.add(new String("gupta"));
list.add(new String("ghazal"));
list.add(new String("poetry"));
list.add(new String("music"));
list.add(new String("art"));
try {
for(String s : list) {
list.add(0,"art");
list.remove(6);
System.out.println(list);
}
}catch(Exception exc) {
exc.printStackTrace();
}
}
}
I get an exception that says :
java.util.ConcurrentModificationException
at java.util.LinkedList$ListItr.checkForComodification(Unknown Source)
at java.util.LinkedList$ListItr.next(Unknown Source)
at Tester.main(Tester.java:14)
Why am I getting this exception ?