Error while Creating collections with generic data type

I am trying to create different collections , add data and fetch it through Iterator.
I have jadk-1.7.0_55, and jre7 , I am using the below code ,but it showing error message saying remove arugumets(<String>) i.e it does not accept generic data. can anyone help me in this , how I can use generic data in Collections.

public class ArrayList {
public static void main(String args[]){

ArrayList<String> al=new ArrayList<String>();//creating arraylist
al.add("Ravi");//adding object in arraylist
al.add("Vijay");
al.add("Ravi");
al.add("Ajay");

Iterator itr=al.iterator();//getting Iterator from arraylist to traverse elements
while(itr.hasNext()){
System.out.println(itr.next());
}
}
}