How to use Iterator in Java

// Demonstrate iterators. 
import java.util.*; 
class IteratorDemo { 
public static void main(String args[]) { 
// create an array list 
ArrayList al = new ArrayList(); 
// add elements to the array list 
al.add("C"); 
al.add("A"); 
al.add("E"); 
al.add("B"); 
al.add("D"); 
al.add("F"); 
// use iterator to display contents of al 
System.out.print("Original contents of al: "); 
Iterator itr = al.iterator(); 
while(itr.hasNext()) {

    Object element = itr.next(); 
    System.out.print(element + " ");

} 
System.out.println(); 
// modify objects being iterated 
ListIterator litr = al.listIterator(); 
while(litr.hasNext()) {

    Object element = litr.next(); 
    litr.set(element + "+");

} 
System.out.print("Modified contents of al: "); 
itr = al.iterator();
while(itr.hasNext()) {

    Object element = itr.next(); 
    System.out.print(element + " ");

} 
System.out.println(); 
// now, display the list backwards 
System.out.print("Modified list backwards: "); 
while(litr.hasPrevious()) {

    Object element = litr.previous(); 
    System.out.print(element + " ");

} 
System.out.println(); 
} 
}