Iterator and Enumeration both are the cursors to traverse and access an element from the collection. They both belong to the collection framework. Enumeration was added in JDK1.0 and Iterator in the JDK.1.2 version in the collection framework.
Enumeration can’t make structural changes in the collection because it has read-only access to the element in the collection. It has the following methods :
- *hasMoreElements()
- *nextElement()
On the other hand, an iterator can read and remove the element in the collection. It has the following methods −
- *hasNext()
- *next()
- *remove()
| Sr. No. | Key | Iterator | Enumeration |
|---|---|---|---|
| 1 | Basic | In Iterator, we can read and remove element while traversing element in the collections. | Using Enumeration, we can only read element during traversing element in the collections. |
| 2. | Access | It can be used with any class of the collection framework. | It can be used only with legacy class of the collection framework such as a Vector and HashTable. |
| 3. | Fail-Fast and Fail -Safe | Any changes in the collection, such as removing element from the collection during a thread is iterating collection then it throw concurrent modification exception. | Enumeration is Fail safe in nature. It doesn’t throw concurrent modification exception |
| 4. | Limitation | Only forward direction iterating is possible | Remove operations can not be performed using Enumeration. |
| 5. | Methods | It has following methods − *hasNext() *next() *remove() | It has following methods − *hasMoreElements() *nextElement() |
Example of Enumeration
class EnumerationExample {
public static void main(String args[]) {
List list = new ArrayList(Arrays.asList( new String[] {"Apple", "Cat", "Dog", "Rat"}));
Vector v = new Vector(list);
delete(v, "Dog");
}
private static void delete(Vector v, String name) {
Enumeration e = v.elements();
while (e.hasMoreElements()) {
String s = (String) e.nextElement();
if (s.equals(name)) {
v.remove(name);
}
}
// Display the names
System.out.println("The names are:");
e = v.elements();
while (e.hasMoreElements()) {
// Prints elements
System.out.println(e.nextElement());
}
}
}Example of Iterator
class IteratorExample {
public static void main(String args[]) {
List list = new ArrayList(Arrays.asList( new String[] {"Apple", "Cat", "Dog", "Rat"}));
Vector v = new Vector(list);
delete(v, "Dog");
}
private static void delete(Vector v, String name) {
Iterator i = v.iterator();
while (i.hasNext()) {
String s = (String) i.next();
if (s.equals(name)) {
i.remove();
}
}
// Display the names
System.out.println("The names are:");
i = v.iterator();
while (i.hasNext()) {
System.out.println(i.next());
}
}
}