Differences Between Enumeration And Iterator In Java

1) Introduction
Iterator interface is introduced from JDK 1.2 where as Enumeration interface is there from JDK 1.0.
2) remove() method
This is the main difference between Enumeration and Iterator interface. Enumeration only traverses the Collection object. You can’t do any modifications to Collection while traversing the Collection using Enumeration. Where as Iterator interface allows us to remove an element while traversing the Collection object. Iterator has remove() method which is not there in the Enumeration interface. Below is the list of Enumeration and Iteratormethods.
IteratorEnumeration
hasNext()hasMoreElements()
next()nextElement()
remove()(Not Available)
3) Legacy Interface
Enumeration is a legacy interface used to traverse only the legacy classes like Vector, HashTable and Stack. Where as Iterator is not a legacy code which is used to traverse most of the classes in the collection framework. For example, ArrayList, LinkedList, HashSet, LinkedHashSet, TreeSet, HashMap, LinkedHashMap, TreeMap etc.
4) Fail-Fast Vs Fail-Safe
Iterator is a fail-fast in nature. i.e it throws ConcurrentModificationException if a collection is modified while iterating other than it’s own remove() method. Where as Enumeration is fail-safe in nature. It doesn’t throw any exceptions if a collection is modified while iterating. [See more]
5) Safe And Secure
As Iterator is fail-fast in nature and doesn’t allow modification of a collection by other threads while iterating, it is considered as safe and secure than Enumeration.
6) Which One To Use
According to Java API Docs, Iterator is always preferred over the Enumeration. Here is the note from the Enumeration Docs.

Enumeration Vs Iterator In Java :

EnumerationIterator
Using Enumeration, you can only traverse the collection. You can’t do any modifications to collection while traversing it.Using Iterator, you can remove an element of the collection while traversing it.
Enumeration is introduced in JDK 1.0Iterator is introduced from JDK 1.2
Enumeration is used to traverse the legacy classes like Vector, Stack and HashTable.Iterator is used to iterate most of the classes in the collection framework like ArrayList, HashSet, HashMap, LinkedList etc.
Methods : hasMoreElements() and nextElement()Methods : hasNext(), next() and remove()
Enumeration is fail-safe in nature.Iterator is fail-fast in nature.
Enumeration is not safe and secured due to it’s fail-safe nature.Iterator is safer and secured than Enumeration.

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