What Is The Difference Between Iterator And Enumeration?

Which is faster enumeration or iterator?

Iterator can remove the element during traversal of collection as it has remove() method.

Enumeration does not have remove() method.

Iterator is fail-fast in nature.

It throws ConcurrentModificationException if a Collection is modified while iterating other than its own remove() method..

Can we add constants to enum without breaking existing code?

Enum is type-safe, you cannot assign anything else other than predefined Enum constants to an Enum variable. … You can use Enum inside Java Switch statement. You can add new constants to enum without breaking existing code.

Why enumeration is fail safe?

3. Fail-fast or Fail-safe : Enumeration is fail-safe in nature. It does not throw ConcurrentModificationException if Collection is modified during the traversal. … It throws ConcurrentModificationException if a Collection is modified while iterating other than its own remove() method.

Which collection is faster in Java?

If you need fast access to elements using index, ArrayList should be choice. If you need fast access to elements using a key, use HashMap. If you need fast add and removal of elements, use LinkedList (but it has a very poor seeking performance).

Which is better list or set?

The difference is that Set is stored in unordered way and does not allow duplicate values. List is used to store elements in ordered way and it does allow duplicate values. Set elements cannot be accessed by an index position, and List elements can be accessed with an index position.

Is iterator Fail Safe?

The major difference is fail-safe iterator doesn’t throw any Exception, contrary to fail-fast Iterator. This is because they work on a clone of Collection instead of the original collection and that’s why they are called as the fail-safe iterator.

What is the purpose of an iterator?

The primary purpose of an iterator is to allow a user to process every element of a container while isolating the user from the internal structure of the container. This allows the container to store elements in any manner it wishes while allowing the user to treat it as if it were a simple sequence or list.

What is an example of collection?

The definition of a collection is a group of things or people gathered together. An example of a collection is someone gathering together five hundred baseball cards.

Is enum serializable in Java?

Because enums are automatically Serializable (see Javadoc API documentation for Enum), there is no need to explicitly add the “implements Serializable” clause following the enum declaration. Once this is removed, the import statement for the java. io. Serializable interface can also be removed.

Does ArrayList maintain insertion order?

ArrayList maintains the insertion order i.e order of the object in which they are inserted. HashSet is an unordered collection and doesn’t maintain any order. ArrayList allows duplicate values in its collection. On other hand duplicate elements are not allowed in Hashset.

Which is faster set or list in Java?

Sets are faster than Lists if you have a large data set, while the inverse is true for smaller data sets.

Can we extend enums in Java?

Java enum is a kind of a compiler magic. In byte code, any enum is represented as a class that extends the abstract class java. … Therefore, enum cannot extend any other class or enum : there is no multiple inheritance. Class cannot extend enum , as well.

Why iterator is fail fast?

Fail-Fast iterators immediately throw ConcurrentModificationException if a collection is modified while iterating over it. Where as Fail-Safe iterators don’t throw any exceptions if a collection is modified while iterating over it. Because, they operate on the clone of the collection, not on the actual collection.

Why enumeration is faster than iterator?

In the example of the micro-benchmark given, the reason the Enumeration is faster than Iterator is because it is tested first. 😉 The longer answer is that the HotSpot compiler optimises a whole method when a loop has iterated 10,000 times.

What is difference between list and set?

List Vs Set. 1) List is an ordered collection it maintains the insertion order, which means upon displaying the list content it will display the elements in the same order in which they got inserted into the list. Set is an unordered collection, it doesn’t maintain any order.

What is the difference between collection and collections?

The differences between the Collection and Collections are given below. The Collection is an interface whereas Collections is a class. The Collection interface provides the standard functionality of data structure to List, Set, and Queue. However, Collections class is to sort and synchronize the collection elements.

Which list is faster in Java?

get(int index) in ArrayList gives the performance of O(1) while LinkedList performance is O(n) . Reason: ArrayList maintains index based system for its elements as it uses array data structure implicitly which makes it faster for searching an element in the list.

Are enums type safe?

The enums are type-safe means that an enum has its own namespace, we can’t assign any other value other than specified in enum constants. … Additionally, an enum is a reference type, which means that it behaves more like a class or an interface.

Is iterator faster than for loop?

Iterator and for-each loop are faster than simple for loop for collections with no random access, while in collections which allows random access there is no performance change with for-each loop/for loop/iterator.

Is iterator an abstract class?

Each implementation of Iterator is unique to the collection it is iterating. These is not enough common code to warrant an abstract base class. … This combination allows for complete freedom to implement the interface but allows for code reuse in the cases where implementations can use the abstract class.

Does iterator maintain order?

For instance, an iterator obtained from a List will iterate through the elements of that List in the same order the elements are stored internally in the List . An Iterator obtained from a Set , on the other hand, does not make any guarantees about the exact sequence the elements in the Set are iterated in.