What is iterator Why do we need 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 iterator Java?
An iterator is an object that has methods that allow you to proccess a collection of items one at a time. The java. … Iterator interface provides the following methods: boolean hasNext() – Returns true if the iteration has more elements. E next() – Returns the next element in the iteration.
Is iterator necessary?
5 Answers. As you have stated iterator is used when you want to remove stuff whilst you iterate over the array contents. If you don’t use an iterator but simply have a for loop and inside it use the remove method you will get exceptions because the contents of the array changes while you iterate through.
Where do we use iterator?
An Iterator is an object that can be used to loop through collections, like ArrayList and HashSet. It is called an “iterator” because “iterating” is the technical term for looping. To use an Iterator, you must import it from the java. util package.
Which for loop is faster in Java?
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.
What is hasNext () in Java?
The hasNext() is a method of Java Scanner class which returns true if this scanner has another token in its input.
Why iterator has remove method?
2 Answers. So it checks for concurrent modifications, removes element using public ArrayList remove method, and increments counter of list modifications so ConcurrentModificationException won’t be thrown at next iteration.
What is entrySet in Java?
entrySet() method in Java is used to create a set out of the same elements contained in the hash map. It basically returns a set view of the hash map or we can create a new set and store the map elements into them. Syntax: hash_map.entrySet()
Is iterator faster than for loop C++?
Iterating over a vector using iterators is not faster and is not safer (actually if the vector is possibly resized during the iteration using iterators will put you in big troubles). The idea of having a generic loop that works when you will change later the container type is also mostly nonsense in real cases.
Is iterator an abstract class?
Iterator is an interface. It is not a class. It is used to iterate through each and every element in a list. Iterator is implemented Iterator design pattern.
What is difference between for and foreach in Java?
The key difference between for Loop and foreach loop is that the for loop is a general purpose control structure while the foreach loop is an enhanced for loop that is applicable only to arrays and collections.