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ArrayList in Java is most frequently used collection class after HashMap in Java. Java ArrayList represents an automatic re-sizeable array and used in place of the array. Since we can not modify the size of an array after creating it, we prefer to use ArrayList in Java which re-size itself automatically once it gets full. ArrayList in Java implements List interface and allow null. Java ArrayList also maintains insertion order of elements and allows duplicates opposite to any Set implementation which doesn't allow duplicates. ArrayList supports both Iterator and ListIterator for iteration but it’s recommended to use ListIterator as it allows the programmer to traverse the list in either direction, modify the list during iteration, and obtain the Iterator's current position in the list. But while using ListIterator you need to be little careful because ListIterator has no current element; its cursor position always lies between the element that would be returned by a call to previous() and the element that would be returned by a call to next(). In this Java ArrayList tutorial, we will see how to create Java ArrayList and perform various operations on Java ArrayList. This collection class is also favorited on many core Java interviews with questions like Difference between ArrayList and Vector or LinkedList vs ArrayList.