Why arraylist is used in java

Keep Exploring. Related Courses. Learn in-demand tech skills in half the time. Early Access Courses. Assessments New. Free Trial New. For Business. For Educators. Become an Affiliate. Terms of Service. Throws NullPointerException, if the specified collection is null. Inserts all of the elements in the specified collection into this list, starting at the specified position. Throws NullPointerException if the specified collection is null. Returns true if this list contains the specified element.

Increases the capacity of this ArrayList instance, if necessary, to ensure that it can hold at least the number of elements specified by the minimum capacity argument.

Returns the element at the specified position in this list. Returns the index in this list of the first occurrence of the specified element, or -1 if the List does not contain this element. Returns the index in this list of the last occurrence of the specified element, or -1 if the list does not contain this element. Removes the element at the specified position in this list. Removes from this List all of the elements whose index is between fromIndex, inclusive and toIndex, exclusive.

Replaces the element at the specified position in this list with the specified element. Returns an array containing all of the elements in this list in the correct order.

Throws NullPointerException if the specified array is null. It grows its size to accommodate new elements and shrinks the size when the elements are removed.

ArrayList internally uses an array to store the elements. Just like arrays, It allows you to retrieve the elements by their index. You cannot create an ArrayList of primitive types like int , char etc. You need to use boxed types like Integer , Character , Boolean etc. Java ArrayList is not synchronized.

If multiple threads try to modify an ArrayList at the same time, then the final outcome will be non-deterministic. You must explicitly synchronize access to an ArrayList if multiple threads are gonna modify it. How to add all the elements from an existing collection to the new ArrayList using the addAll method.

How to remove the element at a given index in an ArrayList remove int index. How to remove an element from an ArrayList remove Object o. How to remove all the elements from an ArrayList that exist in a given collection removeAll. How to remove all the elements matching a given predicate removeIf.

How to clear an ArrayList clear. The iterator and listIterator methods are useful when you need to modify the ArrayList while traversing. Consider the following example, where we remove elements from the ArrayList using iterator. Check if an ArrayList contains a given element contains. Find the index of the first occurrence of an element in an ArrayList indexOf.

Find the index of the last occurrence of an element in an ArrayList lastIndexOf.