Constructors in ArrayList in Java

What is ArrayList in Java?

ArrayList is a Java class implemented using the List interface. Java ArrayList, as the name suggests, provides the functionality of a dynamic array where the size is not fixed as an array. Also, as a part of the Collections framework, it has many features not available with arrays....

Java ArrayList Example

Example 1: The following implementation demonstrates how to create and use an ArrayList with a mention of its size....

Important Features of ArrayList in Java

ArrayList inherits AbstractList class and implements the List interface.ArrayList is initialized by size. However, the size is increased automatically if the collection grows or shrinks if the objects are removed from the collection.Java ArrayList allows us to randomly access the list.ArrayList can not be used for primitive types, like int, char, etc. We need a wrapper class for such cases.ArrayList in Java can be seen as a vector in C++.ArrayList is not Synchronized. Its equivalent synchronized class in Java is Vector....

Constructors in ArrayList in Java

In order to Create an ArrayList, we need to create an object of the ArrayList class. The ArrayList class consists of various constructors which allow the possible creation of the array list. The following are the constructors available in this class:...

Java ArrayList Methods

MethodDescriptionadd(int index, Object element)This method is used to insert a specific element at a specific position index in a list.add(Object o)This method is used to append a specific element to the end of a list.addAll(Collection C)This method is used to append all the elements from a specific collection to the end of the mentioned list, in such an order that the values are returned by the specified collection’s iterator.addAll(int index, Collection C)Used to insert all of the elements starting at the specified position from a specific collection into the mentioned list.clear()This method is used to remove all the elements from any list.clone()This method is used to return a shallow copy of an ArrayList in Java.contains? (Object o)Returns true if this list contains the specified element.ensureCapacity?(int minCapacity)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.forEach?(Consumer action)Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.get?(int index)Returns the element at the specified position in this list.indexOf(Object O)The index the first occurrence of a specific element is either returned or -1 in case the element is not in the list.isEmpty?()Returns true if this list contains no elements.lastIndexOf(Object O)The index of the last occurrence of a specific element is either returned or -1 in case the element is not in the list.listIterator?()Returns a list iterator over the elements in this list (in proper sequence).listIterator?(int index)Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list.remove?(int index)Removes the element at the specified position in this list.remove? (Object o)Removes the first occurrence of the specified element from this list, if it is present.removeAll?(Collection c)Removes from this list all of its elements that are contained in the specified collection.removeIf?(Predicate filter)Removes all of the elements of this collection that satisfy the given predicate.removeRange?(int fromIndex, int toIndex)Removes from this list all of the elements whose index is between fromIndex, inclusive, and toIndex, exclusive.retainAll?(Collection c)Retains only the elements in this list that are contained in the specified collection.set?(int index, E element)Replaces the element at the specified position in this list with the specified element.size?()Returns the number of elements in this list.spliterator?()Creates a late-binding and fail-fast Spliterator over the elements in this list.subList?(int fromIndex, int toIndex)Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive.toArray()This method is used to return an array containing all of the elements in the list in the correct order.toArray(Object[] O)It is also used to return an array containing all of the elements in this list in the correct order same as the previous method.trimToSize()This method is used to trim the capacity of the instance of the ArrayList to the list’s current size....

Operations performed in ArrayList

1. Adding Elements...

Complexity of Java ArrayList

Operation Time Complexity Space Complexity Inserting Element in ArrayList O(1) O(N) Removing Element from ArrayList O(N) O(1) Traversing Elements in ArrayList O(N) O(N) Replacing Elements in ArrayList O(1) O(1)...

Advantages of Java ArrayList

Dynamic size: ArrayList can dynamically grow and shrink in size, making it easy to add or remove elements as needed.Easy to use: ArrayList is simple to use, making it a popular choice for many Java developers.Fast access: ArrayList provides fast access to elements, as it is implemented as an array under the hood.Ordered collection: ArrayList preserves the order of elements, allowing you to access elements in the order they were added.Supports null values: ArrayList can store null values, making it useful in cases where the absence of a value needs to be represented....

Disadvantages of Java ArrayList

Slower than arrays: ArrayList is slower than arrays for certain operations, such as inserting elements in the middle of the list.Increased memory usage: ArrayList requires more memory than arrays, as it needs to maintain its dynamic size and handle resizing.Not thread-safe: ArrayList is not thread-safe, meaning that multiple threads may access and modify the list concurrently, leading to potential race conditions and data corruption.Performance degradation: ArrayList’s performance may degrade as the number of elements in the list increases, especially for operations such as searching for elements or inserting elements in the middle of the list....

Conclusion

Points to be remembered from this article are mentioned below:...

FAQs of ArrayList

What is an ArrayList in Java?...