Insertion order: It maintains the insertion order in Java. Null elements: Any number of null elements can be added to ArrayList.ĥ. Duplicate elements: Duplicate elements are allowed in the array list.Ĥ. Index-based structure: It uses an index-based structure in java.ģ. Once ArrayList is created, we can add any number of elements.Ģ. Resizable-array: ArrayList is a resizable array or growable array that means the size of ArrayList can increase or decrease in size at runtime. There are several features of ArrayList class in Java. It is a very common requirement for collection classes. The process of creating exactly duplicate objects is known as cloning. When the data or group of objects came from the network, the receiver will create duplicate objects. It is used to create exactly duplicate objects. A cloneable interface is present in java.lang package.Ģ. To provide support for this requirement, every collections class already implements Serializable and Cloneable.ġ. Usually, we use collections to hold and transfer objects from one place to another place. It helps in sending the data from one class to another class. A serializable interface is a marker interface that is used to send the group of objects over the network.

Therefore, if our frequent operation is retrieval operation then ArrayList is the best choice. Thus, Any random element we can access with the same or constant speed. Due to the implementation of random access interface, the 10th element and 1st crore element can also be accessed within 1 sec. Now assume that first element x can be accessed within only 1 sec. Assume that the first element is x, 10th element is y, and 1st crore element is z. For example, suppose there is a group of one crore objects in the array list. ArrayList class implements a random access interface so that we can access any random element at the same speed. RandomAccess interface is present in java.util package.ģ. It is introduced in Java 1.4 version for optimizing the list performance.Ģ. RandomAccess Interface is a marker interface that does not define any method or member.

It is also called an empty interface because of no field or methods. They are Random Access, Cloneable, and Serializable.Ī marker interface is an interface that does not have any methods or any member variables. The hierarchy diagram of ArrayList class in Java has shown in the below figure.Īs shown in the above hierarchy diagram, ArrayList class implements the List interface and extends AbstractList (Abstract class) which implements List interface.ĪrrayList class also implements 3 marker interfaces in Java. Hierarchy Diagram of ArrayList Class in Java When elements are removed from the list, the size of array list can be shrunk automatically but not capacity. The capacity of ArrayList does not shrink automatically. Java ArrayList uses a dynamic array internally for storing the group of elements, objects, or data. That is the first element will be placed at 0 index and the last element at index (n-1) where n is the size of ArrayList. It means that if the initial capacity of the array is exceeded, a new array with larger capacity is created automatically and all the elements from the current array are copied to the new array.Įlements in ArrayList are placed according to the zero-based index. It is dynamically created with an initial capacity. It was added to the Java programming in JDK 1.2 as part of the Java Collections Framework.ĪrrayList class is present in the java.util package and is commonly used for storing and manipulating collections of objects in an arbitrary order.Īn ArrayList is a resizable array that can grow or shrink in the memory whenever needed.

Java arraylist