ArrayList is a resizable-array of the list interface. It provides the methods that can be used to manipulate the size of the array whenever required.
Each instance of an ArrayList has some capacity, the capacity means the size to store the elements in the ArrayList. If you do not assign any capacity then the default capacity is 10, but if you enter the 11th element then it will automatically increase the capacity of the array as per your requirement since the ArrayList list is a growable list.
Some operations of ArrayList such as size(), isEmpty(), get(), set(), iterator(), and ListIterator() run in constant time. The add operation runs in n time, n is the number of times you are calling the add method or the number of times you are adding the element in the array.
Constructors of ArrayList:
- ArrayList() : Creates an empty ArrayList initially.
- ArrayList(Collection <? extends E> c) : Creates an ArrayList that contains the elements of the given collection.
Implementation of ArrayList API:
Java
// Java Program to Implement ArrayList API import java.util.ArrayList;import java.util.Arrays;import java.util.Collections;import java.util.Iterator;import java.util.List;import java.util.ListIterator;import java.util.Spliterator; public class ArrayListIntegerExample { public static void main(String[] args) { // Construct an ArrayList having default capacity 10 ArrayList<Integer> array = new ArrayList<>(); // ArrayList(Collection <? extends E> c) ArrayList<Integer> arrayWithColl = new ArrayList<Integer>(array); // Add elements in array array.add(100); array.add(120); array.add(500); array.add(220); array.add(150); // Insert the elements in specified index // array.add(index, element); array.add(4, 50); // Add all the elements together // array.addAll(collection) List<Integer> list; list = new ArrayList<Integer>(Arrays.asList(90, 20, 40, 10, 15)); array.addAll(list); // Add all the elements in specified index // array.addAll(index, collection) list = new ArrayList<Integer>(Arrays.asList(60, 25, 12, 16, 45)); array.addAll(2, list); // Create shallow copy of array ArrayList<Integer> array1; array1 = array; // Clear all the element from the list array.clear(); // Check whether the particular element is present // in the list or not array.contains(object) array1.add(100); array1.add(120); array1.add(500); array1.add(220); array1.add(150); System.out.println("Contains 120? : " + array1.contains(120)); // returns true System.out.println("Contains 200? : " + array1.contains(200)); // returns false // To ensure the minimum capacity of array // ArrayList<E> arrayname = new ArrayList<E>(int // minCapacity) ArrayList<Integer> array2 = new ArrayList<Integer>(10); // Iterate through the ArrayList System.out.println(); System.out.println("Elements of the array using enhanced for-loop : "); array.forEach(i -> System.out.print(i + " ")); System.out.println(); // Iterator System.out.println("Elements of the array using iterator : "); Iterator<Integer> itr = array.iterator(); while (itr.hasNext()) System.out.print(itr.next() + " "); System.out.println(); // List Iterator System.out.println("Elements of array using list - iterator : "); ListIterator<Integer> itr1 = array.listIterator(); while (itr1.hasNext()) System.out.print(itr1.next() + " "); System.out.println(); // Get the particular element from specified index // array.get(index) System.out.println("Element at index 2 is : " + array.get(2)); System.out.println(); // Get the position of particular element // array.indexOf(object) System.out.println("Element 500 is at index position : " + array.indexOf(500)); System.out.println(); // Check whether list is empty or not System.out.println("Array is empty? " + array.isEmpty()); System.out.println(); // Get the last index of element in array // array.lastIndexOf(object) System.out.println("Last index of the element 100 is : " + array.lastIndexOf(100)); System.out.println(); // Remove the particular element // array.remove(index) System.out.println("Remove the element which is at index 3 : " + array.remove(3)); System.out.println(); // Remove all the elements together // array.removeAll(collection) array.removeAll(array); // Remove all the elements of the collection // if condition specified the given predicate array1.add(100); array1.add(120); array1.add(500); array1.add(220); array1.add(150); array1.add(123); array1.add(233); array1.add(111); array1.removeIf(num -> (num % 3 == 0)); System.out.println("Array element after filtering : " + array1); System.out.println(); // Retain all the elements array1.retainAll(array); System.out.println("Retain the array element : " + array1); System.out.println(); // Set the element at particular index array1.set(3, 999); System.out.println(); // Display the size of arraylist System.out.println("Size of the array is : " + array1.size()); System.out.println(); // Sort the list Collections.sort(array1); System.out.println("Array elements after sorting : " + array1); System.out.println(); // Create a late-binding Spliterator<Integer> split = array1.spliterator(); // characteristic if (split.hasCharacteristics(Spliterator.ORDERED)) System.out.println("Ordered"); if (split.hasCharacteristics(Spliterator.SIZED)) System.out.println("Sized"); System.out.println(); // estimateSize() and getExactSizeIfKnown System.out.println("Estimate size of arraylist is : " + split.estimateSize()); System.out.println("Exact size of array is : " + split.getExactSizeIfKnown()); System.out.println(); // trySplit Spliterator<Integer> split1 = split.trySplit(); split.forEachRemaining(i -> System.out.println(i)); System.out.println("*****"); split1.forEachRemaining(i -> System.out.println(i)); System.out.println(); // Returns a sub-list within a specified index System.out.println("Sub-list from the index position 1 to 3 : " + array1.subList(1, 3)); System.out.println(); // Returns an array that contain all elements // public Object[] toArray() Object[] o = array1.toArray(); System.out.println("ArrayList traversal using toArray method : " + Arrays.toString(o)); System.out.println(); // public <T> T[] toArray(T[] a) Integer a[] = new Integer[array1.size()]; a = array1.toArray(a); System.out.println( "ArrayList traversal using toArray with argument method : " + Arrays.toString(a)); System.out.println(); // Trim the size to the number of elements array1.trimToSize(); System.out.println("Array size after trimming : " + array1.size()); }} |
Output
Contains 120? : true Contains 200? : false Elements of the array using enhanced for-loop : 100 120 500 220 150 Elements of the array using iterator : 100 120 500 220 150 Elements of array using list - iterator : 100 120 500 220 150 Element at index 2 is : 500 Element 500 is at index position : 2 Array is empty? false Last index of the element 100 is : 0 Remove the element which is at index 3 : 220 Array element after filtering : [100, 500, 220, 233] Retain the array element : [100, 500, 220, 233] Size of the array is : 4 Array elements after sorting : [100, 220, 500, 999] Ordered Sized Estimate size of arraylist is : 4 Exact size of array is : 4 500 999 ***** 100 220 Sub-list from the index position 1 to 3 : [220, 500] ArrayList traversal using toArray method : [100, 220, 500, 999] ArrayList traversal using toArray with argument method : [100, 220, 500, 999] Array size after trimming : 4
