What is Arraylist?
Java ArrayList class uses a dynamic array for storing the elements. It is like an array, but there is no size limit. We can add or remove elements anytime. So, it is much more flexible than the traditional array. It is found in the java.util package. The ArrayList in Java can have the duplicate elements also. It implements the List interface so we can use all the methods of the List interface here. The ArrayList maintains the insertion order internally.
import java.util.ArrayList;
import java.util.Collections;
public class ArrayListMethods {
public static void main(String[] args) {
// 1. CREATE ArrayList
ArrayList<String> list = new ArrayList<>();
System.out.println("Created ArrayList: " + list);
// 2. add() - Add elements
list.add("Chennai");
list.add("Mumbai");
list.add("Delhi");
list.add("Kolkata");
System.out.println("\nAfter add() : " + list);
// Output: [Chennai, Mumbai, Delhi, Kolkata]
// 3. add(index, element) - Add at position
list.add(2, "Bangalore");
System.out.println("After add(2) : " + list);
// Output: [Chennai, Mumbai, Bangalore, Delhi, Kolkata]
// 4. get() - Get element by index
String city = list.get(0);
System.out.println("\nget(0) : " + city);
// Output: Chennai
// 5. set() - Update element
list.set(1, "Hyderabad");
System.out.println("After set(1) : " + list);
// Output: [Chennai, Hyderabad, Bangalore, Delhi, Kolkata]
// 6. remove(index) - Remove by index
list.remove(3);
System.out.println("After remove(3) : " + list);
// Output: [Chennai, Hyderabad, Bangalore, Kolkata]
// 7. remove(object) - Remove by value
list.remove("Kolkata");
System.out.println("After remove() : " + list);
// Output: [Chennai, Hyderabad, Bangalore]
// 8. size() - Get size
System.out.println("\nsize() : " + list.size());
// Output: 3
// 9. contains() - Check element exists
System.out.println("contains Chennai: " + list.contains("Chennai"));
// Output: true
System.out.println("contains Delhi : " + list.contains("Delhi"));
// Output: false
// 10. indexOf() - Get index of element
System.out.println("\nindexOf Chennai : " + list.indexOf("Chennai"));
// Output: 0
// 11. isEmpty() - Check if empty
System.out.println("isEmpty() : " + list.isEmpty());
// Output: false
// 12. sort() - Sort elements
Collections.sort(list);
System.out.println("\nAfter sort() : " + list);
// Output: [Bangalore, Chennai, Hyderabad]
// 13. reverse() - Reverse elements
Collections.reverse(list);
System.out.println("After reverse() : " + list);
// Output: [Hyderabad, Chennai, Bangalore]
// 14. subList() - Get portion of list
list.add("Delhi");
list.add("Mumbai");
System.out.println("\nFull list : " + list);
System.out.println("subList(1,3) : " + list.subList(1, 3));
// Output: [Chennai, Bangalore]
// 15. toArray() - Convert to Array
Object[] arr = list.toArray();
System.out.println("\ntoArray() : ");
for (Object obj : arr) {
System.out.println(" " + obj);
}
// 16. addAll() - Add multiple elements
ArrayList<String> newCities = new ArrayList<>();
newCities.add("Pune");
newCities.add("Jaipur");
list.addAll(newCities);
System.out.println("\nAfter addAll() : " + list);
// Output: [Hyderabad, Chennai, Bangalore, Delhi, Mumbai, Pune, Jaipur]
// 17. clear() - Remove all elements
list.clear();
System.out.println("After clear() : " + list);
// Output: []
System.out.println("isEmpty() : " + list.isEmpty());
// Output: true
}
}
