Java ArrayList Methods

Lecture 69:-  Java ArrayList Methods

ArrayList in Java provides a wide range of methods to manipulate the list of elements it holds. Here are some of the commonly used methods of the ArrayList class:

1. Adding Elements:

   • add(E element): Appends the specified element to the end of the list.
   • add(int index, E element): Inserts the specified element at the specified position in the list.

2. Accessing Elements:

   • get(int index): Returns the element at the specified index.
   • set(int index, E element): Replaces the element at the specified index with the specified element.

3. Removing Elements:

   • remove(int index): Removes the element at the specified index from the list.
   • remove(Object o): Removes the first occurrence of the specified element from the list.
   • clear(): Removes all elements from the list.

4. Size and Checking Empty:

   • size(): Returns the number of elements in the list.
   • isEmpty(): Returns true if the list is empty, otherwise false.

5. Searching Elements:

   • contains(Object o): Returns true if the list contains the specified element, otherwise false.
   • indexOf(Object o): Returns the index of the first occurrence of the specified element, or -1 if not found.
   • lastIndexOf(Object o): Returns the index of the last occurrence of the specified element, or -1 if not found.

6. Sublist Operations:

   • subList(int fromIndex, int toIndex): Returns a new ArrayList containing elements from fromIndex (inclusive) to toIndex (exclusive).

7. Converting to Array:

   • toArray(): Converts the ArrayList to a regular array of objects.
   • toArray(T[] a): Converts the ArrayList to an array of the specified type T.

8. Iterating Over ArrayList:

   • You can use the enhanced for loop (for-each loop) or the traditional for loop to iterate over the elements in an ArrayList.

javaCopy code
import java.util.ArrayList;

public class ArrayListMethodsExample {
    public static void main(String[] args) {
        ArrayList<Integer> numbers = new ArrayList<>();

        // Adding elements
        numbers.add(10);
        numbers.add(20);
        numbers.add(30);

        // Accessing elements
        int secondNumber = numbers.get(1); // 20

        // Removing elements
        numbers.remove(0); // Remove 10

        // Size and checking empty
        int size = numbers.size(); // 2
        boolean isEmpty = numbers.isEmpty(); // false

        // Searching elements
        boolean contains30 = numbers.contains(30); // true
        int index = numbers.indexOf(30); // 1

        // Sublist operations
        ArrayList<Integer> sublist = numbers.subList(0, 1); // [20]

        // Converting to array
        Integer[] numbersArray = numbers.toArray(new Integer[0]);
    }
}

These are just some of the many methods available in the ArrayList class. The Java ArrayList provides a rich set of operations to manage and manipulate collections of elements efficiently. For more details and additional methods, you can refer to the official Java documentation for the ArrayList class.

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