ArrayList Manipulation: add, remove Elements, find size

Problem Statement: Write a Java program to create an ArrayList of integers, add elements, remove elements, and find the size of the list.

Here’s a Java program that demonstrates how to create an ArrayList of integers, add elements to it, remove elements from it, and find the size of the list. I’ll provide a thorough explanation of the logic behind each step.

package com.javacodepoint.collection;

import java.util.ArrayList;

public class ArrayListManipulation {
	
	public static void main(String[] args) {
		// Create an ArrayList to store integers
		ArrayList<Integer> numbers = new ArrayList<>();

		// Adding elements to the ArrayList
		numbers.add(10); // Add the integer 10 to the list
		numbers.add(20); // Add the integer 20 to the list
		numbers.add(30); // Add the integer 30 to the list

		System.out.println("ArrayList after adding elements: " + numbers);

		// Removing an element from the ArrayList
		numbers.remove(1); // Remove the element at index 1 (20)

		System.out.println("ArrayList after removing element at index 1: " + numbers);

		// Finding the size of the ArrayList
		int size = numbers.size(); // Get the number of elements in the list

		System.out.println("Size of the ArrayList: " + size);
	}
}

OUTPUT:

ArrayList after adding elements: [10, 20, 30]
ArrayList after removing element at index 1: [10, 30]
Size of the ArrayList: 2

Explanation:

1. Import Statement: The import statement is used to import the necessary classes. In this case, we’re importing the ArrayList class from the java.util package.
2. Creating an ArrayList: We create an ArrayList named numbers that will store integers. We specify the type of elements the list will hold using the angle brackets (<>) and the type parameter (Integer in this case).
3. Adding Elements: We use the add() method to add integers to the numbers list. We add three integers: 10, 20, and 30. The add() method appends elements to the end of the list.
4. Printing the ArrayList: We use the System.out.println() statement to print the contents of the numbers list after adding the elements.
5. Removing an Element: We use the remove() method to remove an element from the list. In this case, we remove the element at index 1, which is the integer 20.
6. Printing the Modified ArrayList: We print the contents of the numbers list again after removing the element at index 1.
7. Finding the Size: We use the size() method to find the number of elements in the numbers list. The result is stored in the size variable.
8. Printing the Size: We print the size of the numbers list using the System.out.println() statement.

By following these steps, the program demonstrates how to create an ArrayList of integers, add elements to it, remove elements from it, and find the size of the list. This is a fundamental example of working with collections in Java.

See also: List Manipulation: Reverse a List.