ArrayList Coding Activity

Objective:

Students will create, manipulate, and sort an ArrayList of integers.

Activity Outline:

  1. Create an ArrayList:
    • Task: Create an ArrayList of integers and add 5 elements of your choice.
    • Hint: Use the ArrayList class and the .add() method to add elements.
  2. Modify an Element:
    • Task: Change the second element (index 1) of the ArrayList to a new value (e.g., 100).
    • Hint: The .set() method allows you to update an element at a specific index.
  3. Remove an Element:
    • Task: Remove the third element (index 2) from the ArrayList.
    • Hint: Use the .remove() method to delete an element by its index.
  4. Search for an Element:
    • Task: Check if a specific number (e.g., 30) is in the ArrayList and print a message based on whether it is found or not.
    • Hint: The .contains() method can be used to check for the presence of an element.
  5. Loop Through the ArrayList:
    • Task: Use a for loop to print each element of the ArrayList.
    • Hint: You can use a traditional for loop or an enhanced for loop (for-each) to iterate through the elements.
  6. Sort the ArrayList:
    • Task: Sort the ArrayList in ascending order.
    • Hint: Use Collections.sort() to sort the ArrayList.
  7. Print the Sorted ArrayList:
    • Task: Print the sorted ArrayList to see the updated order of the elements.
    • Hint: Use System.out.println() to print the sorted list.
import java.util.ArrayList;
import java.util.Collections;

public class HackYum {
    public static void main(String[] args) {
        ArrayList<Integer> numbers = new ArrayList<>();
        numbers.add(20);
        numbers.add(10);
        numbers.add(40);
        numbers.add(30);
        numbers.add(50);
        
        System.out.println("Original ArrayList: " + numbers);

        numbers.set(1, 45678);
        System.out.println("After modifying second element: " + numbers);

        numbers.remove(2);
        System.out.println("After removing the third element: " + numbers);

        int searchValue = 30;
        if (numbers.contains(searchValue)) {
            System.out.println(searchValue + " is in the ArrayList.");
        } else {
            System.out.println(searchValue + " is not in the ArrayList.");
        }

        System.out.println("Looping through the ArrayList:");
        for (int number : numbers) {
            System.out.println(number);
        }

        Collections.sort(numbers);
        System.out.println("Sorted ArrayList: " + numbers);
    }
}

HackYum.main(null);

Original ArrayList: [20, 10, 40, 30, 50]
After modifying second element: [20, 45678, 40, 30, 50]
After removing the third element: [20, 45678, 30, 50]
30 is in the ArrayList.
Looping through the ArrayList:
20
45678
30
50
Sorted ArrayList: [20, 30, 50, 45678]