Example: Reverse Array Using Collections.reverse() in Java

// Reverse Array Using Collections.reverse()
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        // Step 1: Declare and initialize the original array (primitive type)
        int[] originalIntArray = {11, 22, 33, 44};
        System.out.println("Original int[]: " + Arrays.toString(originalIntArray));

        // Step 2: Convert primitive int[] to List<Integer>
        List<Integer> list = new ArrayList<>();
        for (int i : originalIntArray) {
            list.add(i);
        }
        System.out.println("Converted List: " + list);

        // Step 3: Use Collections.reverse() to reverse the list
        Collections.reverse(list);

        // Step 4: Print the reversed list
        System.out.println("Reversed List: " + list);

        // Step 5: (Optional) Convert the reversed list back to an int[] if needed
        int[] reversedIntArray = new int[list.size()];
        for (int i = 0; i < list.size(); i++) {
            reversedIntArray[i] = list.get(i);
        }
        System.out.println("Reversed int[] (from list): " + Arrays.toString(reversedIntArray));

        // --- Example with an Integer array directly (no primitive conversion needed initially) ---
        Integer[] integerArray = {100, 200, 300};
        System.out.println("\nOriginal Integer[]: " + Arrays.toString(integerArray));
        List<Integer> integerList = Arrays.asList(integerArray); // Convert Integer[] to List directly
        
        // Note: Arrays.asList returns a fixed-size list. If you need to modify its structure (add/remove),
        // wrap it in a new ArrayList: List<Integer> modifiableList = new ArrayList<>(Arrays.asList(integerArray));

        Collections.reverse(integerList);
        System.out.println("Reversed Integer List: " + integerList);
        System.out.println("Original (now reversed) Integer[]: " + Arrays.toString(integerArray)); // original array is also reversed
    }
}