Write a Java program to find the second largest element in an array.

This program finds the second largest element in an array.

class Main {
    public static void main(String[] args) {
        int[] arr = {3, 56, 8, 43, 44};  // Example array

        // Call the method to find the second largest element
        int secondLargest = findSecondLargest(arr);
        
        // Print the second largest element if found
        if (secondLargest != -1) {
            System.out.println("Second largest element: " + secondLargest);
        } else {
            System.out.println("There are no second largest element.");
        }
    }

    // Method to find and return the second largest element in the array
    public static int findSecondLargest(int[] arr) {
        int largest = Integer.MIN_VALUE;
        int secondLargest = Integer.MIN_VALUE;

        // Loop through the array to find the largest and second largest elements
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] > largest) {
                secondLargest = largest;  // Update second largest
                largest = arr[i];  // Update largest
            } else if (arr[i] > secondLargest && arr[i] != largest) {
                secondLargest = arr[i];  // Update second largest
            }
        }

        // If second largest is still Integer.MIN_VALUE, return -1 indicating no second largest element
        if (secondLargest == Integer.MIN_VALUE) {
            return -1;  // No second largest element found
        } else {
            return secondLargest;  // Return the second largest element
        }
    }
}

Output:

Second largest element: 44

How It Works

1. Initialization:
   • largest and secondLargest are initialized to Integer.MIN_VALUE to ensure they can store any value in the array.
2. Finding the Largest and Second Largest:
   • If the current element (arr[i]) is greater than largest:
     • Update secondLargest to the value of largest.
     • Update largest to the current element.
   • Else if the current element is greater than secondLargest and not equal to largest, update secondLargest.
3. Edge Case Handling:
   • If secondLargest remains Integer.MIN_VALUE, the method returns -1, indicating there is no valid second largest element.
4. Output:
   • If a second largest element exists, it prints the value. Otherwise, it prints a message saying no second largest element exists.

Edge Cases

1. Array with One Element:
   • Input: arr = {5}
   • Output: There are no second largest element.
2. Array with Identical Elements:
   • Input: arr = {3, 3, 3, 3}
   • Output: There are no second largest element.
3. Negative Numbers:
   • Input: arr = {-3, -1, -7, -5}
   • Output: Second largest element: -3

Advantages

• Efficient: Time complexity is O(n) with a single loop through the array.
• Space Efficient: No additional data structures are used, so space complexity is O(1).