Week 3: Objects, files and exceptions/5b. Second smallest without side effects

Write the method

int secondSmallest(ArrayList<Integer> numbers)

...which returns the second smallest element in the list. 
The method must not change the order of the elements in the list.

Example method call:
public static void main(String[] parameters){
    ArrayList<Integer> numbers = new ArrayList<>();
    numbers.add(5);
    numbers.add(1);
    numbers.add(8);
    numbers.add(3);
    numbers.add(7);

    System.out.println("List before: " + numbers);
    System.out.println("Second smallest: " + secondSmallest(numbers));
    System.out.println("List after: " + numbers);   
}

Program outputs:
List before: [5, 1, 8, 3, 7]
Second smallest: 3
List after: [5, 1, 8, 3, 7]








import java.util.Random;
import java.util.ArrayList;
import java.util.Collections;

public class Test{
    public static void main(String[] args){
        final Random r = new Random();
        
        
        int[][] s = {{3,2,1,4}, {10,20,40,50,30,60}, {9,7,5,3,8,6,4,2}, {25,5,20,15,10}};
        
        for (int[] pa : s) {
            ArrayList<Integer> lista = new ArrayList<>();
            for (int l : pa) lista.add(l);
            
            System.out.println("List before: ");
            System.out.println("" + lista);
            System.out.println("Second smallest: " + secondSmallest(lista));
            System.out.println("List after: ");
            System.out.println(lista);
            System.out.println("");
            
        }
    }
    

    //ADD
    public static int secondSmallest(ArrayList<Integer> numbers){
        int smallest = Collections.min(numbers);
        int secondSmallest = Collections.max(numbers);
        for (int i : numbers) {
            if (i > smallest && i < secondSmallest) {
                secondSmallest = i;
            }
        }
        return secondSmallest;
    }





}





List before: 
[3, 2, 1, 4]
Second smallest: 2
List after: 
[3, 2, 1, 4]

List before: 
[10, 20, 40, 50, 30, 60]
Second smallest: 20
List after: 
[10, 20, 40, 50, 30, 60]

List before: 
[9, 7, 5, 3, 8, 6, 4, 2]
Second smallest: 3
List after: 
[9, 7, 5, 3, 8, 6, 4, 2]

List before: 
[25, 5, 20, 15, 10]
Second smallest: 10
List after: 
[25, 5, 20, 15, 10]