How to compare each element in my arraylist to find the nth smallest of the two arrays?

import java.util.*;

public class Main {

	public static void main(String[] args) {
		// this section of code will require user input to have the value of n to be set
		System.out.println(("What number would you like to set n equal to ?"));
		Scanner sc = new Scanner(System.in);
		System.out.print(("n= "));
		int value = sc.nextInt();
		System.out.println((""));

		// this section of code set the two array only to hold the value of n
		Random rand = new Random();
		ArrayList<Integer> setA = new ArrayList<Integer>();
		for (int i = 0; i < value; i++) {
			int picks = rand.nextInt(1000);
			setA.add(picks);
		}
		Collections.sort(setA);
		System.out.println(setA);


		ArrayList<Integer> setX = new ArrayList<Integer>();
		for (int k = 0; k < value; k++) {
			int picks = rand.nextInt(1000);
			setX.add(picks);
		}
		Collections.sort(setX);
		System.out.println(setX);
		solution(setA,setX,value);
	}

	private static int solution(ArrayList<Integer> A1, ArrayList<Integer> X1, int value) {
		// This section of code is where the arrays will be compared to find the nth smallest.
		ArrayList<Integer> setF = new ArrayList<Integer>();
		for (int c = 0; c < A1.size(); c++) {
			for(int k = 0; k < X1.size(); k++) {
				if(A1.get(c) < X1.get(k)) {

				}
			}
		}

		System.out.print(setF);
		return value;
	}
}

So far i have my program set up to have the user enter a number that will be used for the size of the array. Once the number has been entered the arrays are created with random numbers that will be place in order. Next I would like to go through each element of my arrays and compare to see which numbers can be placed in my Final array. In my final array is the nth smallest number which will be return. I can not merge the two array together.

For example if n = 10 below are my two arrays

> A [124, 264, 349, 450, 487, 641, 676, 792, 845, 935]

> B [2, 159, 241, 323, 372, 379, 383, 475, 646, 836]

124 < 2 this statement is false so 2 would get added to my final array list. Array B should move to the next element in the list.
124 < 159 this is true so 124 gets added to my final array list. Array A should move to the next element in the list.
264 < 159 this statement is false so 159.

Final Array [2,124, 159,...]

n smallest is 383.

Hopefully that example gives you an ideal of what I'm trying to accomplish.if you have something better let me know please..

Your solution would work but you can make your solution's time complexity o(n) rather than o(n^2).

What you could do is, since the arrays are equally sorted, you can compare both elements at position zero (like you're doing) and then whichever element is smaller, pop that element from the array and add it to the final array. Keep testing the zero(th) indexed element until one of the arrays is empty. Once its empty, you can just append the remaining other array on the end of the final array and that should achieve what you want.

So in some java code implementation:

private ArrayList<Integer> sortTwoArrays(ArrayList<Integer> arrayA, ArrayList<Integer> arrayB) {
    ArrayList<Integer> finalArray = new ArrayList<>();
    while(!arrayA.isEmpty() && !arrayB.isEmpty()) {
        if (arrayA.get(0) < arrayB.get(0)) {
            // remove element and store
            finalArray.add(arrayA.remove(0));
        }
        else {
            finalArray.add(arrayB.remove(0));
        }
    }

    // Find out which array is not empty
    // Adds remaining contents of non-empty array to end of finalArray
    if (!arrayA.isEmpty()) {
        finalArray.addAll(arrayA);
    }
    else if (!arrayB.isEmpty()) {
        finalArray.addAll(arrayB);
    }

    return finalArray;
}

To get the nth smallest value, just add the value the user passes in as an argument to the function and then when you're returning the function, just return finalArray.get(nthIndex)

Example code showcase here.

> Note: The original two ArrayLists will get destroyed from this method
>
> If you want preserve the two arrays, I recommend keeping track of both indexes in the list inside variables and then incrementing based on when one item is less than another. Additionally, change the If statement check after the whie-loop from an isEmpty() check to a comparison like so indexOfArrayA == arrayA.size() - 1.

I hope this helps in anyway.