what is the time complexity of this program? is it theta(nlogn)?

code:

// Java program to merge to unsorted stacks

// into a third stack in sorted way.

import java.io.*;

import java.util.*;

public class GFG {

// This is the temporary stack

static Stack res = new Stack();

static Stack tmpStack = new Stack();

// Sorts input stack and returns

// sorted stack.

static void sortStack(Stack input)

{

while (input.size() != 0)

{

// pop out the first element

int tmp = input.peek();

input.pop();

// while temporary stack is not empty and

// top of stack is greater than temp

while (tmpStack.size() != 0 &&

tmpStack.peek() > tmp)

{

// pop from temporary stack and push

// it to the input stack

input.push(tmpStack.peek());

tmpStack.pop();

}

// push temp in tempory of stack

tmpStack.push(tmp);

}

}

static void sortedMerge(Stack s1,

Stack s2)

{

// Push contents of both stacks in result

while (s1.size() != 0) {

res.push(s1.peek());

s1.pop();

}

while (s2.size() != 0) {

res.push(s2.peek());

s2.pop();

}

// Sort the result stack.

sortStack(res);

}

// main function

public static void main(String args[])

{

Stack s1 = new Stack();

Stack s2 = new Stack();

s1.push(34);

s1.push(3);

s1.push(31);

s2.push(1);

s2.push(12);

s2.push(23);

sortedMerge(s1, s2);

System.out.println("Sorted and merged stack :");

while (tmpStack.size() != 0) {

System.out.print(tmpStack.peek() + " ");

tmpStack.pop();

}

}

}