Calculate Postfix Expressions using Queues in Java

Problem:

You are given a list of postfix expressions. Calculate the result of the expressions using a stack. The first line of input n is the number of test cases followed by n expressions. Each expression begins with an integer t representing the number of characters in the expression, and then t characters follow which are either a number or an operand.

Output:

3
3 2 3 *
5 5 4 2 + -
9 5 6 2 + * 12 4 / -

6
1
37

Solution:

import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
public class ProblemC {

 public static void main(String[] args) {
  
  Queue<Integer> q = new LinkedList<Integer>();
  String output = "";
  Scanner scan = new Scanner(System.in);
  
  int testCases = scan.nextInt();
  
  for (int cases = 0; cases < testCases; cases++) {
   
   int t = scan.nextInt();
   
   for (int i = 0; i < t; i++)
    q.offer(scan.nextInt());
   
   output +=( "Test case "+(cases+1)+":" + "\n");
   
   while (!q.isEmpty()) {
    if (q.peek()%2 == 0)
     output += (q.poll() + "\n");
    else {
     output+= q.poll()+" ";
     output += q.poll() + "\n";
    }
   }
  }
  
  System.out.println(output);
 }
}