Write a program, topN, that given an arbitrarily large file and a number, N, containing individual numbers on each line (e.g. 200Gb file), will output the largest N numbers, highest first. Tell me about the run time/space complexity of it, and whether you think there's room for improvement in your approach.

input_file

10
1
8
-20
4
2
79
123123
8
9
22
24
3

TopNumbers.java

package com.yekmer.interview.intercom;

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.PriorityQueue;
import java.util.Stack;

public class TopNumbers {
	
	public static void main(String[] args) {
		int N = 5;
		topN("input_file", N);
	}
	
	//Assume file is one integer by one row
	public static void topN(String fileName, int N) {
		PriorityQueue<Integer> priorityQueue = new PriorityQueue<Integer>(N);
        Stack<Integer> resultStack = new Stack<Integer>();
        BufferedReader bufferedReader = null;
	    try {
	    	bufferedReader = new BufferedReader(new FileReader(fileName));
	    	//reading line by line will not fill memory
	        String line = bufferedReader.readLine();

	        while (line != null) {
	        	try {
	        		int mInt = Integer.valueOf(line);
	        		priorityQueue.add(mInt);
	    			if(priorityQueue.size() > N) {
	    				priorityQueue.remove();
	    			}
				} catch (NumberFormatException e) {
					System.out.println("Continues if there is a non int row");
				}
	            line = bufferedReader.readLine();
	        }
			for(int i = 0; i < N; i++) {
				resultStack.add(priorityQueue.remove());
			}
	    //we can handle different type of exceptions here, it will be faster to execute
	    } catch(Exception ex) {
	    	System.out.println("There is an error, program exits");
	    } finally {
    		try {
    			bufferedReader.close();	
			} catch (Exception e) {
				System.out.println("Error while closing reader");
			}
	    }
	    for(int i = 0; i < N; i++) {
			System.out.println(resultStack.pop());
		}
	}

}