TopN.java

package test;

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

public class TopN {
	
	public static void GetNum(String fileName, int N) {
		
		PriorityQueue<Integer> priorityQueue = new PriorityQueue<Integer>(N);
		BufferedReader bufferedReader = null;
	  
		try {
	    
			bufferedReader = new BufferedReader(new FileReader(fileName));
			String line = bufferedReader.readLine();

			while (line != null) {
				try {
					int number = Integer.valueOf(line);
					if (priorityQueue.size() < N) {
						priorityQueue.add(number);
					} else {
						int head = priorityQueue.element();												
						if (number > head) {
							priorityQueue.add(number);
							priorityQueue.remove();
						}
					}
				} catch (NumberFormatException e) {
					System.out.println("Error");
				}
				line = bufferedReader.readLine();
			}
			System.out.println(priorityQueue.toString());
		} catch(Exception ex) {
	    	System.out.println("Error");
		}
	}
}