Thread: i get an error when i run it

import java.io.File;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Scanner;
 
 
 
public class WordCounter 
{
	// 2 fields for file name and hashmap
	private ArrayList<String> fn;
	private HashMap <String, Integer> hm;
	//private Scanner x;
 
	// constructor
	public WordCounter(String frame)
	{
		countwords(frame);
 
	}
	public ArrayList<String> getfn() {
		return fn;
	}
	public HashMap<String, Integer> gethm() {
		return hm;
	}
	// methods
	private void countwords (String fname)
	{
		try{
			Scanner x = new Scanner (new File(fname));
			while (x.hasNextLine()){
				String[]words = x.nextLine().split("[^a]+");
				for(String s: words)
					System.out.println(s);
		System.out.println(Collections.frequency(fn, hm));
		}}
		catch (Exception e){
			System.err.println(e);
		}
	}
	public void print() {
		System.out.println("Word:\t\tFrequency:");
		System.out.println("====================================");
		for(int i=0; i< fn.size(); i++){
			System.out.println();
		}
	}
 
 
	public static void main(String[] args) throws Exception  
	{
		String fname = "test-file.txt";
		if (args.length > 0)
			fname = args[0];
 
		WordCounter wc = new WordCounter(fname);
		wc.print();
	}
 
 
}

Output

Word: Frequency:
====================================
java.lang.NullPointerException
Exception in thread "main" java.lang.NullPointerException
at WordCounter.print(WordCounter.java:46)
at WordCounter.main(WordCounter.java:59)

so the line is :

for(int i=0; i< fn.size(); i++){

however i beilieve i need that for the program.

okey i figure out why is null, because fn doesnt have a value set. so i need to read the ttext file that i imported in to my project (just reads 1 letter like ...... A ) and prints how many times its prints out.