Question

I need help running this code.

import java.util.*;
import java.io.*;

public class wordcount2 {
    public static void main(String[] args) {
        if (args.length !=1) {
            System.out.println(
                               "Usage: java wordcount2 fullfilename");
            System.exit(1);
        }
       
        String filename = args[0];
     
        // Create a tree map to hold words as key and count as value
        Map<String, Integer> treeMap = new TreeMap<String, Integer>();
       
        try {
            @SuppressWarnings("resource")
            Scanner input = new Scanner(new File(filename));
           
            
            
            while (input.hasNext()) {
                String line = input.nextLine();
                String[] words = line.split(" A [ @!~{}\\[\\]$#^&*\n\t\r.,;?'\")(]");
                // question: why do we need this?
               
                for (int i = 0; i < words.length; i++) {
                    if (words[i].trim().length() > 0 && words[i].trim().matches("[A-Z|a-z]+")) {
                        String key = words[i].toLowerCase();
                        // question: what is trim used for here?
                        if (treeMap.get(key) != null) {
                            int count = treeMap.get(key);
                            count++;
                            treeMap.put(key, count);
                        }
                        else {
                            treeMap.put(key, 1);
                        }
                        // question: can you simplify the code here?
                    }
                }
            }
        }
        catch (Exception ex) {
            ex.printStackTrace();
        }
       
        // Get an entry set for the tree map
        Set<Map.Entry<String, Integer>> entrySet = treeMap.entrySet();
       
        // Display words in alphabetical order
        System.out.println("\nDisplay words and their count in " +
                           " ascending order of the words");
        for (Map.Entry<String, Integer> entry: entrySet)
            System.out.println(entry.getValue() + "\t" + entry.getKey());
    }
}