Need help fillng in the code with JAVA

import java.util.Map; import java.util.Scanner; import java.util.TreeMap; import java.io.File; import java.io.FileNotFoundException; /** This program is an example from Big Java, Chapter 16. It prints the frequencies of all words in a given file. The basic idea is to make a map from word to frequency. For each word in the file, put it in the map with a frequency of one if it wasn't there already, otherwise increment its frequency. */ public class WordFrequency { public static void main(String[] args) throws FileNotFoundException {  //-----------Start below here. To do: approximate lines of code = 6 // 1. let frequencies be a map from String to Integer (a TreeMap) //2. let scanner be based on file "catInHat.txt" while (scanner.hasNext()) { // String word = clean(scanner.next());// //3. Integer count = frequency of this word //4. update count when it is null //5. update count when it is not null //6. update the map }//closing the while  //-----------------End here. Please do not remove this comment. Reminder: no changes outside the todo regions. // Print all words and counts for (String key : frequencies.keySet()) { System.out.printf("%-20s%10d ", key, frequencies.get(key)); } } /** Removes characters from a string that are not letters. @param str a string @return a string with all the letters from str */ public static String clean(String str) { String result = ""; for (int i = 0; i < str.length(); i++) { char c = str.charAt(i); if (Character.isLetter(c)) { result = result + c; } } return result.toLowerCase(); } }