WordCount.java

import java.util.HashMap;

/**
 * This class has a word list that is used to store the words. It provides some functionality such as to add
 * a word to the list, count a number of time a word that is in the list, and remove all
 * words in the list.
 */
public class WordCount {

    //HashMap collection to store words
    private HashMap<String, Integer> wordList;

    /**
     * This constructor initializes the wordList 
     */
    public WordCount() {
        wordList = new HashMap<String, Integer>(); 
    }

    /**
     * This constructor initializes the word list to the words in the string,
     * separated by spaces.if String words is null or empty, initialize wordList
     * to be empty HashMap.
     * @param a String of words
     */
    public WordCount(String words) {
        if(words == null || words.isEmpty() ){
            wordList = new HashMap<String, Integer>(); 
        } else {
        
        String[] spacer = words.split(" "); 
        wordList = new HashMap<>(); 
        
            for (String token: spacer){ 
                if(wordList.containsKey(token)){ 
                    int count = wordList.get(token); 
                    wordList.replace(token, ++count); 
                } else{ 
                    wordList.put(token, 1); 
                } 
            } 
        }
        
    }

    /**
     * This method adds a word to the list of words stored by the object. If
     * String toAdd is null or empty, do not add to the word list. 
     * @param toAdd
     */
    public void addWord(String toAdd) {
        
        if(!(toAdd==null)){ // If the word is already present in the hashmap then increase its count 
            if(wordList.containsKey(toAdd)){ 
                int count = wordList.get(toAdd); 
                wordList.replace(toAdd, ++count); 
            } else {
                wordList.put(toAdd, 1); 
            } 
        } 
    }

    /**
     * This method removes all words from the list of words stored by the object
     */
    public void startOver() {
        wordList.clear();
    }

    /**
     * This method returns an integer representing the number of times that a word is
     * in the list of words stored by the object. If the String word is null or
     * empty return 0
     * @param the word to be checked for number of time that in the list of words
     * @return the number of times a word is in the list
     */
    public int countWord(String word) {
        if(wordList.containsKey(word)){ 
            return wordList.get(word); 
        } else { 
            return 0; 
        } 
    }

}