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Java Local Development Environments Advanced Tooling Finishing TreeStory

natalie murphy
natalie murphy
2,595 Points

It's hard to debug without seeing the test that is failing.

line 79 there is a null pointer exception. I added || choice == null but that did not seem to fix the problem.

package com.teamtreehouse;

public class Main {

   public static void main(String[] args) {
      Prompter prompter = new Prompter();
      String story = "Thanks __name__ for helping me out.  You are really a __adjective__ __noun__ and I owe you a __noun__.";
      Template tmpl = new Template(story);
package com.teamtreehouse;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class Prompter {
   private BufferedReader mReader;
   private Set<String> mCensoredWords;

   public Prompter() {
      mReader = new BufferedReader(new InputStreamReader(System.in));

   private void loadCensoredWords() {
      mCensoredWords = new HashSet<String>();
      Path file = Paths.get("resources", "censored_words.txt");
      List<String> words = null;
      try {
         words = Files.readAllLines(file);
      } catch (IOException e) {
         System.out.println("Couldn't load censored words");

   public void run(Template tmpl) {
      List<String> results = null;
      try {
         results = promptForWords(tmpl);
         System.out.printf("Your TreeStory:%n%n%s", tmpl.render(results));
      } catch (IOException e) {
         System.out.println("There was a problem prompting for words");

    * Prompts user for each of the blanks
    * @param tmpl The compiled template
    * @return
    * @throws IOException
   public List<String> promptForWords(Template tmpl) throws IOException {
      List<String> words = new ArrayList<>();
      for (String phrase : tmpl.getPlaceHolders()) {
         String word = promptForWord(phrase);
      return words;

    * Prompts the user for the answer to the fill in the blank.  Value is guaranteed to be not in the censored words list.
    * @param phrase The word that the user should be prompted.  eg: adjective, proper noun, name
    * @return What the user responded
   public String promptForWord(String phrase) throws IOException {
      System.out.printf("Can you give me a %s? %n", phrase);
      String choice = mReader.readLine();
      if (mCensoredWords.contains(choice)) {
         System.out.printf("That's a censored word, try again.%n");
         choice = promptForWord(phrase);
      else if (choice.isEmpty()) {
         System.out.printf("try again.%n");
         choice = promptForWord(phrase);
      return choice;
#  This is essentially what I am testing 
1.  The user is prompted for a new string template (the one with the double underscores in it).

  a. The prompter class has a new method that prompts for the story template, and that method is called.

2.  The user is then prompted for each word that has been double underscored.

   a. The answer is checked to see if it is contained in the censored words.
      User is continually prompted until they enter a valid word

3.  The user is presented with the completed story

1 Answer

Have you tried checking if choice is null before trying to use it in if (mCensoredWords.contains(choice)) {?

If you use choice.isEmpty() || choice == null, Java will try to find the result of the left side before trying to find the result of the right side. If choice is in fact null, then the left side gives you a null pointer exception and the right side is not computed. If instead you use choice == null || choice.isEmpty() when the value of choice is null, Java will determine that choice == null is true and ignore the right side.