title: Gson fromJson() returns object with null attrubutes
body: <p>I'm trying to create some Java objects using this line:</p>
  
  <p><code>Quiz currentQuiz = gson.fromJson(json, Quiz.class);</code></p>
  
  <p>But the all I get is this:</p>
  
  <p><img src="https://i.stack.imgur.com/I3Fxj.png" alt="Quiz object after fromJson"></p>
  
  <p>Here are my object classes:</p>
  
  <p>Quiz:</p>
  
  <pre><code>public class Quiz {
  
  private String ref;
  private String broadcast_dt;
  private Question[] questions;
  
  public Quiz() {
      // TODO Auto-generated constructor stub
  }
  
  public String getRef() {
      return ref;
  }
  
  public void setRef(String ref) {
      this.ref = ref;
  }
  
  public String getBroadcast_dt() {
      return broadcast_dt;
  }
  
  public void setBroadcast_dt(String broadcast_dt) {
      this.broadcast_dt = broadcast_dt;
  }
  
  public Quiz(String ref, String broadcast_dt, Question[] questions) {
      super();
      this.ref = ref;
      this.broadcast_dt = broadcast_dt;
      this.questions = questions;
  }
  
  public Question[] getQuestions() {
      return questions;
  }
  
  public void setQuestions(Question[] questions) {
      this.questions = questions;
  } 
  }
  </code></pre>
  
  <p>Question:</p>
  
  <pre><code>public class Question {
  
  private int question_number;
  private String question_text;
  private Answer[] answers;
  
  public Question(){
  
  }
  
  public Question(int question_number, String question_text, Answer[] answers) {
      super();
      this.question_number = question_number;
      this.question_text = question_text;
      this.answers = answers;
  }
  
  public int getQuestion_number() {
      return question_number;
  }
  
  public void setQuestion_number(int question_number) {
      this.question_number = question_number;
  }
  
  public String getQuestion_text() {
      return question_text;
  }
  
  public void setQuestion_text(String question_text) {
      this.question_text = question_text;
  }
  
  public Answer[] getAnswers() {
      return answers;
  }
  
  public void setAnswers(Answer[] answers) {
      this.answers = answers;
  }
  }
  </code></pre>
  
  <p>Answer:</p>
  
  <pre><code>public class Answer {
  
  private String answer_text;
  private boolean correct_yn;
  
  public Answer(){
  
  }
  
  public String getAnswer_text() {
      return answer_text;
  }
  
  public void setAnswer_text(String answer_text) {
      this.answer_text = answer_text;
  }
  
  public boolean isCorrect_yn() {
      return correct_yn;
  }
  
  public void setCorrect_yn(boolean corrent_yn) {
      this.correct_yn = corrent_yn;
  }
  }
  </code></pre>
  
  <p>And here is my JSON:</p>
  
  <pre><code>{
  "quiz": {
      "ref": "45g36745bu46",
      "broadcast_dt": "2013-03-03T00:00:00Z",
      "questions": [
          {
              "question_number": 1,
              "question_text": "Example question one",
              "answers": [
                  {
                      "answer_text": "Answer one",
                      "correct_yn": false
                  },
                  {
                      "answer_text": "Answer two",
                      "correct_yn": true
                  },
                  {
                      "answer_text": "Answer three",
                      "correct_yn": false
                  }
              ]
          },
          {
              "question_number": 2,
              "question_text": "Question number two",
              "answers": [
                  {
                      "answer_text": "Something",
                      "correct_yn": false
                  },
                  {
                      "answer_text": "Something else",
                      "correct_yn": false
                  },
                  {
                      "answer_text": "Another thing",
                      "correct_yn": true
                  }
              ]
          },
          {
              "question_number": 3,
              "question_text": "And a third question with some additional question text appearing here.",
              "answers": [
                  {
                      "answer_text": "Cow",
                      "correct_yn": false
                  },
                  {
                      "answer_text": "Pig",
                      "correct_yn": true
                  }
              ]
          }
      ]
  }
  }
  </code></pre>
  
  <p>Any ideas why this happens? I don't get an error message or LogCat output.</p>