title: Java NullPointerException
body: <p>I get a <code>java.lang.NullPointerException</code> in my Class Article in <code>line 5</code>.</p>
  
  <p>In one class I create the object <code>Article article = new Article()</code>,
  then I call <code>article.addPrice(quantity, price);</code> with <code>quantity</code> being an Integer with the value '<code>1</code>' and <code>price</code> being a Float with the value '<code>1.32</code>'.</p>
  
  <pre><code>1: public class Article {
  2:  private List prices;
  3:  public void addPrice(Integer quantity, Float qtyPrice){
  4:      Price price = new Price(quantity, qtyPrice);
  5:      this.prices.add(price);
  6:  }
  7: }
  </code></pre>