title: Why StringBuilder throws NullPointerException
body: <p>This question may be redundant but I really don't understand why the following code throws: <code>Exception in thread "main" java.lang.NullPointerException</code></p>
  
  <pre><code>public class NewClass {
      static StringBuilder SB;
      public static void main(String[] args) {
          SB.append("Tesing");
          System.out.println(SB);
      }
  
  }
  </code></pre>