title: Java isNan how it works?
body: <p>I was looking at the <code>openjdk-1.7.0_25</code> source code and I have seen this method:</p>
  
  <pre><code>/**
   * Returns {@code true} if the specified number is a
   * Not-a-Number (NaN) value, {@code false} otherwise.
   *
   * @param   v   the value to be tested.
   * @return  {@code true} if the argument is NaN;
   *          {@code false} otherwise.
   */
  static public boolean isNaN(float v) {
      return (v != v);
  }
  </code></pre>
  
  <p>I can't understand how it works, when this method can return <code>true</code>?</p>