 <p>To test if the <code>JComboxBox</code> reference is <code>null</code>, you can compare it with <code>null</code> using the <code>==</code> operator. To test if the combo-box contains any items, you can use the instance method <a href="http://download.oracle.com/javase/1.4.2/docs/api/javax/swing/JComboBox.html#getItemCount%28%29" rel="nofollow"><code>getItemCount</code></a>, which returns the number of items it contains. </p> <pre><code>JComboxBox box = ... boolean boxIsNull = (box == null); // answers the title of the question boolean boxHasItems = (box.getItemCount() &gt; 0); </code></pre>