code>synchronized (cache) {
     if (cache.get(key) == null) {
         cache.put(key, value);
     </code>
   }}</pre>

 <p>This class does not allow null to be used as a key or value. A return
 value of null from <code><a href="../../../reference/android/util/LruCache.html#get(K)">get(K)</a></code>, <code><a href="../../../reference/android/util/LruCache.html#put(K, V)">put(K, V)</a></code> or <code><a href="../../../reference/android/util/LruCache.html#remove(K)">remove(K)</a></code> is
 unambiguous: the