src/main/java/com/seanchenxi/gwt/storage/client/StorageExt.java
public <T> boolean containsKey(StorageKey<T> key) {
    return storage.getItem(key.name()) != null;
  }
public <T> boolean containsKey(StorageKey<T> key) {
    return storage.getItem(key.name()) != null;
  }
Test if this storage contains a value for the specified key.

<p>
{@link StorageKeyFactory} is preferred to get a {@link StorageKey} instance for primitive types.
</p>

@param key the key whose presence in this storage is to be tested
@param <T> the type of stored value
@return <tt>true</tt> if this storage contains a value for the specified key.