Map<Object, Object> result = Maps.newHashMap();
            for (Object key : keys) {
              Object value = new Object();
              result.put(key, value);
              // add extra entries
              result.put(value, key);
            }
            return result;
          }
        };
    LoadingCache<Object, Object> cache = CacheBuilder.newBuilder().build(loader);

            Map<Object, Object> result = Maps.newHashMap();
            for (Object key : keys) {
              Object value = new Object();
              result.put(key, value);
              // add extra entries
              result.put(value, key);
            }
            return result;
          }
        };
    LoadingCache<Object, Object> cache = CacheBuilder.newBuilder().build(loader);