code: public static <K, V> V createIfAbsentUnchecked(final ConcurrentMap<K, V> map,
              final K key, final ConcurrentInitializer<V> init) {
          try {
              return createIfAbsent(map, key, init);
          } catch (final ConcurrentException cex) {
              throw new ConcurrentRuntimeException(cex.getCause());
          }
      }
docs: Checks if a concurrent map contains a key and creates a corresponding
  value if not, suppressing checked exceptions. This method calls
  {@code createIfAbsent()}. If a {@link ConcurrentException} is thrown, it
  is caught and re-thrown as a {@link ConcurrentRuntimeException}.
  
  @param <K> the type of the keys of the map
  @param <V> the type of the values of the map
  @param map the map to be modified
  @param key the key of the value to be added
  @param init the {@link ConcurrentInitializer} for creating the value
  @return the value stored in the map after this operation; this may or may
  not be the object created by the {@link ConcurrentInitializer}
  @throws ConcurrentRuntimeException if the initializer throws an exception