Method copyOf

guava/src/com/google/common/collect/ImmutableMap.java:687–713

Returns an immutable map containing the same entries as map. The returned map iterates over entries in the same order as the entrySet of the original map. If map somehow contains entries with duplicate keys (for example, if it is a SortedMap whose comparator is not <i

(Map<? extends K, ? extends V> map)

   * @throws NullPointerException if any key or value in {@code map} is null
   */
  public static <K, V> ImmutableMap<K, V> copyOf(Map<? extends K, ? extends V> map) {
    if ((map instanceof ImmutableMap) && !(map instanceof SortedMap)) {
      @SuppressWarnings("unchecked") // safe since map is not writable
      ImmutableMap<K, V> kvMap = (ImmutableMap<K, V>) map;
      if (!kvMap.isPartialView()) {
        return kvMap;
      }
    } else if (map instanceof EnumMap) {
      EnumMap<?, ? extends V> clone = ((EnumMap<?, ? extends V>) map).clone();
      for (Entry<?, ?> entry : clone.entrySet()) {
        checkEntryNotNull(entry.getKey(), entry.getValue());
      }
      ImmutableMap<?, ? extends V> untypedResult = ImmutableEnumMap.asImmutable(clone);
      /*
       * The result has the same type argument we started with. We just couldn't express EnumMap<K,
       * ...> or ImmutableEnumMap<K, ...> along the way because our own <K> isn't <K extends
       * Enum<K>>.
       *
       * We are also performing a covariant cast, potentially from ImmutableMap<K, Sub> to
       * ImmutableMap<K, Super>. That is safe because no one can add elements to the map.
       */
      @SuppressWarnings("unchecked")
      ImmutableMap<K, V> result = (ImmutableMap<K, V>) untypedResult;
      return result;
    }
    return copyOf(map.entrySet());
  }

  /**
   * Returns an immutable map containing the specified entries. The returned map iterates over