Method copyOf

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

Returns an immutable map containing the same entries as {@code map}. The returned map iterates over entries in the same order as the {@code entrySet} of the original map. If {@code map} somehow contains entries with duplicate keys (for example, if it is a {@code 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(class="st">"unchecked") class="cm">// 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(class="st">"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