Method construct

output/java_guava/1.4.18/ImmutableSet.java:148–196

Constructs an ImmutableSet from the first n elements of the specified array. If k is the size of the returned ImmutableSet, then the unique elements of elements will be in the first k positions, and elements[i] == null for k <= i < n.

(int n, Object... elements)

   */

  private static <E> ImmutableSet<E> construct(int n, Object... elements) {
    switch (n) {
      case 0:
        return of();
      case 1:
        @SuppressWarnings("unchecked") // safe; elements contains only E's
        E elem = (E) elements[0];
        return of(elem);
      default:
        // continue below to handle the general case

    }
    int tableSize = chooseTableSize(n);
    Object[] table = new Object[tableSize];
    int mask = tableSize - 1;
    int hashCode = 0;
    int uniques = 0;
    for (int i = 0; i < n; i++) {
      Object element = checkElementNotNull(elements[i], i);
      int hash = element.hashCode();
      for (int j = Hashing.smear(hash); ; j++) {
        int index = j & mask;
        Object value = table[index];
        if (value == null) {
          // Came to an empty slot. Put the element here.
          elements[uniques++] = element;
          table[index] = element;
          hashCode += hash;
          break;
        } else if (value.equals(element)) {
          break;
        }
      }
    }
    Arrays.fill(elements, uniques, n, null);
    if (uniques == 1) {
      // There is only one element or elements are all duplicates
      @SuppressWarnings("unchecked") // we are careful to only pass in E
      E element = (E) elements[0];
      return new SingletonImmutableSet<E>(element, hashCode);
    } else if (tableSize != chooseTableSize(uniques)) {
      // Resize the table when the array includes too many duplicates.
      // when this happens, we have already made a copy
      return construct(uniques, elements);
    } else {
      Object[] uniqueElements = (uniques < elements.length) ? ObjectArrays.arraysCopyOf(elements, uniques) : elements;
      return new RegularImmutableSet<E>(uniqueElements, hashCode, table, mask);
    }
  }

  // We use power-of-2 tables, and this is the highest int that's a power of 2