Method getOnlyElement

output/java_guava/1.4.18/Iterators.java:320–337

Returns the single element contained in iterator. @throws NoSuchElementException if the iterator is empty @throws IllegalArgumentException if the iterator contains multiple elements. The state of the iterator is unspecified.

(Iterator<T> iterator)

   */

  @CanIgnoreReturnValue // TODO(kak): Consider removing this?
  public static <T> T getOnlyElement(Iterator<T> iterator) {
    T first = iterator.next();
    if (!iterator.hasNext()) {
      return first;
    }
    StringBuilder sb = new StringBuilder();
    sb.append("expected one element but was: <" + first);
    for (int i = 0; i < 4 && iterator.hasNext(); i++) {
      sb.append(", " + iterator.next());
    }
    if (iterator.hasNext()) {
      sb.append(", ...");
    }

    sb.append('>');
    throw new IllegalArgumentException(sb.toString());
  }

  /**
   * Returns the single element contained in {@code iterator}, or {@code