guava/src/com/google/common/base/Joiner.java
@CanIgnoreReturnValue
  public final StringBuilder appendTo(StringBuilder builder, Iterable<?> parts) {
    return appendTo(builder, parts.iterator());
  }
@CanIgnoreReturnValue
  public final StringBuilder appendTo(StringBuilder builder, Iterable<?> parts) {
    return appendTo(builder, parts.iterator());
  }
Appends the string representation of each of {@code parts}, using the previously configured
separator between each, to {@code builder}. Identical to {@link #appendTo(Appendable,
Iterable)}, except that it does not throw {@link IOException}.