return (input.length() > 0) && (input.charAt(0) == 'a');
        }
      };

  @SuppressWarnings("UnnecessaryStringBuilder") // false positive in a weird case
  public void testIndexOf_genericPredicate() {
    List<CharSequence> sequences = new ArrayList<>();
    sequences.add("bob");
    sequences.add(new StringBuilder("charlie"));
    sequences.add(new StringBuilder("henry"));