}

  /** Returns a joiner which automatically places {@code separator} between consecutive elements. */
  public static Joiner on(char separator) {
    return new Joiner(String.valueOf(separator));
  }

  private final String separator;

  private Joiner(String separator) {
    this.separator = checkNotNull(separator);
  }

  private Joiner(Joiner prototype) {
    this.separator = prototype.separator;
  }

  }

  private static final Joiner JOINER = Joiner.on(", ");

  @Override
  protected void assertMoreInvariants(Map<K, V> map) {
    // TODO: can these be moved to MapInterfaceTest?
    for (Entry<K, V> entry : map.entrySet()) {
      assertEquals(entry.getKey() + "=" + entry.getValue(), entry.toString());
    }

    assertEquals("{" + JOINER.join(map.entrySet()) + "}", map.toString());

  }

  private static void checkNoOutput(Joiner joiner, Iterable<Integer> set) {
    assertEquals("", joiner.join(set));
    assertEquals("", joiner.join(set.iterator()));

    Object[] array = newArrayList(set).toArray(new Integer[0]);
    assertEquals("", joiner.join(array));

    StringBuilder sb1FromIterable = new StringBuilder();
    assertSame(sb1FromIterable, joiner.appendTo(sb1FromIterable, set));

  }

  private static final Joiner JOINER = Joiner.on(", ");

  @Override
  protected final void assertMoreInvariants(Map<K, V> map) {
    // TODO: can these be moved to MapInterfaceTest?
    for (Entry<K, V> entry : map.entrySet()) {
      assertEquals(entry.getKey() + "=" + entry.getValue(), entry.toString());
    }

    assertEquals("{" + JOINER.join(map.entrySet()) + "}", map.toString());

  }

  private static void checkNoOutput(Joiner joiner, Iterable<Integer> set) {
    assertEquals("", joiner.join(set));
    assertEquals("", joiner.join(set.iterator()));

    Object[] array = newArrayList(set).toArray(new Integer[0]);
    assertEquals("", joiner.join(array));

    StringBuilder sb1FromIterable = new StringBuilder();
    assertSame(sb1FromIterable, joiner.appendTo(sb1FromIterable, set));

      assertEquals(entry.getKey(), bimap.inverse().get(entry.getValue()));
    }

    assertEquals("{" + JOINER.join(map.entrySet()) + "}", map.toString());
    assertEquals("[" + JOINER.join(map.entrySet()) + "]", map.entrySet().toString());
    assertEquals("[" + JOINER.join(map.keySet()) + "]", map.keySet().toString());
    assertEquals("[" + JOINER.join(map.values()) + "]", map.values().toString());

  }

  private static final Joiner JOINER = Joiner.on(", ");

  @Override
  protected void assertMoreInvariants(Map<K, V> map) {
    // TODO: can these be moved to MapInterfaceTest?
    for (Entry<K, V> entry : map.entrySet()) {
      assertEquals(entry.getKey() + "=" + entry.getValue(), entry.toString());
    }

    assertEquals("{" + JOINER.join(map.entrySet()) + "}", map.toString());

      assertEquals(entry.getKey(), bimap.inverse().get(entry.getValue()));
    }

    assertEquals("{" + JOINER.join(map.entrySet()) + "}", map.toString());
    assertEquals("[" + JOINER.join(map.entrySet()) + "]", map.entrySet().toString());
    assertEquals("[" + JOINER.join(map.keySet()) + "]", map.keySet().toString());
    assertEquals("[" + JOINER.join(map.values()) + "]", map.values().toString());

        TimeUnit unit,
        Class<?> cls,
        Joiner joiner,
        Pattern pattern,
        UnsignedInteger ui,
        UnsignedLong ul,
        StringBuilder sb,
        Predicate<?> pred,
        Function<?, ?> func,
        Object obj) {
      delegate.foo(
          s, r, n, it, b, eq, e, in, c, ord, charset, unit, cls, joiner, pattern, ui, ul, sb, pred,
          func, obj);
    }

        }
        String prefix = (moduleName == null) ? "" : (moduleName + '=');
        StringJoiner joiner = new StringJoiner(File.pathSeparator, prefix, "");
        joiner.setEmptyValue("");
        for (Path p : paths) {
            joiner.add(p.toString());
        }
        String value = joiner.toString();
        if (value.isEmpty()) {
            return new String[0];
        }