* Normally used as a C string terminator.
   *
   * <p>Although RFC 20 names this as "Null", note that it is distinct from the C/C++ "NULL"
   * pointer.
   *
   * @since 8.0
   */
  public static final byte NUL = 0;

  /**
   * Start of Heading: A communication control character used at the beginning of a sequence of

2.5em;padding-left:0}.form-switch.form-check-reverse .form-check-input{margin-right:-2.5em;margin-left:0}.form-check-inline{display:inline-block;margin-right:1rem}.btn-check{position:absolute;clip:rect(0,0,0,0);pointer-events:none}.btn-check:disabled+.btn,.btn-check[disabled]+.btn{pointer-events:none;filter:none;opacity:.65}[data-bs-theme=dark] .form-switch .form-check-input:not(:checked):not(:focus){--bs-form-switch-bg:url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='-4...

:hover{color:#212529;text-decoration:none}.btn.focus,.btn:focus{outline:0;box-shadow:0 0 0 .2rem rgba(0,123,255,.25)}.btn.disabled,.btn:disabled{opacity:.65}.btn:not(:disabled):not(.disabled){cursor:pointer}a.btn.disabled,fieldset:disabled a.btn{pointer-events:none}.btn-primary{color:#fff;background-color:#007bff;border-color:#007bff}.btn-primary:hover{color:#fff;background-color:#0069d9;border-color:#0062cc}.btn-primary.focus,.btn-primary:focus{color:#fff;background-color:#0069d9;border-color:#0062cc;box-shadow:0...

box-shadow(none);\n  }\n\n  &:not(:disabled):not(.disabled) {\n    cursor: if($enable-pointer-cursor-for-buttons, pointer, null);\n\n    &:active,\n    &.active {\n      @include box-shadow($btn-active-box-shadow);\n\n      &:focus {\n        @include box-shadow($btn-focus-box-shadow, $btn-active-box-shadow);\n      }\n    }\n  }\n}\n\n// Future-proof disabling of clicks on `<a>` elements\na.btn.disabled,\nfieldset:disabled a.btn {\n  pointer-events: none;\n}\n\n\n//\n// Alternate buttons\n//\n\n@each $color, $value...

   */
  protected final <T> void setDefault(Class<T> type, T value) {
    tester.setDefault(type, value);
  }

  /**
   * Sets two distinct values for {@code type}. These values can be used for both null pointer
   * testing and equals testing.
   *
   * @since 17.0
   */
  protected final <T> void setDistinctValues(Class<T> type, T value1, T value2) {
    tester.setDistinctValues(type, value1, value2);
  }

        this.runnable = runnable;
        this.executor = executor;
        this.next = next;
      }
    }
  }

  // A version of the ExecutionList that uses an explicit tail pointer to keep the nodes in order
  // rather than flipping the stack in execute().
  private static final class NewExecutionListQueue {
    static final Logger log = Logger.getLogger(NewExecutionListQueue.class.getName());

because ul and ol\n  margin-bottom: 0;\n  @include border-radius(var(--#{$prefix}list-group-border-radius));\n}\n\n.list-group-numbered {\n  list-style-type: none;\n  counter-reset: section;\n\n  > .list-group-item::before {\n    // Increments only this instance of the section counter\n    content: counters(section, \".\") \". \";\n    counter-increment: section;\n  }\n}\n\n// Interactive list items\n//\n// Use anchor or button elements instead of `li`s or `div`s to create interactive\n// list items. Includes...

   * the first duplicate.
   */

  // This entry point is for callers other than ImmutableMap.Builder.
  static <K, V> RegularImmutableMap<K, V> create(
      int n, @Nullable Object[] alternatingKeysAndValues) {
    return create(n, alternatingKeysAndValues, /* builder= */ null);
  }

  // This entry point is used by the other create method but also directly by

   * ServiceManager} constructor without having to close over the partially constructed {@link
   * ServiceManager} instance (i.e. avoid leaking a pointer to {@code this}).
   */
  private final ServiceManagerState state;

  private final ImmutableList<Service> services;

  /**
   * Constructs a new instance for managing the given services.
   *

  private ExecutionSequencer() {}

  /** Creates a new instance. */
  public static ExecutionSequencer create() {
    return new ExecutionSequencer();
  }

  /** This reference acts as a pointer tracking the head of a linked list of ListenableFutures. */
  private final AtomicReference<ListenableFuture<@Nullable Void>> ref =
      new AtomicReference<>(immediateVoidFuture());