`kubeadm token create` or make the default token permanently valid by specifying
 `--token-ttl 0` to `kubeadm init`. The default token can later be deleted with
 `kubeadm token delete`.

 - `kubeadm join` now delegates TLS Bootstrapping to the kubelet itself, instead
 of reimplementing the process. `kubeadm join` writes the bootstrap kubeconfig
 file to `/etc/kubernetes/bootstrap-kubelet.conf`.

#### Defaults

  /**
   * Returns the backing delegate instance that methods are forwarded to. Abstract subclasses
   * generally override this method with an abstract method that has a more specific return type,
   * such as {@link ForwardingSet#delegate}. Concrete subclasses override this method to supply the
   * instance being decorated.
   */
  protected abstract Object delegate();

  /**
   * Returns the backing delegate instance that methods are forwarded to. Abstract subclasses
   * generally override this method with an abstract method that has a more specific return type,
   * such as {@link ForwardingSet#delegate}. Concrete subclasses override this method to supply the
   * instance being decorated.
   */
  protected abstract Object delegate();

  public static ListeningExecutorService listeningDecorator(ExecutorService delegate) {
    return (delegate instanceof ListeningExecutorService)
        ? (ListeningExecutorService) delegate
        : (delegate instanceof ScheduledExecutorService)
            ? new ScheduledListeningDecorator((ScheduledExecutorService) delegate)
            : new ListeningDecorator(delegate);
  }

  /**

   *
   * <p>If {@code delegate} is an instance created by an earlier call to {@code memoize}, it is
   * returned directly.
   */
  public static <T extends @Nullable Object> Supplier<T> memoize(Supplier<T> delegate) {
    if (delegate instanceof NonSerializableMemoizingSupplier
        || delegate instanceof MemoizingSupplier) {
      return delegate;
    }
    return delegate instanceof Serializable

   *
   * <p>If {@code delegate} is an instance created by an earlier call to {@code memoize}, it is
   * returned directly.
   */
  public static <T extends @Nullable Object> Supplier<T> memoize(Supplier<T> delegate) {
    if (delegate instanceof NonSerializableMemoizingSupplier
        || delegate instanceof MemoizingSupplier) {
      return delegate;
    }
    return delegate instanceof Serializable

      private val delegate: MutableIterator<DiskLruCache.Snapshot> = cache.snapshots()
      private var nextUrl: String? = null
      private var canRemove = false

      override fun hasNext(): Boolean {
        if (nextUrl != null) return true

        canRemove = false // Prevent delegate.remove() on the wrong item!
        while (delegate.hasNext()) {
          try {

  private static class SynchronizedObject implements Serializable {
    final Object delegate;
    final Object mutex;

    SynchronizedObject(Object delegate, @Nullable Object mutex) {
      this.delegate = checkNotNull(delegate);
      this.mutex = (mutex == null) ? this : mutex;
    }

    Object delegate() {
      return delegate;
    }

    // No equals and hashCode; see ForwardingObject for details.

  private static class SynchronizedObject implements Serializable {
    final Object delegate;
    final Object mutex;

    SynchronizedObject(Object delegate, @Nullable Object mutex) {
      this.delegate = checkNotNull(delegate);
      this.mutex = (mutex == null) ? this : mutex;
    }

    Object delegate() {
      return delegate;
    }

    // No equals and hashCode; see ForwardingObject for details.

    private final Deque<E> delegate = new LinkedList<>();
    private final Object mutex = new Object[0]; // something Serializable

    @Override
    public boolean offer(E o) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.offer(o);
    }

    @Override
    public @Nullable E poll() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.poll();
    }

    @Override