}

    /**
     * Checks if a previous page exists.
     * @return true if a previous page exists, false otherwise.
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets whether a previous page exists.
     * @param existPrePage true if a previous page exists, false otherwise.
     */

    }

    /**
     * Checks if a previous page exists.
     *
     * @return true if a previous page exists, false otherwise.
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets the flag for the existence of a previous page.
     *
     * @param existPrePage true if a previous page exists.
     */

/**
 * Serializes execution of tasks, somewhat like an "asynchronous {@code synchronized} block." Each
 * {@linkplain #submit enqueued} callable will not be submitted to its associated executor until the
 * previous callable has returned -- and, if the previous callable was an {@link AsyncCallable}, not
 * until the {@code Future} it returned is {@linkplain Future#isDone done} (successful, failed, or
 * cancelled).
 *

  public void fetch(HttpUrl url) throws IOException {
    // Skip hosts that we've visited many times.
    AtomicInteger hostnameCount = new AtomicInteger();
    AtomicInteger previous = hostnames.putIfAbsent(url.host(), hostnameCount);
    if (previous != null) hostnameCount = previous;
    if (hostnameCount.getAndIncrement() >= hostLimit) return;

    Request request = new Request.Builder()
        .url(url)
        .build();

  }

  @Override
  public final boolean hasPrevious() {
    return backingIterator().hasPrevious();
  }

  @Override
  @ParametricNullness
  public final T previous() {
    return transform(backingIterator().previous());
  }

  @Override
  public final int nextIndex() {
    return backingIterator().nextIndex();
  }

  @Override
  public final int previousIndex() {

  }

  @Override
  public final boolean hasPrevious() {
    return backingIterator().hasPrevious();
  }

  @Override
  @ParametricNullness
  public final T previous() {
    return transform(backingIterator().previous());
  }

  @Override
  public final int nextIndex() {
    return backingIterator().nextIndex();
  }

  @Override
  public final int previousIndex() {

# Classes as Dependencies { #classes-as-dependencies }

Before diving deeper into the **Dependency Injection** system, let's upgrade the previous example.

## A `dict` from the previous example { #a-dict-from-the-previous-example }

In the previous example, we were returning a `dict` from our dependency ("dependable"):

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[9] *}

    }

    /**
     * Checks if a previous page exists.
     *
     * @return true if a previous page exists, false otherwise
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets whether a previous page exists.
     *
     * @param existPrePage true if a previous page exists, false otherwise
     */

/// tip

Also, keep in mind that depending on your setup, in some cases you **might not even need any previous steps** before starting your application.

In that case, you wouldn't have to worry about any of this. 🤷

///

### Examples of Previous Steps Strategies { #examples-of-previous-steps-strategies }

    }

    /**
     * Checks if a previous page exists before the current page.
     *
     * @return true if a previous page exists, false otherwise
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets whether a previous page exists before the current page.
     *
     * @param existPrePage true if a previous page exists, false otherwise
     */