*
 * <h3>Building a {@code ValueGraph}</h3>
 *
 * <p>The implementation classes that {@code common.graph} provides are not public, by design. To
 * create an instance of one of the built-in implementations of {@code ValueGraph}, use the {@link
 * ValueGraphBuilder} class:
 *
 * {@snippet :
 * MutableValueGraph<Integer, Double> graph = ValueGraphBuilder.directed().build();
 * }
 *

```Python hl_lines="1"
{!> ../../docs_src/python_types/tutorial009_py310.py!}
```

////

使用 `str | None` 而不是仅仅 `str`，可以让编辑器帮助你发现把值当成总是 `str` 的错误（实际上它也可能是 `None`）。

### 类作为类型 { #classes-as-types }

你也可以把类声明为变量的类型。

假设你有一个名为 `Person` 的类，带有 name：

{* ../../docs_src/python_types/tutorial010_py310.py hl[1:3] *}

然后你可以声明一个变量是 `Person` 类型：

  @Override
  @J2ktIncompatible
  @GwtIncompatible
    Object writeReplace() {
    return super.writeReplace();
  }

  // This class is never actually serialized directly, but we have to make the
  // warning go away (and suppressing would suppress for all nested classes too)
  @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;

 * all elements in priority order and place them in another collection.
 *
 * <p>Operations on this class make no guarantees about the ordering of elements with equal
 * priority. If you need to enforce an ordering, you can define custom classes or comparators that
 * use a secondary key to break ties in primary priority values. For example, here is a class that
 * applies first-in-first-out tie-breaking to comparable elements. To use it, you would insert a

 *
 * <h3>Building a {@code Graph}</h3>
 *
 * <p>The implementation classes that {@code common.graph} provides are not public, by design. To
 * create an instance of one of the built-in implementations of {@code Graph}, use the {@link
 * GraphBuilder} class:
 *
 * {@snippet :
 * MutableGraph<Integer> graph = GraphBuilder.undirected().build();
 * }
 *

 * com.google.common.base.Function, java.util.concurrent.Executor) Futures.transform} and {@link
 * Futures#catching(ListenableFuture, Class, com.google.common.base.Function,
 * java.util.concurrent.Executor) Futures.catching}.
 *
 * <p>This class implements all methods in {@code ListenableFuture}. Subclasses should provide a way
 * to set the result of the computation through the protected methods {@link #set(Object)}, {@link

import org.jspecify.annotations.Nullable;

/**
 * Static utility methods pertaining to {@link Queue} and {@link Deque} instances. Also see this
 * class's counterparts {@link Lists}, {@link Sets}, and {@link Maps}.
 *
 * @author Kurt Alfred Kluever
 * @since 11.0
 */
@GwtCompatible
public final class Queues {
  private Queues() {}

  // ArrayBlockingQueue

  /**

import org.codehaus.plexus.util.xml.pull.XmlPullParserException;

/**
 * Class CoreExtensionsXpp3Reader.
 *
 * @deprecated use {@code org.apache.maven.cling.internal.extension.io.CoreExtensionsStaxReader}
 */
@Deprecated
@SuppressWarnings("all")
public class CoreExtensionsXpp3Reader {

    // --------------------------/
    // - Class/Member Variables -/
    // --------------------------/

    /**

  /*
   * This class is used to serialize all ImmutableSortedSet instances,
   * regardless of implementation type. It captures their "logical contents"
   * only. This is necessary to ensure that the existence of a particular
   * implementation type is an implementation detail.
   */
  @J2ktIncompatible // serialization
  private static final class SerializedForm<E> implements Serializable {

* For error messages related changes, follow the [ErrorMessages Guide](contributing/ErrorMessages.md).
* Add Javadoc for new methods and classes, following the [Javadoc Style Guide](contributing/JavadocStyleGuide.md). Javadoc is *required* for new public, top-level types.